{"id":6544,"date":"2026-08-30T12:00:16","date_gmt":"2026-08-30T12:00:16","guid":{"rendered":"https:\/\/bbpmfg.com\/?p=6544"},"modified":"2026-08-30T13:36:17","modified_gmt":"2026-08-30T13:36:17","slug":"pump-efficiency-formula","status":"publish","type":"post","link":"https:\/\/bbpmfg.com\/ar\/blog\/pump-efficiency-formula\/","title":{"rendered":"\u0645\u0639\u0627\u062f\u0644\u0629 \u0643\u0641\u0627\u0621\u0629 \u0627\u0644\u0645\u0636\u062e\u0629: \u062d\u0633\u0627\u0628 \u0627\u0644\u0643\u0641\u0627\u0621\u0629 \u0627\u0644\u0647\u064a\u062f\u0631\u0648\u0644\u064a\u0643\u064a\u0629 \u0648\u0643\u0641\u0627\u0621\u0629 \u0639\u0645\u0648\u062f \u0627\u0644\u062f\u0648\u0631\u0627\u0646 \u0648\u0627\u0644\u0643\u0641\u0627\u0621\u0629 \u0627\u0644\u0625\u062c\u0645\u0627\u0644\u064a\u0629"},"content":{"rendered":"<div class=\"seo-blog-content\" style=\"padding:1px 0;\">\r\n<p style=\"margin:0 0 20px; font-size:1.05em;\">The pump efficiency formula is useful hydraulic output power divided by input power, multiplied by 100%. The arithmetic is short. The important part is choosing the right input boundary: shaft power for the bare pump, or electrical power for the complete motor-and-pump system. This guide shows both methods, works the same duty point in metric and US units, and explains how to check a result before comparing it with a curve.<\/p>\n<div style=\"margin:0 0 24px; padding:20px 24px; background:#f5f5f5; border:1px solid #e0e0e0; border-top:3px solid #2d2d2d;\">\r\n<h3 style=\"margin:0 0 14px;\">Quick Answer<\/h3>\r\n<p style=\"margin:0 0 8px;\"><strong>Pump-only efficiency:<\/strong> \u03b7<sub>pump<\/sub> = P<sub>hydraulic<\/sub> \u00f7 P<sub>shaft<\/sub> \u00d7 100%<\/p>\r\n<p style=\"margin:0 0 8px;\"><strong>Wire-to-water efficiency:<\/strong> \u03b7<sub>wire-to-water<\/sub> = P<sub>hydraulic<\/sub> \u00f7 P<sub>electrical input<\/sub> \u00d7 100%<\/p>\n<p style=\"margin:0;\"><strong>Hydraulic output:<\/strong> P<sub>hydraulic<\/sub> = \u03c1gQH. For water, P<sub>hydraulic<\/sub> (kW) \u2248 Q (m\u00b3\/h) \u00d7 H (m) \u00f7 367.<\/p>\n<\/div>\n<p>Searches for a water pump efficiency formula, centrifugal pump efficiency formula, pump efficiency equation, or wire to water efficiency all lead to the same first decision: define the input boundary. That decision remains outside a pump efficiency formula calculator; the calculator only evaluates the values and units supplied.<\/p><!-- ecc-calc:begin tool=\"pump-efficiency-primary\" sha256=\"a9c181ea52aa508540887690d5539df3efe107cc28f33b8ea55548e546592f64\" -->\n\n<style data-calc-scope=\"pump-efficiency-primary\">#calc-pump-efficiency-primary{margin:26px 0;padding:18px;border:1px solid #c9d4de;border-radius:10px;background:#f8fbfd;color:#17324a;font-family:inherit}#calc-pump-efficiency-primary .ecc-calc__title{display:block;margin:0 0 6px;font-size:1.08rem;font-weight:700}#calc-pump-efficiency-primary .ecc-calc__intro{margin:0 0 14px;font-size:.92rem;line-height:1.5;color:#42566a}#calc-pump-efficiency-primary .ecc-calc__grid{display:grid;gap:12px;grid-template-columns:minmax(0,1fr)}#calc-pump-efficiency-primary .ecc-calc__field{display:grid;gap:5px}#calc-pump-efficiency-primary .ecc-calc__label{font-size:.82rem;font-weight:700;color:#42566a}#calc-pump-efficiency-primary .ecc-calc__value,#calc-pump-efficiency-primary .ecc-calc__unit,#calc-pump-efficiency-primary .ecc-calc__swap{min-height:42px;border:1px solid #aebdca;border-radius:6px;background:#fff;color:#17324a;font:inherit}#calc-pump-efficiency-primary .ecc-calc__value,#calc-pump-efficiency-primary .ecc-calc__unit{padding:8px 10px}#calc-pump-efficiency-primary .ecc-calc__swap{padding:8px 12px;cursor:pointer;font-weight:700}#calc-pump-efficiency-primary .ecc-calc__swap:focus,#calc-pump-efficiency-primary .ecc-calc__value:focus,#calc-pump-efficiency-primary .ecc-calc__unit:focus{outline:2px solid #1d6f9b;outline-offset:2px}#calc-pump-efficiency-primary .ecc-calc__panel{margin-top:16px;padding:12px;border-left:4px solid #1d6f9b;background:#eef6fa}#calc-pump-efficiency-primary .ecc-calc__panel-label{display:block;font-size:.74rem;letter-spacing:.08em;text-transform:uppercase;color:#42566a}#calc-pump-efficiency-primary .ecc-calc__out{display:flex;flex-wrap:wrap;align-items:baseline;gap:6px;margin-top:4px}#calc-pump-efficiency-primary .ecc-calc__result{font-size:1.3rem;font-weight:700;font-variant-numeric:tabular-nums}#calc-pump-efficiency-primary .ecc-calc__symbol{font-size:1rem;font-weight:700;color:#42566a}#calc-pump-efficiency-primary .ecc-calc__restate{margin:6px 0 0;font-size:.84rem;color:#42566a}#calc-pump-efficiency-primary .ecc-calc__note{margin:10px 0 0;font-size:.82rem;line-height:1.5;color:#42566a}@media (min-width:720px){#calc-pump-efficiency-primary .ecc-calc__grid{grid-template-columns:minmax(0,1.2fr) minmax(0,1fr) auto minmax(0,1fr);align-items:end}}<\/style>\n<section id=\"calc-pump-efficiency-primary\" class=\"ecc-calc\" data-calc-tool=\"pump-efficiency-primary\" data-calc-kind=\"formula\" data-calc-formula=\"pump_efficiency_percent\" data-calc-decimals=\"2\">\n<p class=\"ecc-calc__title\">Pump efficiency from flow, total head and measured input power<\/p>\n<p class=\"ecc-calc__intro\">Pump efficiency is hydraulic power divided by measured input power. With flow in m\u00b3\/h, total head in m, density in kg\/m\u00b3 and input in kW, first convert flow to m\u00b3\/s, calculate P_h = \u03c1gQH in W, then divide by input W and express the ratio as a percent.