Hydraulic Power Unit Calculator

The calculator divides required hydraulic HP by pump efficiency to get the exact motor HP needed, then rounds that up to the nearest standard NEMA frame size from a fixed list (0.5, 0.75, 1, 1.5, 2, 3, 5, 7.5 HP, and so on). Because the list has gaps that widen at larger sizes, a calculated requirement of, say, 21 HP jumps to a 25 HP frame — the gap you see is simply the distance to the next size actually sold, not a built-in safety margin.

Reservoir size is computed as required GPM × reservoir multiplier, then rounded up to a standard tank size. The default multiplier of 3× reflects a traditional industrial rule of thumb that gives fluid enough dwell time to release entrained air and shed heat; dropping to 2× or 1× (typical for compact or mobile equipment) directly and proportionally shrinks the recommended tank, so it's worth setting deliberately rather than leaving at the default.

That figure and the 2,000 hours/year duty assumption are placeholders meant to give a ballpark cost, computed as motor kW × 2,000 hrs × duty cycle × $0.12. Your actual electricity rate and annual runtime will differ, so the dollar figure should be treated as a rough order-of-magnitude number to recalculate manually with your real utility rate and expected operating hours.

Hydraulic HP is the useful power delivered to the circuit, computed directly from PSI × GPM / 1714. Required motor HP is larger — it's hydraulic HP divided by pump efficiency, accounting for the power lost to internal pump inefficiency before it ever reaches the fluid. The gap between the two is exactly the source of the heat-generation estimate elsewhere in the results.

No — it's collected for your reference, but the sizing calculations above are driven entirely by the Required flow (GPM) figure you enter, which is meant to already represent the total simultaneous demand from all actuators.