HP Calculations

In reply to a comment here, I realised I hadn't shown my workings!

So is the 12hp engine powerful enough?

This would be the maximum output.  It's very unlikely my batteries could ever draw this much. The plan is to run the engine at 1500rpm, however it can be run faster if needed.  Why 1500?  well its very quiet at that rpm, but even at 2000rpm its a fraction of the noise at 3000rpm.

This is the horsepower required to achieve this.

This is what I am looking to achieve at 1500rpm

This is the horsepower required.

These calculations are of course in ideal situations with a new engine, however there is still about 33% to play with.

So time will tell, but I'm confident the engine will drive it.  Interestingly when I was considering a 1500rpm 4 pole 230v alternator it was calculated by the intended supplier that it could not exceed 3kw output.