hp & watts

[Roo]

I admit I am thoroughly confused with hp and watts.

I have a Franklin 1hp submersible pump running on single phase 220vac. I use a dedicated 5k inverter to run it, it's only job. I find it very suitable for the task.

All calculations tell me that 1 hp = approx. 745 watts. However, the inverter tells me it's starting at 2,000 watts (this seems about right) and settling around 1,350 watts.

Why is actual consumption almost double that of specified consumption?

I need to sort this out as I want to upgrade to a 1.5 or 2 hp replacement. Anyone here with ideas for the discrepancy?

 

[Hedges]

There's watts and then there's VA. One subtracts current shoved back out of phase (from poor power factor) and the other is just Vrms x Arms.
That could be part of the issue. Could also be load. Motors can deliver over 100% of their rating.
If starting watts is really 2000W, I'd be surprised. For synchronous motors I expect 5x the nameplate rating for a couple tenth's of a second. I've measured it with an oscilloscope and current transformer.

If a 5kW inverter can start a 2 hp pump, then it probably has 10kW surge capability.