<\/p>\n<div class=\"ecc-calc__grid\">\n<label class=\"ecc-calc__field\" for=\"calc-pump-efficiency-primary-in-flow\"><span class=\"ecc-calc__label\">Flow rate <span class=\"ecc-calc__label-unit\">(m\u00b3\/h)<\/span><\/span><input id=\"calc-pump-efficiency-primary-in-flow\" class=\"ecc-calc__value\" type=\"text\" inputmode=\"decimal\" maxlength=\"64\" value=\"100\" min=\"0.0\" max=\"1000000.0\" aria-label=\"Flow rate\"><\/label>\n<label class=\"ecc-calc__field\" for=\"calc-pump-efficiency-primary-in-head\"><span class=\"ecc-calc__label\">Total head <span class=\"ecc-calc__label-unit\">(m)<\/span><\/span><input id=\"calc-pump-efficiency-primary-in-head\" class=\"ecc-calc__value\" type=\"text\" inputmode=\"decimal\" maxlength=\"64\" value=\"30\" min=\"0.0\" max=\"100000.0\" aria-label=\"Total head\"><\/label>\n<label class=\"ecc-calc__field\" for=\"calc-pump-efficiency-primary-in-density\"><span class=\"ecc-calc__label\">Liquid density <span class=\"ecc-calc__label-unit\">(kg\/m\u00b3)<\/span><\/span><input id=\"calc-pump-efficiency-primary-in-density\" class=\"ecc-calc__value\" type=\"text\" inputmode=\"decimal\" maxlength=\"64\" value=\"1000\" min=\"0.0\" max=\"100000.0\" aria-label=\"Liquid density\"><\/label>\n<label class=\"ecc-calc__field\" for=\"calc-pump-efficiency-primary-in-input_kw\"><span class=\"ecc-calc__label\">Measured input power <span class=\"ecc-calc__label-unit\">(kW)<\/span><\/span><input id=\"calc-pump-efficiency-primary-in-input_kw\" class=\"ecc-calc__value\" type=\"text\" inputmode=\"decimal\" maxlength=\"64\" value=\"13\" min=\"0.001\" max=\"1000000.0\" aria-label=\"Measured input power\"><\/label>\n<\/div>\n<div class=\"ecc-calc__panel\">\n<span class=\"ecc-calc__panel-label\">Pump efficiency<\/span>\n<div class=\"ecc-calc__out\"><output id=\"calc-pump-efficiency-primary-result\" class=\"ecc-calc__result\" aria-live=\"polite\">62.86<\/output><span id=\"calc-pump-efficiency-primary-unit\" class=\"ecc-calc__symbol\">%<\/span><\/div>\n<p id=\"calc-pump-efficiency-primary-restate\" class=\"ecc-calc__restate\">Use readings from the same duty point. Shaft input gives pump-only efficiency; electrical or supply input gives overall (wire-to-water) efficiency.<\/p>\n<\/div>\n<p id=\"calc-pump-efficiency-primary-note\" class=\"ecc-calc__note\">Use readings from the same duty point. Shaft input gives pump-only efficiency; electrical or supply input gives overall (wire-to-water) efficiency.<\/p>\n<\/section>\n<script data-tool-core=\"1\" data-no-optimize=\"1\" data-cfasync=\"false\">(()=>{'use strict';const MAX_ABS_INPUT=1000000000000000.0;const DEFAULT_DECIMALS=2;const SIG_FALLBACK=6;const NUMERIC_RE=\/^[+-]?(?:\\d+(?:\\.\\d*)?|\\.\\d+)$\/;const INPUTS=[\"flow\", \"head\", \"density\", \"input_kw\"];const INPUT_LIMITS=[{\"min\":0.0,\"max\":1000000.0},{\"min\":0.0,\"max\":100000.0},{\"min\":0.0,\"max\":100000.0},{\"min\":0.001,\"max\":1000000.0}];const CONSTS={\"cubic_metre_per_second_per_cubic_metre_per_hour\": 0.0002777777777777778, \"standard_gravity_m_per_s2\": 9.80665, \"watts_per_kilowatt\": 1000.0};function withinInputLimits(value,index){var limits=INPUT_LIMITS[index];return !limits?true:(value>=limits.min?(value<=limits.max):false);}function parseInput(raw,index){if(raw===null||raw===undefined)return null;if(typeof raw==='number'){return (Number.isFinite(raw)?(Math.abs(raw)<=MAX_ABS_INPUT?withinInputLimits(raw,index):false):false)?raw:null;}if(typeof raw!=='string')return null;if(raw.length>64)return null;var text=raw.replace(\/^[\\t-\\r \\u00a0\\u1680\\u2000-\\u200a\\u2028\\u2029\\u202f\\u205f\\u3000\\ufeff]+|[\\t-\\r \\u00a0\\u1680\\u2000-\\u200a\\u2028\\u2029\\u202f\\u205f\\u3000\\ufeff]+$\/g,'');if(\/[\\t-\\r \\u00a0\\u1680\\u2000-\\u200a\\u2028\\u2029\\u202f\\u205f\\u3000\\ufeff]\/.test(text))return null;if(text===''||!NUMERIC_RE.test(text))return null;var value=Number(text);if(!Number.isFinite(value)||Math.abs(value)>MAX_ABS_INPUT||!withinInputLimits(value,index))return null;return value;}function compute(){var args=Array.prototype.slice.call(arguments);if(args.length!==INPUTS.length)return null;for(var i=0;i<args.length;i++){var a=args[i];if(typeof a!=='number'||!Number.isFinite(a)||Math.abs(a)>MAX_ABS_INPUT||!withinInputLimits(a,i))return null;}var flow=args[0];var head=args[1];var density=args[2];var input_kw=args[3];var cubic_metre_per_second_per_cubic_metre_per_hour=CONSTS[\"cubic_metre_per_second_per_cubic_metre_per_hour\"];var standard_gravity_m_per_s2=CONSTS[\"standard_gravity_m_per_s2\"];var watts_per_kilowatt=CONSTS[\"watts_per_kilowatt\"];const flow_m3s=(flow*cubic_metre_per_second_per_cubic_metre_per_hour);const hydraulic_w=(((density*standard_gravity_m_per_s2)*flow_m3s)*head);const input_w=(input_kw*watts_per_kilowatt);const percent=((input_w>0)?((hydraulic_w\/input_w)*100):0);return Number.isFinite(percent)?percent:null;}function trimZeros(text){if(text.indexOf('.')===-1)return text;text=text.replace(\/0+$\/,'').replace(\/\\.$\/,'');return (text===''||text==='-'||text==='-0')?'0':text;}function formatResult(value,decimals){if(value===null||value===undefined||typeof value!=='number')return '';if(!Number.isFinite(value))return '';var d=decimals;if(typeof d!=='number'||!Number.isFinite(d)||Math.floor(d)!==d||d<0||d>10){d=DEFAULT_DECIMALS;}if(value!==0?Math.abs(value)<Math.pow(10,-d):false){var precise=value.toPrecision(SIG_FALLBACK);return precise.indexOf('e')===-1?trimZeros(precise):precise;}if(Math.abs(value)>=1e21)return String(value);return trimZeros(value.toFixed(d));}var API={parseInput:parseInput,compute:compute,formatResult:formatResult,INPUTS:INPUTS,INPUT_LIMITS:INPUT_LIMITS,CONSTS:CONSTS};if(typeof globalThis.document==='undefined'){globalThis.__TOOL_CORE__=API;}else{Object.defineProperty(globalThis,\"__ECC_CALC_CORE_pump_efficiency_primary__\",{value:API,configurable:true});}})();<\/script>\n<script data-tool-binding=\"1\" data-no-optimize=\"1\" data-cfasync=\"false\">(()=>{'use strict';const root=document.getElementById('calc-pump-efficiency-primary');if(!root||root.id!