CHART - Saving from using a Cover if heating your pool

[Spensar]

The links below are for nice charts from the U.S. Department of Energy - Energy Efficiency and Renewable Energy: A Consumer's Guide to Energy Efficiency and Renewable Energy

The tables estimate annual costs by location, by water temperature, and with or without using a pool cover. Assumptions are made on the size of pool, heater efficiency, and pool size, and energy cost of course. Given the constant variables, it's the ratio between the cost of cover and no cover that is eye-popping.

Natural Gas
http://www.eere.energy.gov/consumer/.../mytopic=13180

Heat Pump
http://www.eere.energy.gov/consumer/.../mytopic=13220


There is also a good blurb on pool covers t http://www.eere.energy.gov/consumer/.../mytopic=13140

Since a cover reduces evaporation, this statement about a pool cover makes sense: "Conserve water by reducing the amount of make-up water needed by 30%–50%: