Quick question: Efficient use of heater...

[dcastine]

I have a 20,000 gallon Gunite pool in the Boston area, I have a 250,000 BTU Pentair NG heater - works great. My pool filter/heater are running 9am-9pm. Would it be more cost effective to keep my heater ON set a certain temp rather than firing the thing up in the AM to get the pool up to temperature?

We use a solar cover at night and lose very little temp (weather permitting).

On the rainy/cloudy days I would of course turn the heater off...

Thanks
Dave

[mas985]

Heat loss increases with increasing water temperature so to minimize heat loss and thus cost, you would only want to heat the pool when you use it. Unfortunately, that is not always practical because it takes time to heat the pool. If you are using the pool nearly every day then you are probably doing the right thing by heating during the day since heat loss tends to increase during the night due to dropping dew points and temperatures but since you are using a cover and don't lose much heat it probably doesn't matter much either way.

[Poconos]

The simple answer is to use the heater only when you need the water warm. From a thermal standpoint, heat transfer is proportional to temperature difference and in this case, water and air. Stated another way, you lose less heat if you allow the water to cool down and get closer to air temperature than keeping the water well above air temp. This ignores the convenience factor of being able to jump into comfortable water at any time. If you don't use the pool for several days then by all means shut down the heater and save $$$.
Al
Edit: Looks like Mark and I were typing at the same time. Same ideas.