Pump and Fan Speed Energy Calculator
Estimate relative pump or fan flow, head, and shaft power at a changed speed using the ideal affinity laws.
Enter a matching operating point
Ideal affinity-law estimate
About this calculator
Enter one pump or fan operating point and a target speed to estimate relative flow, head, and shaft power. It is intended for preliminary comparison of speed changes.
Confirm the expected operating point against the system curve and equipment documentation before using the estimate for an application decision.
Method and assumptions
For geometrically similar operation, the ideal affinity-law ratios are flow ∝ speed, head ∝ speed², and shaft power ∝ speed³. The calculator applies those ratios to the entered base values.
This simplified model does not solve a pump or fan curve against a system curve. Static head, efficiency changes, minimum flow, motor cooling, vibration, cavitation, and control limits are not modeled.
FAQs
What base values should I enter?
Use flow, head, and shaft power that describe the same measured or documented operating point at the entered base speed.
Does this predict the actual flow in my system?
No. It is a screening estimate. Static head, the system curve, control method, efficiency changes, and equipment limits can materially change the actual result.
Sources
Verify affinity-law use, operating curves, and allowable speed range against the pump or fan manufacturer’s engineering documentation.