is pool heater worth it if you are not going to cover at night?

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archer636

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Jul 6, 2016
158
Gainesville, FL
I only use the pool about 6 months a year, and I would like the water to be a few degrees warmer during those months. I am thinking of solar heater. Pool is not screened- however there are a lot of trees around.
I will not be covering the pool at night. Manual covers are just too much work everyday (I have tried). Auto covers are outside my budget.
Question is, will I see any noticeable difference in temperature if I don't cover?
surface area is 720 sq ft. Budget for solar heater is about 5k
 
The pool will definitely be warmer than without the solar heating, but it's not possible to say by how much. If you add 75% to 100% of the surface area of the pool, it usually works very well. Without a cover, you won't be able to extend the swim season very much, but you'll have warmer water to swim in, especially on sunny days. My system has 60% coverage, and I only use my cover in spring to get the pool up to temperature, 4-6 weeks seems to work pretty well.
 
Without a solar cover to retain the heat overnight, you'll probably want to operate in "spot heating" mode where you warm the pool up for when you plan to be in it. If you have NG or propane available, those large pool heaters can get you heat when you need it within a few hours or so of heating. You'll lose all the heat you added but you can at least time it to when you'll most likely be swimming.

With solar panels and electric heat pumps, you really can't spot heat with those as they are too slow. With solar, you only get heat when the sun is out so you'll have to run it as soon as the sun is up and keep it going. You might get a few degrees from it but not that much.

I totally understand about pool covers, my pool is uncovered all the time because covers are just too much work. But, I have a 400 kBTU/hr gas heater so, in the spring, when the pool is cool and I know the kids want to swim, I just set the automation to run it a few hours before I know they'll be swimming and we get warmer water. It's a bummer knowing that the heat will just dissipate overnight, but at least the kids have fun.
 
You're not far from me and I don't use my cover from say mid April to mid October, but my pool is much smaller. I bought 280 Sq ft solar for my pool which is about 400 sq ft so 70%. My pool is screened (southern with some trees and covered patio taking part of the sun) my roof and solar gets pretty good southern exposure. I spent just over 4K (which probably wasn't a great price) but I'm very happy with the temps. The average is probably low of 80 high 90 on the fringe months, in the summer I turn the solar off when it hits 90. With a pool 3x larger (and if deeper it's hard to tell if you will get the same benefit) I run my solar/pump from 10-4 in winter, to 9-6 in the fringe months and maybe 9-noon in the summer.

I do use the cover all winter from mid oct to mid apr and today I was swimming in a 90 degree pool
 
JoyfulNoise said:
Without a solar cover to retain the heat overnight, you'll probably want to operate in "spot heating" mode where you warm the pool up for when you plan to be in it. If you have NG or propane available, those large pool heaters can get you heat when you need it within a few hours or so of heating. You'll lose all the heat you added but you can at least time it to when you'll most likely be swimming.

With solar panels and electric heat pumps, you really can't spot heat with those as they are too slow. With solar, you only get heat when the sun is out so you'll have to run it as soon as the sun is up and keep it going. You might get a few degrees from it but not that much.

I totally understand about pool covers, my pool is uncovered all the time because covers are just too much work. But, I have a 400 kBTU/hr gas heater so, in the spring, when the pool is cool and I know the kids want to swim, I just set the automation to run it a few hours before I know they'll be swimming and we get warmer water. It's a bummer knowing that the heat will just dissipate overnight, but at least the kids have fun.
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that makes sense- since I use it only on weekends anyways. My only concern is the cost of gas to heat 28kgal water... is there a semi-accurate way to calculate cost per degree per gallon?
 
archer636 said:
that makes sense- since I use it only on weekends anyways. My only concern is the cost of gas to heat 28kgal water... is there a semi-accurate way to calculate cost per degree per gallon?
Click to expand...

Assume that a gas heater is about 85% efficient. 1 BTU raises the temperature of 1 pound of water 1 degree F. 1 therm (~ 100 cu ft of nat gas) is approximately 100,000 BTU.

So, if you know your NG cost in $/therm, you can get a rough estimate of the amount of gas you’ll need/use.
 
JoyfulNoise said:
Assume that a gas heater is about 85% efficient. 1 BTU raises the temperature of 1 pound of water 1 degree F. 1 therm (~ 100 cu ft of nat gas) is approximately 100,000 BTU.

So, if you know your NG cost in $/therm, you can get a rough estimate of the amount of gas you’ll need/use.
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It comes to about $2 and 30 minutes per degree(400 kbtu) so a 10 deg. rise is gonna take about 5 hours and $20 for a weekend... not bad!
Only issue is the meter is on the other side of the house so running a line is probably gonna cost a good bit.
 
archer636 said:
It comes to about $2 and 30 minutes per degree(400 kbtu) so a 10 deg. rise is gonna take about 5 hours and $20 for a weekend... not bad!
Only issue is the meter is on the other side of the house so running a line is probably gonna cost a good bit.
Click to expand...

Yeah, that’s only the heat input. You also have to account for evaporative heat loss if the water temp is greater than the air temp. The site Marty linked to can give you a better estimate of cost.