=='calc-pump-efficiency-primary'||root.getAttribute('data-calc-tool')!=='pump-efficiency-primary')return;const HANDOFF=\"__ECC_CALC_CORE_pump_efficiency_primary__\";const CORE=globalThis[HANDOFF];if(!CORE)return;delete globalThis[HANDOFF];Object.defineProperty(root,'__eccCalcCore__',{value:CORE,configurable:true});const pick=(suffix)=>root.querySelector('#calc-pump-efficiency-primary-'+suffix);const fields=CORE.INPUTS.map((name)=>pick('in-'+name));const resultEl=pick('result'),unitEl=pick('unit'),restateEl=pick('restate');const owns=(el)=>el?root.contains(el):false;if(!owns(resultEl))return;if(fields.some((el)=>!owns(el)))return;if(unitEl?!owns(unitEl):false)return;if(restateEl?!owns(restateEl):false)return;const declared=parseInt(root.getAttribute('data-calc-decimals'),10);const DECIMALS=Number.isFinite(declared)?declared:2;const render=()=>{const values=fields.map((el,index)=>CORE.parseInput(el.value,index));const bad=values.some((v)=>v===null);const out=bad?null:CORE.compute.apply(null,values);const text=CORE.formatResult(out,DECIMALS);resultEl.textContent=text===''?'\u2014':text;if(unitEl)unitEl.textContent='%';if(restateEl)restateEl.textContent=text===''?'Enter every value to see the result.':'Use readings from the same duty point. Shaft input gives pump-only efficiency; electrical or supply input gives overall (wire-to-water) efficiency.';};fields.forEach((el)=>{el.addEventListener('input',render);el.addEventListener('change',render);});render();})();<\/script>\n\n<!-- ecc-calc:end tool=\"pump-efficiency-primary\" -->\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">Which Efficiency Are You Calculating?<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_01.png\" alt=\"Which Efficiency Are You Calculating? \u2014 BBP\" class=\"wp-image-6534\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_01.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_01-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_01-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_01-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_01-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n<p>Before entering a number, draw the boundary around the equipment included in the calculation. That is the <strong>Measurement-Boundary Check<\/strong>. Two calculations may use the same hydraulic output and produce different, equally valid percentages because one stops at the pump shaft and the other starts at the electrical supply.<\/p>\n<div style=\"margin:24px 0; overflow-x:auto;\"><table style=\"width:100%; border-collapse:collapse; border:1px solid #e0e0e0;\"><caption style=\"caption-side:top; text-align:left; font-weight:600; padding:8px 0;\">Choose the denominator that matches the efficiency boundary.<\/caption><thead><tr style=\"background:#2d2d2d; color:#fff;\"><th scope=\"col\" style=\"padding:12px; text-align:left;\">Reported efficiency<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">Useful output<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">Input denominator<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">What it includes<\/th><\/tr><\/thead><tbody>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Pump-only<\/td><td style=\"padding:12px;\">Hydraulic power<\/td><td style=\"padding:12px;\">Measured shaft power<\/td><td style=\"padding:12px;\">Hydraulic, volumetric, and mechanical losses inside the pump<\/td><\/tr>\r\n<tr style=\"background:#f5f5f5; border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Pump + motor<\/td><td style=\"padding:12px;\">Hydraulic power<\/td><td style=\"padding:12px;\">Motor electrical input<\/td><td style=\"padding:12px;\">Pump losses plus motor losses<\/td><\/tr>\r\n<tr><td style=\"padding:12px;\">Wire-to-water system<\/td><td style=\"padding:12px;\">Hydraulic power<\/td><td style=\"padding:12px;\">Measured supply input<\/td><td style=\"padding:12px;\">Pump, motor, drive, and any included control losses<\/td><\/tr>\r\n<\/tbody><\/table><\/div>\r\n<p>The adjective \u201coverall\u201d is not enough to identify a boundary. Some <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">pump literature<\/a> uses overall efficiency for hydraulic output divided by shaft input. Energy regulations may use a driver-input or multi-load-point metric. Name the numerator and denominator every time.<\/p>\n<h3 style=\"margin:28px 0 10px;\">Which Input Reading Belongs in the Denominator?<\/h3>\n<p>One quick way to avoid the wrong denominator is to trace energy from the electrical supply to the electric motor, from motor shaft torque to the pump, and from the impeller to the liquid. Stop the map at the point where your input was actually measured. A shaft-torque reading belongs to a pump-only equation. A three-phase power-analyzer reading belongs to an overall or wire-to-water equation. A motor nameplate belongs to neither unless the task is rating selection rather than measurement.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">Step 1: Calculate Hydraulic Output Power<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_02.png\" alt=\"Step 1: Calculate Hydraulic Output Power \u2014 BBP\" class=\"wp-image-6535\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_02.