Before I converted, I used to get estimated power at a variety of speeds for my boat, and I looked at two other electric boats for which I had actual data (3 points for one boat and just one for the other). In those cases, the real life boats used 2-3 times less power than the calculator predicted. I applied that factor to the estimated power for my boat, and later took note of the power it really consumed at various speeds. I found the adjusted estimate to be quite good, though the actual was more impacted by speed than the estimate.