Your meter will likely need upgrading (many utilities charge for that) and a gas line can easily cost $11-$15 per linear foot to run. Long runs require larger diameter gas pipe (mine is 2” because thevrun is over 150’ long) and that adds to it.

I thought you might have gas already there.
 

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If you wander over to this post from mas985...
Hydraulics 101 - Have you lost your head?

You can click "Excel" at the end of this paragraph in post #3. Very cool tool! (warm too). A bit of a browse there gives you an appreciation for all the forms of heat loss and gain.
"Pool Heat Transfer Tools* - Estimates heat loss and gain from a full heat transfer model that includes the effects of the sun, solar panels, NG heater, heat pump, and environmental conditions. It will also estimate the amount of water lost per day/week due to evaporation. Included are tabs to estimate heat loss from pipes and how long it can take for a pipe to freeze. New cross-platform version: Excel"
 
JoyfulNoise said:
Yeah, that’s only the heat input. You also have to account for evaporative heat loss if the water temp is greater than the air temp. The site Marty linked to can give you a better estimate of cost.

Your meter will likely need upgrading (many utilities charge for that) and a gas line can easily cost $11-$15 per linear foot to run. Long runs require larger diameter gas pipe (mine is 2” because thevrun is over 150’ long) and that adds to it.

I thought you might have gas already there.
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how about heat pump? the marketing material for pentair claims over twice as many BTUs per dollar- though it would take about 4 times longer.

https://pentairpool.com/~/media/websites/pool/downloads/heaters%20and%20heat%20pumps/brochures/ultratemp_high_performance_heat_pump_br_english.pdf
 
archer636 said:
It comes to about $2 and 30 minutes per degree(400 kbtu) so a 10 deg. rise is gonna take about 5 hours and $20 for a weekend... not bad!
Only issue is the meter is on the other side of the house so running a line is probably gonna cost a good bit.
Click to expand...

That is about right I calculated my 400k BTU NG heater costs around $4/hour to run. I get 1-2 degrees/hour in my 29k gallon pool. I did not see anything out of the ordinary on my gas bill since I am on the gas cost equalizing plan. So even if it costs you $100/month more, that'll be spread out over the year so if you are not on that maybe look into it I think most utilities offer it.

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archer636 said:
how about heat pump? the marketing material for pentair claims over twice as many BTUs per dollar- though it would take about 4 times longer.

https://pentairpool.com/~/media/websites/pool/downloads/heaters%20and%20heat%20pumps/brochures/ultratemp_high_performance_heat_pump_br_english.pdf
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More like 24x longer. 1 degree/day compared to 1 degree/hour. In lower temps the heatpump will not be able to keep up with the nightly loss either. Heat pump owners are generally happy but operating cost are really the only reason to get a heat pump. The unit itself is also typically almost 2x as much. If you do go heat pump you really need to get the solar cover. You will also lose out on that nice 10 degree warmer water coming out of your returns. For us our waterfalls also pour out hot water! It is REALLY nice!
 
PoolGate said:
More like 24x longer. 1 degree/day compared to 1 degree/hour.
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not sure that's accurate- remember I live in Florida! at an ambient temp of 80, Pentair 140 heatpump is supposed to output 135kBTU/hr vs 328kBTU/hr for 85% gas furnace.

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needsajet said:
If you wander over to this post from mas985...
Hydraulics 101 - Have you lost your head?

You can click "Excel" at the end of this paragraph in post #3. Very cool tool! (warm too). A bit of a browse there gives you an appreciation for all the forms of heat loss and gain.
"Pool Heat Transfer Tools* - Estimates heat loss and gain from a full heat transfer model that includes the effects of the sun, solar panels, NG heater, heat pump, and environmental conditions. It will also estimate the amount of water lost per day/week due to evaporation. Included are tabs to estimate heat loss from pipes and how long it can take for a pipe to freeze. New cross-platform version: Excel"
Click to expand...

very nice excel file. The Heat Txfr sheet is way over my electrical engineer head- the heater page is nice though.
 
Our 125k btu heat pump raises our 10k gal pool 1deg/hr. I’m very impressed with its capability here in FL. We don’t cover the pool, and generally lose 1-2 deg overnight. We decided against solar as we wanted to have control over pool temp so we could plan for weekends and visiting friends etc. I find it very economical to run. Mind you it was the only option, we don’t have natural gas and propane doesn’t make sense.
 
I would look into an AC heat recovery option (like in my sig) if you are looking at solar. Ideal for Florida where you are air conditioning your house most of the time. I have an uncovered pool in MA and it keeps my pool 5 or more degrees hotter than it normally would without a heater.
 
archer636 said:
it's a tempting concept. Sounds like the jury is still out:

Hotspot FPH AC heat reclamation pool heater - a review! - Page 5
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That's my thread. I started it specifically because when I was looking at this as a heating option, all l I had to go on were people's hypotheticals on how it "may" work, from people who didn't own one. So I took a chance and had it installed and I love it. So do others who actually have one. I started the thread so others could hear from an actual customer, rather than having to rely on hypothetical performance numbers.
 
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