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_02-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_02-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_02-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_02-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\r\n<p>Hydraulic power is the useful rate of energy delivered to the liquid:<\/p>\n<p style=\"padding:16px 20px; background:#f5f5f5; border-left:3px solid #2d2d2d;\"><strong>P<sub>hydraulic<\/sub> = \u03c1 \u00d7 g \u00d7 Q \u00d7 H<\/strong><\/p>\r\n<p>Here, \u03c1 is liquid density in kg\/m\u00b3, g is gravitational acceleration in m\/s\u00b2, Q is flow in m\u00b3\/s, and H is total dynamic head in metres. The result is watts. For water near ordinary test temperatures, the common metric shortcut is:<\/p>\n<p style=\"padding:16px 20px; background:#f5f5f5; border-left:3px solid #2d2d2d;\"><strong>P<sub>hydraulic<\/sub> (kW) \u2248 Q (m\u00b3\/h) \u00d7 H (m) \u00d7 SG \u00f7 367<\/strong><\/p>\r\n<p>Specific gravity, SG, accounts for liquid density relative to water. The constant 367 is a rounded unit-conversion shortcut, not a new physical law. If density and temperature matter to the required precision, use \u03c1gQH with the measured density instead.<\/p>\r\n<p>In US customary units, water horsepower is:<\/p>\r\n<p style=\"padding:16px 20px; background:#f5f5f5; border-left:3px solid #2d2d2d;\"><strong>Water horsepower = Q (gpm) \u00d7 H (ft) \u00d7 SG \u00f7 3,960<\/strong><\/p>\n<p>Use total dynamic head, not discharge pressure alone. Total head accounts for the pressure difference between discharge and suction, elevation terms, and velocity-head differences at the measurement sections. When gauges use different diameters or elevations, a simple pressure subtraction can be incomplete.<\/p>\n<p>Head is energy per unit weight, which is why the same <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">centrifugal pump curve<\/a> can express head independently of liquid density while power changes with density. Pressure and head are related, but they are not interchangeable without the liquid\u2019s density. This distinction becomes especially important when a water-tested pump is evaluated on a denser or lighter process liquid.<\/p>\n<blockquote style=\"margin:24px 0; padding:16px 20px; background:#f5f5f5; border-left:3px solid #2d2d2d;\"><p style=\"margin:0;\">Use output and input readings from the same stabilized duty point. Mixing a current flow-and-head reading with catalog peak power does not describe measured pump efficiency.<\/p><\/blockquote>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">Step 2: Identify Shaft or Electrical Input Power<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_03.png\" alt=\"Step 2: Identify Shaft or Electrical Input Power \u2014 BBP\" class=\"wp-image-6536\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_03.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_03-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_03-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_03-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_03-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n<p>For pump-only efficiency, the denominator is shaft input power at the measured duty point. Torque and rotational speed can establish it directly, or a <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">test report<\/a> may provide brake power for the same pump, impeller diameter, speed, and liquid. The motor nameplate rating is capacity information; it is not a live shaft-power reading.<\/p>\n<p>For wire-to-water efficiency, measure real electrical input power. On a three-phase motor, that normally means a suitable power analyzer that accounts for voltage, current, power factor, phase balance, waveform, and any variable-frequency drive inside the chosen boundary. Multiplying nameplate voltage and current is not a reliable substitute.<\/p>\n<p>One common field error is a boundary mismatch: motor nameplate capacity is used as though it were measured input. For example, a 15 kW nameplate does not prove that the shaft received 15 kW at the recorded duty point. Keep the torque-and-speed record or the power-analyzer export with the calculation so the denominator can be checked later.<\/p>\n<p>If your task is to size a motor rather than calculate a measured efficiency, use BBP\u2019s broader <a href=\"https:\/\/bbpmfg.com\/blog\/pump-power-formula\/\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\">pump power formula guide<\/a>. This page stays on the other side of that relationship: known output and known input produce efficiency.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">Metric Pump Efficiency Worked Example<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_04.png\" alt=\"Metric Pump Efficiency Worked Example \u2014 BBP\" class=\"wp-image-6537\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_04.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_04-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_04-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_04-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_04-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n<p>Consider a water pump operating at 100 m\u00b3\/h and 30 m total dynamic head. The shaft measurement shows 13.0 kW.<\/p>\n<ol><li>Hydraulic output = 100 \u00d7 30 \u00f7 367 = 8.174 kW.<\/li><li>Pump efficiency = 8.174 \u00f7 13.0 = 0.6288.<\/li><li>Convert the decimal once: 0.6288 \u00d7 100% = <strong>62.9%<\/strong>.<\/li><\/ol>\r\n<p>If the measured electrical input is 14.5 kW instead, the wire-to-water efficiency is 8.174 \u00f7 14.5 \u00d7 100% = <strong>56.4%<\/strong>. Nothing happened to the hydraulic duty point. The percentage fell because the second boundary includes motor and drive losses.