Pool Heater-Set At 84 or Turn Off After Use???

[Mendy48]

I have a gas heater that I often turn on the day I want to swim. My pool is often at 74 degrees and I like heating my pool to 84 degrees to swim (yup). The gas heater that I have brings the temperature up (in my pool) 1deg/hour. In other words, it will take 10 hours to bring to pool from 74 to 84 deg.

The questions is this: would it make sense to just set my heater to 84 deg and leave it there, as opposed to shutting the heater off and turning it back on to re-heat the pool. Someone told me .... coworker... that it will cost less to just set your gas heater at 84...because that will mean the gas heater isn't running 10 hours every-time you want to swim... I don't swim everyday so that's why I shut off the heater.

i.e., leaving the heater thermostat at a certain temp or turning it off then reheating the water for a full day

Any suggestions???

 

[ajw22]

I have a gas heater that I often turn on the day I want to swim. My pool is often at 74 degrees and I like heating my pool to 84 degrees to swim (yup). The gas heater that I have brings the temperature up (in my pool) 1deg/hour. In other words, it will take 10 hours to bring to pool from 74 to 84 deg.

The questions is this: would it make sense to just set my heater to 84 deg and leave it there, as opposed to shutting the heater off and turning it back on to re-heat the pool. Someone told me .... coworker... that it will cost less to just set your gas heater at 84...because that will mean the gas heater isn't running 10 hours every-time you want to swim... I don't swim everyday so that's why I shut off the heater.

Any suggestions???

No simple answer. It depends how often you do swim, how much temp your pool loses when the heater is off, and if the air temp is above or below the pool temp.

Let's say you heat up your pool to 84 on Sunday and the next time you plan to get into your pool is Thursday. And let's assume during the cold nights you lose 5 degrees each night. So the pool heater will have run for 20 hours between Sunday evening and Thursday to maintain 84 24 hours a day.

If you turn off the heater on Sunday evening and the pool temp drops to 74 by Wednesday night then it will take a 10 hour heater run to get it back to 84.

The pool temp will not drop below the night time air temp. Once you get warm night time temps then you can leave your pool heater on.

I like my pool at 86. My pool heater is set to run 9AM - 9PM. In May/June/Sept/Oct I turn the heater on in anticipation of swimming. In July & August with warmer nights I let the heater run every day. I lose a few degrees of pool temp over night and the heater gets it back by around noon. I do manually turn off the heater on days it is raining or gets exceptionally cold. No reason to waste the gas.

I do like my pool ready to swim when I want without waiting hours for it to heat up.

So the answer is ... it depends.

 

[Mendy48]

Right now.. in may... we don't swim that often... it's not as warm out as it should be to swim...we may swim once or twice a week. Your advise makes a lot of sense. Thanks for sharing.

No simple answer. It depends how often you do swim, how much temp your pool loses when the heater is off, and if the air temp is above or below the pool temp.

Let's say you heat up your pool to 84 on Sunday and the next time you plan to get into your pool is Thursday. And let's assume during the cold nights you lose 5 degrees each night. So the pool heater will have run for 20 hours between Sunday evening and Thursday to maintain 84 24 hours a day.

If you turn off the heater on Sunday evening and the pool temp drops to 74 by Wednesday night then it will take a 10 hour heater run to get it back to 84.

The pool temp will not drop below the night time air temp. Once you get warm night time temps then you can leave your pool heater on.

I like my pool at 86. My pool heater is set to run 9AM - 9PM. In May/June/Sept/Oct I turn the heater on in anticipation of swimming. In July & August with warmer nights I let the heater run every day. I lose a few degrees of pool temp over night and the heater gets it back by around noon. I do manually turn off the heater on days it is raining or gets exceptionally cold. No reason to waste the gas.

I do like my pool ready to swim when I want without waiting hours for it to heat up.

So the answer is ... it depends.

 

[Green Goblin]

Other factors to consider: whether you cover the pool or not, and if it's one time per week vs 2, would seem to make a big difference here.

At the extremes of these factors
If you're not covering the pool and you swim once per week-- my guess is that you probably spend less by heating it on the day you want to swim.

If you're covering it, and you swim twice per week, you may get closer to your coworker being right, still not sure if he would be right, but it would seem more possible.

Perhaps the best way to figure out would be try each strategy for a week and monitor your gas usage daily.

 

[Joshii]

There's no way keeping it at 84 would ever cost less. The greater the temp differential between pool and air, the faster you will lose heat. This is the same reason you set your thermostat in your house back when no one's home. It always costs less to re-heat to a certain temp than it does to maintain that temp consistently.

 

[ps0303]

If you leave the unit turned on and set to a temp, use a solar blanket on the pool to keep the heat in.

