Depends on the pump and your local rates. It should tell you the watts per hour somewhere on the pump. Look on an old bill and find out the KW/hour rate. usually anywhere from $0.08 up to $0.20 per KW hour depending on your area and useage.

Good question orcuttnyc. I have been researching this myself as I'll soon be installing a solar PV system to generate all our household electricity. This is an expensive exercise so reducing our electricity consumption has become a priority.

It pays to shop around because wattage varies widely amongst pumps of similar pumping capacity and head. I was looking for a submersible pump that would turnover around 3000GPH at a 1m head. I found that between different makes and models power consumption varied from 100 to over 1000 watts! Where I live that translates to annual running costs of approx $100 - $1000 per year (assuming you run the pump 24/7).

I found that amongst submersible pumps, European models such as Oase and Laguna tended to have the lowest running costs.