<\/p>\n<p>To <strong>calculate pump efficiency<\/strong> consistently, record flow rate, head, and input before doing the <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">pump efficiency calculation<\/a>. The result becomes useful for engineering and maintenance only when the operating condition is also recorded. Plants may monitor efficiency over time, but a lower value does not by itself identify wear: valve position, speed, liquid, and meter uncertainty can move the result. Compare like with like and look for a repeatable change larger than the measurement uncertainty.<\/p>\n<p>Peak efficiency is a curve property, not a guaranteed value at every operation. An efficient selection places the required duty near the relevant peak without violating NPSH, reliability, or control requirements. Positive-displacement equipment also needs its own performance method; do not transfer the centrifugal-pump shortcut blindly. The minimum documentation set is the measurement boundary, pump configuration, liquid, speed, instruments, and timestamp.<\/p>\n<div style=\"margin:24px 0; padding:16px 20px; background:#f5f5f5; border:1px solid #e0e0e0; border-left:3px solid #2d2d2d;\"><strong>\ud83d\udcd0 Rounding note<\/strong><p style=\"margin:8px 0 0;\">Keep unrounded intermediate values and round the final percentage to a precision supported by the measurements. Reporting 62.8774% from instruments that resolve only whole units creates false precision.<\/p><\/div>\r\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">US Customary Pump Efficiency Worked Example<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_05.png\" alt=\"US Customary Pump Efficiency Worked Example \u2014 BBP\" class=\"wp-image-6538\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_05.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_05-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_05-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_05-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_05-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n<p>The same approximate duty point converts to about 440 gpm and 98.4 ft. Suppose measured shaft input is 17.43 bhp.<\/p>\n<ol><li>Water horsepower = 440 \u00d7 98.4 \u00f7 3,960 = 10.93 hp.<\/li><li>Pump efficiency = 10.93 \u00f7 17.43 = 0.627.<\/li><li>Efficiency = <strong>62.7%<\/strong>.<\/li><\/ol>\r\n<p>The small difference from the metric result comes from rounded converted inputs. This avoids two common problems\u2014a rounding error and a unit mismatch\u2014when the original <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">measurement sheet<\/a> is retained and flow, head, and power are converted from one duty point. Do not treat the last decimal as a test discrepancy when the inputs were rounded first.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">The Input-Power Boundary Trace: Hydraulic, Volumetric, Mechanical, Motor, and Overall Efficiency<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_06.png\" alt=\"The Input-Power Boundary Trace: Hydraulic, Volumetric, Mechanical, Motor, and Overall Efficiency \u2014 BBP\" class=\"wp-image-6539\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_06.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_06-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_06-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_06-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_06-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n<p>The <strong>Input-Power Boundary Trace<\/strong> helps locate losses without pretending every efficiency term was measured independently.<\/p>\n<div style=\"margin:24px 0; overflow-x:auto;\"><table style=\"width:100%; border-collapse:collapse; border:1px solid #e0e0e0;\"><thead><tr style=\"background:#2d2d2d; color:#fff;\"><th scope=\"col\" style=\"padding:12px; text-align:left;\">Loss category<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">Where it appears<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">Evidence needed<\/th><\/tr><\/thead><tbody>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Hydraulic passage<\/td><td style=\"padding:12px;\">Flow separation, shock, recirculation, casing and impeller friction<\/td><td style=\"padding:12px;\">Validated hydraulic test or design model<\/td><\/tr>\r\n<tr style=\"background:#f5f5f5; border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Volumetric leakage<\/td><td style=\"padding:12px;\">Wear rings, balance paths, and internal clearances<\/td><td style=\"padding:12px;\">Leakage test or validated performance model<\/td><\/tr>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Bearing mechanical<\/td><td style=\"padding:12px;\">Radial and thrust bearings<\/td><td style=\"padding:12px;\">Torque or loss measurement<\/td><\/tr>\r\n<tr style=\"background:#f5f5f5; border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Seal mechanical<\/td><td style=\"padding:12px;\">Packing or mechanical seal faces<\/td><td style=\"padding:12px;\">Configuration-specific loss assessment<\/td><\/tr>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Disk friction<\/td><td style=\"padding:12px;\">Rotating impeller surfaces and balancing components<\/td><td style=\"padding:12px;\">Validated pump model<\/td><\/tr>\r\n<tr style=\"background:#f5f5f5; border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Motor electrical<\/td><td style=\"padding:12px;\">Copper, core, stray-load, and mechanical motor losses<\/td><td style=\"padding:12px;\">Motor input and shaft output at matched load<\/td><\/tr>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Drive conversion<\/td><td style=\"padding:12px;\">Variable-frequency drive power electronics<\/td><td style=\"padding:12px;\">Drive input and output power at matched load<\/td><\/tr>\r\n<tr style=\"background:#f5f5f5; border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Pump-only