Gas heater vs. Heat pump

newgarage

Member
Jul 5, 2010
12
New York
New inground pool install almost complete. Vinyl lined concrete wall hard bottom 20x40 3 1/2'-8' depth on long island , NY.
I have a southern exposure in a sunny yard . All of my pool equipment is about 30' from the electric and natural gas line in my garage, so either energy source is an option. I'm trying to decide if I should go with a gas heater or electric heat pump to extend the pool season. I've gotten mixed opinions from
people I know that have pool heaters. LIPA costs are 19 cents per kwh and nartional grid natural gas costs are about 80 cents per therm(100k btu).
How do figure out cost of operation?
 

lightly

Member
Aug 9, 2010
6
Long Island, NY
I am in Long Island too and my neighbor and I had identical 20'x40' pools built at the same time. He had a gas heater installed I opted for a heat pump. I didn't want to go through the hastle of running the gas line and having keyspan install a larger gas meter.

After 4 years of running my heat pump I definitely wished I had installed the gas heater!!! The main reason is convenience. After this week's rains my pool temp dropped from 82 to 74. I now have to run the heatpump (and of course the pump) for two days straight (24hrs/day) to get the temp back up to 82 so my wife will swim this weekend. After running it since yesterday morning the pool temp went from 74 to 79......my neighbor will just turn his heater on for a few hours on Saturday morning and get his water up to 82 in!!

Also forget about what the sales people & brochures tell you about efficiencies vs. ambient temp. Don't expect the heat pump to extend your swim season here on LI. It does not raise the pool temp very well when it's cool outside say in the 60's. Again I run my heatpump all day and night and I'm lucky if I can raise the pool temp by a degree a day. On cool nights the pool actually drops in temp. Again my neighbor turns on his heater a few hours before swimming and he's in the pool.

I never did the math on the actual cost comparison of use but I have to believe the heatpump is all that cheap when I have to run the whole system 24/7 to actually warm the water (and that's only when the air temp is in the high 70's to 80's)

Go with the Gas heater!!!

Hope this helps.
 

kenmar

LifeTime Supporter
Apr 13, 2009
288
Schnecksville, PA
I have a gas heater and my experience is similiar to "Lightly's" neighbor.
On average, I can increase my pool temp by about 1deg per hour
 

mamasproject

Well-known member
Oct 8, 2009
97
I vote for the gas heater too! The heat pump will cost you $2000 more than the gas heater! If you only use the pool on weekends or a day here or there why would you want to waste all that energy heating a pool nobody is using????
Our pool heater raises our pool 2 degrees per hour and uses 4 gallons of propane per hour. We have turned it on a total of 4 times this year!
 

tim_pool_newbie

Bronze Supporter
LifeTime Supporter
Oct 6, 2009
164
I have no knowledge or experience with heat pumps, but I can tell you a bit about my natural gas heater that I just had installed with my new IGP. It's a 39,9k BTU heater and just like the other responses you received, I can tell you that I can turn the heater on and in just a very short period of time (an hour or so), raise my temperature quite a bit. I mostly have only weekend bathers, so I leave the heater off all week long here in Northeast PA and just turn it on right before my guests arrive. I actually like my water on the HOT side (85-88) and I have no problem getting it up to that temperature in a very short period of time.

If you're looking to compare this on a financial basis, I can tell you that my gas bill is not that bad either. I have natural gas for cooking and heating inside the house as well, and my bill for June was about $160 while my bill for July was only $76. That was 123 CCFs and 54 CCFs respectively. Hope you can use those numbers to calculate your gas costs in your area.

I vote Gas Heater!!
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
mamasproject said:
I vote for the gas heater too! The heat pump will cost you $2000 more than the gas heater! If you only use the pool on weekends or a day here or there why would you want to waste all that energy heating a pool nobody is using????
Our pool heater raises our pool 2 degrees per hour and uses 4 gallons of propane per hour. We have turned it on a total of 4 times this year!
Using your example, an 8 degree rise will take 4 hours and $44 worth of propane. A typical heat pump this time of year will put out ~60,000 BTU an hour. On a 20,000 gallon pool, it would take ~22 hours to raise it 8 degrees. At $0.15 per kW/hr (your may be more or less, $0.15 is what mine is with taxes, transmission, etc), you will spend ~$6.60 to run it. Add another 8 hours of pump run time and the total cost is maybe $7.00. Thats ~7 times cheaper. You could run the HP and filter pump 24/7 for a month to maintain the pool temp for ~$220 per month. That same $220 will run a gas heater maybe 18-20 hours total.



Now, that being said, the rains we got last week (we got the same soakers here in massachusetts) really reduce the output of a heat pump. All that cold rain really disapates the heat from the heat exchanger and reduces the BTU put into the pool, I'll grant you. When the cool weather and rain started on sunday, my pool was at 85 degrees. On monday morning, even with the solar cover, it went to 79. My heat pump ran 12 hours a day (7 am to 7 pm) from monday morning to yesterday, so 4 days basically. At the end of each day, the temp of the pool was 83 degrees. It did take 12 hours to put in about 4 degrees a day to maintain it. Thats 12 hours for 4 days so that 48 hours of run time. So over that 4 days, that's ~$20 to keep it running for 12 hr/day for 4 days. If I did'nt heat it for those 4 days at all, and let it get down to 72 (which is where i figure it would have been) that would be 11 degrees to get it back to 83. With LP, it would take 4 hours and 16 gallons (~$44) to heat the pool (LP in my area is $2.75/gallon. Much faster, but still double the price.