 

[Green Goblin]

Joshii, that would seem to be true if you are comparing like to like, but for pool owner behavior we aren't always comparing like to like. Someone maintaining a pool at 84 might cover it, while someone heating it up to 84 once per week might not.

Would it not be reasonable to suggest that if you raised a pool to 84, covered it and maintained it there for say 12 hours overnight, you might use less energy than raising the pool to 84, not covering it, and letting it cool down over night and reheating it again to 84 the very next day?

 

[Mendy48]

Yeah! I have a solar cover I use and I cover my pool when the pool is not in use; another reason why my co-worker suggested that I set the temp to 84 and leave it alone..don't shut the heater off. Mmmmmm. I was going to just try both ways and see how my bill comes out or monitor my gas bill...you're right, I should maybe do that.

Other factors to consider: whether you cover the pool or not, and if it's one time per week vs 2, would seem to make a big difference here.

At the extremes of these factors
If you're not covering the pool and you swim once per week-- my guess is that you probably spend less by heating it on the day you want to swim.

If you're covering it, and you swim twice per week, you may get closer to your coworker being right, still not sure if he would be right, but it would seem more possible.

Perhaps the best way to figure out would be try each strategy for a week and monitor your gas usage daily.

I figure that it wouldn't be the same since the pool is outside. I cover my pool when I set the temp at 84 and it remains covered until I swim in it. I just don't know if (since I have the cover on) I should really leave the heater on too...I guess I may not have to huh?

There's no way keeping it at 84 would ever cost less. The greater the temp differential between pool and air, the faster you will lose heat. This is the same reason you set your thermostat in your house back when no one's home. It always costs less to re-heat to a certain temp than it does to maintain that temp consistently.

Yeah! I have a solar cover for sure.

If you leave the unit turned on and set to a temp, use a solar blanket on the pool to keep the heat in.

I cover mine all the time with a solar cover.

Joshii, that would seem to be true if you are comparing like to like, but for pool owner behavior we aren't always comparing like to like. Someone maintaining a pool at 84 might cover it, while someone heating it up to 84 once per week might not.

Would it not be reasonable to suggest that if you raised a pool to 84, covered it and maintained it there for say 12 hours overnight, you might use less energy than raising the pool to 84, not covering it, and letting it cool down over night and reheating it again to 84 the very next day?

 

[Green Goblin]

Many people heat their pool with the cover on-- I think, at least.... that's how I did it when I had a pool.

Watching your gas bill may not really be the best way to do it. Generally a gas bill is done at most monthly, so you'd have to do a month one way, and then a month the other way, and seeing as it's summer, it won't really be fair because the weather is getting hotter anyway.

Monitoring your gas consumption by looking at your meter over a shorter period of time with hopefully more uniform temperatures (even that isn't for certain) would seem to be the way to go.

What Joshii says seems likely to be true in most instances.

 

[PoolGate]

As long as you are willing to wait for the pool to heat, it is cheaper to turn off the heater when you aren't using the pool. BTUs are BTUs. The pool needs a certain amount to heat to a certain temp and will lose a certain amount. For me, my heater has 2 set points. I used the low, set at 85, for when I am not using the pool. When I want to use it, I activate the high set point, which is set at 88. I swim at least 3-4 times/week so I don't want to wait for the pool to heat up more than a couple hours. Also once summer hits, it will take almost nothing to maintain the pool at 88+. The heater will barely ever cycle on at that point. My gas and electric bills are on the budget equalizing plan so no matter how much I use, I never really see much of a change in my bill. The trade-off is that instead of seeing almost nothing on months I don't need gas, my gas bill is around $200 every month.

 

[Mendy48]

Thanks for the advise PoolGate.... All I'm worried about is my gas bill... LOL... I'm very worried. I haven't received it yet, but I'm keeping my fingers crossed for sure. Thanks again.

As long as you are willing to wait for the pool to heat, it is cheaper to turn off the heater when you aren't using the pool. BTUs are BTUs. The pool needs a certain amount to heat to a certain temp and will lose a certain amount. For me, my heater has 2 set points. I used the low, set at 85, for when I am not using the pool. When I want to use it, I activate the high set point, which is set at 88. I swim at least 3-4 times/week so I don't want to wait for the pool to heat up more than a couple hours. Also once summer hits, it will take almost nothing to maintain the pool at 88+. The heater will barely ever cycle on at that point. My gas and electric bills are on the budget equalizing plan so no matter how much I use, I never really see much of a change in my bill. The trade-off is that instead of seeing almost nothing on months I don't need gas, my gas bill is around $200 every month.

 

[Joshii]

Thanks for the advise PoolGate.... All I'm worried about is my gas bill... LOL... I'm very worried.

It will probably cost around $40 to heat your pool 10 degrees, each time you do that. Heating a pool off-season is wicked expensive :/