Combine measured flow, suction/discharge pressure, gauge elevation, specific gravity, and electrical input into a pump performance screen.
Why it matters: A defensible field comparison requires synchronized measurements, correct gauge references, fluid properties, and a visible scheduled point.
ΣCALCULATE · VERIFY · INTERPRET
Calculated result
Engineering evaluation
Calculation complete—verify project criteria
Measured pump head (H)74.3 ft
Hydraulic output power (Pʰ)
1.399 kW
Hydraulic output power (Pʰ,ʰᵖ)
1.876 hp
Wire-to-water efficiency (η)
69.956 %
Flow relative to schedule (Q%)
100 %
Head relative to schedule (H%)
99.067 %
Engineering interpretation
The measured point yields 74.3 ft head, 1.399129 kW hydraulic output, 69.95644% wire-to-water efficiency, 100% scheduled flow, and 99.06667% scheduled head.
Important limitations
No hidden flow, head, or efficiency tolerance is applied. Confirm gauge locations and elevations, velocity-head treatment, instrument calibration, synchronized stability, electrical boundary, fluid properties, pump/system curves, minimum flow, uncertainty, and user-approved acceptance criteria.
Motor-driven equipment
Estimate electrical demand and energy use
Use nameplate information and an operating schedule to screen motor input power, current, annual energy, and operating cost. Results update automatically.
Optional companion calculation
Choose the motor nameplate output-power convention.
Rated shaft output, not electrical input.
Used to estimate current; it does not change the hp-based energy result.
Use efficiency at the evaluated load point when available.
Use measured or defensible operating load rather than motor nameplate size alone.
Used only for the estimated current calculation.
Assumes all selected motors operate concurrently at the entered load.
Replace the profile with the actual occupied, process, or control schedule.
$/kWh
Use the applicable marginal utility energy charge; demand charges are not included.
Estimated result
Total motor input power (Pin,total)6.21 kW
Current per motor (I)
9.18 A
Total coincident current (Itotal)
9.18 A
Daily energy (Ed)
50 kWh/day
Annual operating hours (Hy)
2,080 h/year
Annual energy (Ey)
12,925 kWh/year
Annual energy cost (Cy)
$1,551/year
Equations and assumptions
Nameplate-based screening method
Horsepower is converted using 1 hp = 0.7457 kW. This estimate assumes steady average load and the entered operating-point efficiency. Voltage and power factor affect estimated current, but hp, load, efficiency, quantity, and schedule establish the energy estimate. VFD speed profiles, cycling, standby power, demand charges, and process variation require separate evaluation.
Pʰ=0.745699872Pʰ,ʰᵖ (I-P) or 998SG·9.80665QH/1000 (SI)
η=100Pʰ/Pᵉ
Q%=100Q/Qᵈ
H%=100H/Hᵈ
Current substitution
H=74.3 ft from Pᵈ=35, Pˢ=5, SG=1, Δzᵍ=5; Pʰ=1.399129 kW=1.876263 hp; η=69.95644%; Q%=100%; H%=99.06667%; Pᵉ=2, Qᵈ=100, Hᵈ=75.
Calculation sequence
Step-by-step method
Calculate pump head from pressure differential, specific gravity, and signed gauge elevation difference.
Calculate hydraulic output power and wire-to-water efficiency.
Compare flow and head only with the visible user-entered scheduled point.
Equation legend
Inputs and calculated quantities
Q
Measured flow — gpm or m³/s
Pˢ
Suction pressure — psi or kPa
Pᵈ
Discharge pressure — psi or kPa
Δzᵍ
Discharge-minus-suction gauge elevation — ft or m
SG
Fluid specific gravity — dimensionless
Pᵉ
Measured electrical input power — kW
Qᵈ
Scheduled flow — gpm or m³/s
Hᵈ
Scheduled head — ft or m
H
Measured pump head — ft
Pʰ
Hydraulic output power — kW
Pʰ,ʰᵖ
Hydraulic output power — hp
η
Wire-to-water efficiency — %
Q%
Flow relative to schedule — %
H%
Head relative to schedule — %
Applications
How this calculation is used
Building design
Document the scheduled flow and head basis.
Construction
Check gauge, power, and flow measurement boundaries.
Commissioning
Calculate measured head, hydraulic power, wire-to-water efficiency, and percentages of user-entered scheduled values.
Quality controls
Assumptions and limitations
Assumptions
Entered values describe one documented system and use a consistent unit, energy, pressure, elevation, and measurement basis.
Measurements are representative and synchronized where the calculation combines field readings.
Limitations
Velocity-head differences are omitted unless separately represented; the screen does not select a pump, establish minimum flow, or replace the manufacturer curve and system curve.
No hidden flow, head, or efficiency tolerance is applied. Gauge locations, test stability, input-power boundary, fluid properties, uncertainty, and acceptance criteria require Frank/manufacturer review.
Field use
Verification procedure
Confirm the calculation boundary, source documents, formula symbols, and units.
Record representative field values or approved project inputs and their sources.
Review the result against the applicable code, criteria, manufacturer data, and measurement uncertainty.
Common engineering mistakes
Combining values from different system boundaries, operating periods, temperature bases, or unit conventions.
Treating a calculated screening value as a hidden pass/fail threshold or final design decision.
Technical basis
References and source standards
Hydraulic InstitutePump-system, test-boundary, and manufacturer-curve context; exact equipment data remain controlling.
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