total<\/td><td style=\"padding:12px;\">All losses between shaft and liquid<\/td><td style=\"padding:12px;\">Hydraulic output and measured shaft input<\/td><\/tr>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Motor-and-pump total<\/td><td style=\"padding:12px;\">Motor plus pump losses<\/td><td style=\"padding:12px;\">Hydraulic output and motor electrical input<\/td><\/tr>\r\n<tr><td style=\"padding:12px;\">Wire-to-water total<\/td><td style=\"padding:12px;\">All included supply, drive, motor, and pump losses<\/td><td style=\"padding:12px;\">Hydraulic output and measured supply input<\/td><\/tr>\r\n<\/tbody><\/table><\/div>\r\n<p>You may estimate wire-to-water efficiency as motor efficiency \u00d7 pump efficiency, but only when both figures apply at the same load, speed, voltage, liquid, and operating point. Catalog peak motor efficiency multiplied by pump efficiency read at another flow is not a measured system result.<\/p>\n<p>This decomposition is diagnostic, not permission to invent component percentages. Pump-only overall efficiency can be measured directly even when hydraulic, volumetric efficiency, and mechanical efficiency are not separately known. Treat a multiplication of unverified sub-efficiencies as a model, label its inputs, and do not present it as an instrumented result.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">How to Measure Pump Efficiency in the Field<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_07.png\" alt=\"How to Measure Pump Efficiency in the Field \u2014 BBP\" class=\"wp-image-6540\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_07.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_07-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_07-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_07-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_07-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\r\n<ol><li>Define the boundary. Decide whether the denominator is shaft input, motor input, or supply input including a drive.<\/li><li>Stabilize the operating point. Record speed, valve position, liquid temperature, and system condition. Do not pair a flow reading from one minute with a power reading from another operating state.<\/li><li>Measure flow with an appropriate, installed, calibrated flowmeter and record its uncertainty.<\/li><li><strong>Determine total head.<\/strong> Use suction and discharge pressure or head, elevation, and velocity terms at defined measurement sections.<\/li><li><strong>Measure input power.<\/strong> Use a torque\/speed method for shaft power or a suitable analyzer for real electrical power.<\/li><li><strong>Repeat and compare.<\/strong> Take repeated readings, calculate uncertainty, then compare only with a curve or acceptance basis for the same configuration.<\/li><\/ol>\n<p>Flow measurement quality depends on meter technology, straight-run conditions, liquid properties, installation orientation, and calibration. Pressure instruments need appropriate range and elevation correction. Torque, speed, volume, temperature, and electrical power each carry uncertainty. Because efficiency is a quotient assembled from several measurements, a one-percentage-point change may not be meaningful when the combined uncertainty is larger.<\/p>\n<p>Formal test methods have application limits. The official <a href=\"https:\/\/www.iso.org\/standard\/41202.html\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">ISO 9906:2012 scope<\/a> is framed around acceptance testing with liquids that behave like clean, cold water. <a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/centrifugal-pumps\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">ASME PTC 8.2<\/a> states a Newtonian-viscosity liquid scope. Correct \u03c1gQH calculations for viscous or non-Newtonian process liquids do not automatically make a clean-water acceptance curve the right comparison.<\/p>\n<p>The US Department of Energy has also supported <a href=\"https:\/\/www.energy.gov\/cmei\/buildings\/articles\/wireless-sensor-pump-efficiency\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">sensor-based pump-efficiency measurement<\/a>. That illustrates why concurrent measurements matter; it does not certify any particular field sensor or replace calibration records.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">Read the Efficiency Curve and Find the Best Efficiency Point<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_08.png\" alt=\"Read the Efficiency Curve and Find the Best Efficiency Point \u2014 BBP\" class=\"wp-image-6541\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_08.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_08-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_08-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_08-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_08-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\r\n<p>The pump efficiency curve plots efficiency against flow at a stated speed, impeller diameter, and test condition. The best efficiency point (BEP) is the maximum of the relevant efficiency curve. The <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">Hydraulic Institute pump-curves reference<\/a> shows efficiency, input power, head, flow, and NPSH on the same performance framework.<\/p>\n<p>There is a subtle boundary issue: a bare-pump efficiency curve and an overall motor-and-pump efficiency curve need not peak at exactly the same flow. Current US regulatory definitions distinguish bare-pump and overall-efficiency concepts. Always identify which curve and denominator produced the stated BEP.<\/p>\n<p>Regulatory pump energy indices can combine prescribed load points and reference performance. They are not synonyms for the single-point percentage calculated on this page. The 2024 <a href=\"https:\/\/www.federalregister.gov\/documents\/2024\/05\/20\/2024-07873\/energy-conservation-program-energy-conservation-standards-for-circulator-pumps\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">US circulator-pump final rule<\/a> is one example of a broader rating framework. Apply it only to equipment inside its scope.<\/p>\n<p>If a field point appears inefficient, compare it with the curve for the same speed and impeller before diagnosing wear. Curves for another trim or liquid are weak evidence even when the flow is similar. Keep the curve revision and test configuration with the field record.<\/p>\n<p>If speed or impeller diameter changes, use the <a href=\"https:\/\/bbpmfg.com\/blog\/pump-affinity-laws\/\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\">pump affinity laws<\/a> as an estimate, then return to the applicable manufacturer curve. Affinity calculations often assume efficiency stays approximately constant; the actual efficiency curve decides whether that approximation is acceptable.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">The Efficiency Sanity Check: Diagnose Impossible or Misleading Results<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_09.png\" alt=\"The Efficiency Sanity Check: Diagnose Impossible or Misleading Results \u2014 BBP\" class=\"wp-image-6542\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_09.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_09-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_09-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_09-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_09-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\r\n<div style=\"margin:24px 0; overflow-x:auto;\"><table style=\"width:100%; border-collapse:collapse; border:1px solid #e0e0e0;\"><thead><tr style=\"background:#2d2d2d; color:#fff;\"><th scope=\"col\" style=\"padding:12px; text-align:left;\">Observed result<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">First checks<\/th><th scope=\"col\" style=\"padding:12px; text-align:left;\">Do not conclude yet<\/th><\/tr><\/thead><tbody>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Above 100%<\/td><td style=\"padding:12px;\">Unit conversion, head definition, density, input boundary, instrument scaling<\/td><td style=\"padding:12px;\">The pump has created energy<\/td><\/tr>\r\n<tr style=\"background:#f5f5f5; border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Unexpectedly low<\/td><td style=\"padding:12px;\">Operating point, wear, bypass flow, throttling, speed, power method<\/td><td style=\"padding:12px;\">The pump is defective<\/td><\/tr>\r\n<tr style=\"border-bottom:1px solid #e0e0e0;\"><td style=\"padding:12px;\">Readings wander<\/td><td style=\"padding:12px;\">Process stability, air, cavitation, meter location, sampling time<\/td><td style=\"padding:12px;\">A single average is representative<\/td><\/tr>\r\n<tr><td style=\"padding:12px;\">Curve mismatch<\/td><td style=\"padding:12px;\">Model, impeller trim, speed, liquid, test standard, BEP boundary<\/td><td style=\"padding:12px;\">The published curve is for the tested configuration<\/td><\/tr>\r\n<\/tbody><\/table><\/div>\r\n<p>An efficiency above 100% is not a high-performing pump; it is a data problem. The <strong>Efficiency Sanity Check<\/strong> starts with incompatible units and boundaries because they can produce a polished but physically impossible answer. It then checks whether all readings came from the same <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">operating point<\/a>.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">Frequently Asked Questions<\/h2>\r\n<h3 style=\"margin:28px 0 10px;\">What is the formula for pump efficiency?<\/h3><p>Pump efficiency is useful hydraulic output power divided by input power, multiplied by 100%. First calculate hydraulic output from density, gravity, flow, and total head. For pump-only efficiency, divide by measured shaft input. For wire-to-water efficiency, divide by measured electrical input for the complete boundary. The output and input must represent the same operating point.<\/p><p>Keep the efficiency as a decimal during the calculation and multiply by 100 only once at the end. If the resulting value exceeds 100%, check units, head, density, and power boundaries before interpreting it.<\/p>\n<h3 style=\"margin:28px 0 10px;\">How do you calculate overall pump efficiency?<\/h3><p>Define what \u201coverall\u201d includes. If it means the bare pump, divide hydraulic output by shaft input. If it means the motor-and-pump set or wire-to-water system, divide hydraulic output by measured electrical input. Multiplying motor and pump efficiencies is an estimate only when both efficiencies apply at the same load, speed, and duty point. Do not substitute the motor nameplate rating for measured input, and do not combine pump and motor values taken at different load, speed, or duty points.<\/p>\n<h3 style=\"margin:28px 0 10px;\">What is a good pump efficiency?<\/h3><p>There is no defensible universal percentage. Pump type, size, speed, impeller trim, liquid, and operating point all affect the result. Compare a measured value with the applicable manufacturer curve or acceptance criterion for that exact configuration. Generic industry percentages cannot replace a matched curve and a stated test boundary.<\/p>\n<h3 style=\"margin:28px 0 10px;\">Can pump efficiency be more than 100%?