I need a pool heater!

[chem geek]

Just so you are aware, heating the pool with a gas heater is very, very expensive. We have a solar system to keep our pool at 88F (it's used for swim therapy for my wife, and I happen to like warmer water too) as much as possible and we use gas to assist in this, especially at the start and end of the season. Even so, we only are able to swim from around mid-April to mid-November and we live in a temperate climate (near San Francisco) that only sometimes gets to freezing (typical winter overnight temperatures are in the 40's). Part of the problem isn't the pool water temperature, but how cold the air temperature is outside, especially when wet. It's not like a spa where it is so warm that your body is able to bear the cold air briefly.

If you do plan to heat your pool with gas, then you should invest in a highly efficient insulated pool cover. We have an electric opaque cover that is not insulated (though it is convenient) and though it cuts down heat loss by about half, that still means we lose 3-4F overnight (instead of 6-8F) and a little less through a cold day. With an insulated cover, you could cut the loss in half again.

When comparing heaters, look at the output rating in BTUs. Every 100,000 BTUs will heat 10,000 gallons of water by 1.2F degrees every hour. However, remember that your pool will be losing heat rapidly if it is a lot warmer than the surrounding air and ground. The cost of a gas heater can be determined by it's input BTU/hr. rate which you divide by 100,000 to get Therms/hour. Natural gas costs about $1.39/Therm where I live. The bottom line is that you could easily spend $400 or more heating your pool for a month.

Richard