<\/h3><p>No. Any result above 100% means the calculated hydraulic output exceeds the selected input, which violates the energy balance. Check flow and head units, liquid density, gauge locations, instrument scaling, power factor, and whether the denominator is shaft or electrical power.<\/p>\n<h3 style=\"margin:28px 0 10px;\">How does BEP affect pump efficiency?<\/h3><p>Efficiency normally reaches its maximum near the best efficiency point of the applicable tested curve and falls as the duty point moves away. The exact shape is not necessarily symmetric. Also confirm whether the curve represents bare-pump efficiency or overall efficiency before comparing it with field data.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">What to Send BBP for a Duty-Point Review<\/h2>\n<figure style=\"margin:28px 0; text-align:center;\"><img decoding=\"async\" src=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_11.png\" alt=\"What to Send BBP for a Duty-Point Review \u2014 BBP\" class=\"wp-image-6543\" width=\"1200\" height=\"800\" loading=\"lazy\" style=\"max-width:100%; height:auto; border-radius:8px;\" srcset=\"https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_11.png 1200w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_11-300x200.png 300w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_11-1024x683.png 1024w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_11-768x512.png 768w, https:\/\/bbpmfg.com\/wp-content\/uploads\/2026\/08\/pump-efficiency-formula-h2_11-18x12.png 18w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/figure>\r\n<p>For a meaningful review, send flow, total dynamic head, liquid and temperature, density or specific gravity, frequency and speed, suction conditions, pump model, impeller diameter, and the method used to measure input power. Include the <a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\" target=\"_blank\" rel=\"noopener\">curve or test report<\/a> you are comparing against.<\/p>\n<p>Without these records, a low result cannot be separated reliably from a unit, boundary, or instrumentation problem. If repeated readings remain below the matched curve outside combined uncertainty, the next review can examine wear, bypass flow, speed, and operating position.<\/p>\n<p>BBP\u2019s <a href=\"https:\/\/bbpmfg.com\/centrifugal-pumps\/\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\">centrifugal pump range<\/a> includes end-suction and high-flow configurations. See the <a href=\"https:\/\/bbpmfg.com\/centrifugal-pumps\/end-suction-pump\/\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\">end suction pump<\/a> and <a href=\"https:\/\/bbpmfg.com\/centrifugal-pumps\/double-suction-pump\/\" style=\"text-decoration:underline; text-underline-offset:3px; color:#2d2d2d;\">double suction pump<\/a> pages for configuration context. Curve matching or test-report clarification can establish whether two efficiency figures are truly comparable; it should not be replaced by a generic promise.<\/p>\n<h2 style=\"margin:48px 0 16px; padding-bottom:10px; border-bottom:2px solid #2d2d2d;\">References &amp; Sources<\/h2>\n<ul>\r\n<li><a href=\"https:\/\/datatool.pumps.org\/pump-fundamentals\/pump-curves\" target=\"_blank\" rel=\"noopener\">Hydraulic Institute Data Tool: Pump Curves<\/a><\/li>\r\n<li><a href=\"https:\/\/www.energy.gov\/cmei\/buildings\/articles\/wireless-sensor-pump-efficiency\" target=\"_blank\" rel=\"noopener\">US Department of Energy: Wireless Sensor for Pump Efficiency<\/a><\/li>\r\n<li><a href=\"https:\/\/www.iso.org\/standard\/41202.html\" target=\"_blank\" rel=\"noopener\">ISO 9906:2012 scope<\/a><\/li>\r\n<li><a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/centrifugal-pumps\" target=\"_blank\" rel=\"noopener\">ASME PTC 8.2: Centrifugal Pumps<\/a><\/li>\r\n<li><a href=\"https:\/\/www.ecfr.gov\/current\/title-10\/chapter-II\/subchapter-D\/part-431\/subpart-Y\" target=\"_blank\" rel=\"noopener\">10 CFR Part 431 Subpart Y<\/a><\/li>\r\n<li><a href=\"https:\/\/www.federalregister.gov\/documents\/2024\/05\/20\/2024-07873\/energy-conservation-program-energy-conservation-standards-for-circulator-pumps\" target=\"_blank\" rel=\"noopener\">2024 Energy Conservation Standards for Circulator Pumps<\/a><\/li>\r\n<\/ul>\r\n<p style=\"margin-top:28px; color:#6b7280;\"><em>Formula examples are derived illustrations, not product acceptance-test results.<\/em><\/p>\n<\/div>\r\n","protected":false},"excerpt":{"rendered":"<p>The pump efficiency formula is useful hydraulic output power divided by input power, multiplied by 100%. The arithmetic is short. The important part is choosing the right input boundary: shaft power for the bare pump, or electrical power for the complete motor-and-pump system. This guide shows both methods, works the same duty point in metric [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":6533,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_gspb_post_css":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-6544","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bbp-blogs"],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":8}},"_links":{"self":[{"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/posts\/6544","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/comments?post=6544"}],"version-history":[{"count":0,"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/posts\/6544\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/media\/6533"}],"wp:attachment":[{"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/media?parent=6544"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/categories?post=6544"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bbpmfg.com\/ar\/wp-json\/wp\/v2\/tags?post=6544"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}