Now, that all said, sometimes I'm frustrated too with the speed that a heat pump works, and the fact on rainy days the BTU output is really, really low. I do wish the heat pump industry would put out realistic numbers for BTU output. It's difficult since ambient conditions can change it pretty drastically. But, the COP numbers that are based on 80 degree ambient temp and 80% humidity are not realistic. I've even considered adding a 250,000 BTU LP heater as a supplement for my HP when I get frustrated, but when I run the numbers, it still doesnt make sense as much as you might think it does.

Tim, natural gas is another animal all together. A NG heater is much cheaper to run that a LP heater. For comparison, a gallon of propane is about equal to a therm of NG in terms of BTU output (~100,000). The average cost of a therm of NG is $1.00 (mine is $0.77) and the average cost of LP is $3.00 (mine is $2.75). So, a 400,000 BTU NG heater costs about $4.00 per hour to run and a 400,000 BTU LP heater costs $11 dollars to run; almost 3 times. A Heat pump cost about $0.55, but puts out less BTU per hour.

As mentioned above, you also need to take into account how you use the pool. if you use it only on weekends, maybe gas is the way to go. We use ours 4-5 days a week, sometimes everyday. For me, LP doesnt make much sense. Electric rates are cheap too. If you live in cali where they are $0.40 /kW/hr, then gas might make more sense. In the end, gas vs HP depends on a number of factors.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,423
Pleasanton, CA
Someone else just asked this same question here.

For which I responded:

Which one wins out depends on how much you pay for gas vs electricity. If your gas rate ($/therm) is 4.7x more than the electrical rate ($/kwh), the heat pump will win out. Less than that, the gas heater will cost less. Here are the numbers:

80% efficient gas heater ~ 80,000 BTU/hr/Therm
5.0 COP Heat Pump ~ 17,000 BTU/hr/kwh

But remember too it is very hard to find a heat pump that will put out 400k BTU/hr so heat pumps take a lot longer to heat a pool than a gas heater. If you keep the pool heated all the time, it is not an issue but if you are looking for a faster heat up, gas is the way to go.
Using the above numbers:
Gas Heater: 100,000 BTU/hr/$
Heat Pump: 89,500 BTU/hr/$

So the gas heater would be slightly less expensive (more BTU/Hr/$).You would need a heat pump with a COP greater than 5.6 before electricity becomes less expensive.

Given that gas heaters will heat a pool much faster, that is an additional benefit.
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
If I had NG, I'd have a gas heater, no question. Since i only have LP, that's why i went with the heat pump. I dont want to spend the money to keep the pool where I like it with propane.
 

newpull

Member
Aug 16, 2009
15
Southestern PA
bk406 said:
On a 20,000 gallon pool, it would take ~22 hours to raise it 8 degrees.
Don't discount the convenience factor.

That's fine if you know 22+ hours ahead of time (could be more depending on temp or pool size) that you are going to want to use the pool and/or know you need to heat it.

For example, I'd hate to fire up the heat pump a day+ before a weekend so the kids could swim, then have them decide that they don't feel like swimming that weekend... :rant:

If you use your pool a lot and want to keep it warm over an extended period of time, the heat pump is likely best.

If you want to spot heat it on demand/on occasion, gas might be best.

Also don't forget that although the cost of electricity may be less than gas to get it to the same temperature, the heat pump unit itself costs significantly more than the gas heater (and potentially require upgraded electrical service to the pool), so there may be some time before you reach a break even point with energy savings. Again, you'll recover this faster if you heat the pool a lot.

One thing that is difficult to know for a new pool owner is exactly how much "a lot" is...
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
All good points. For us, we keep the pool heated all the time. I really dont care if anybody is using it on a given day or not. I just like to keep it heated. With the heat pump, that makes more sense anyway. The only time I really need to heat the pool more than 5-6 degrees is at the beginning of the season.

In terms of the initial cost. Yes, a HP does cost more. But, the cost of running a gas line, potentially upgrading the meter, or getting a 200 gallon propane tank installed and running all the lines for that can actually offset the increased HP cost. Generally, if it's a new pool, electrical work needs to be done anyway so running an additional 50 amps is not that much more expensive. i'd say once you figure the install cost of NG or propane, it would all come out in the wash. Also, i'm not that big on figuring the cost of something like that and amortizing it over time. So if the HP cost $1000 more, I dont figure how long will it take to recoup the extra cost. You can burn a $1000 worth of gas pretty fast. Besides, once I buy something like that, i just look at how much it cost to run out of my pocket. Once it's bought, i really dont care what the initial cost was, buts thats just me.

And yes, if your not going to keep your pool heated 24/7, then gas is much more convenient. I'm really not advocating for gas or a HP either way. i'm just pointing out costs for running each kind. It all depends on a lot of variables which kind of heat is right for a given application. How you use the pool, electric rates, gas rates, all go into the decision.
 

FLA Rider

LifeTime Supporter
Aug 8, 2010
23
Jacksonville, FL
I am in the process of getting a pool/spa built. I am looking at all the same issues. I am planning on having a gas LP heater for the spa, but not sure if to use it for the pool. Looking at having a HP for the pool. Can you use both? Have the gas bring the temp up to say 83 then switch over to the heatpump. I am looking at the Pentair EasyTouch or the IntelliTouch

Marc
 

Rico Laguno

Active member
Aug 19, 2010
35
Nyack, NY
Are there any concerns with using a Gas Heater and a Salt System?....I read somewhere that there are issues with corrosion, but i cant find the specific post.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
This post lists some manufacturer warranties that imply you should get a corrosion-resistant heat exchanger such as one made from a cupro-nickel alloy (or from titanium). Higher salt levels increase conductivity and higher conductivity increases metal corrosion rates. Using more corrosion-resistant metals would be prudent.
 

cadillac

In The Industry
Dec 22, 2008
82
FLA Rider said:
I am in the process of getting a pool/spa built. I am looking at all the same issues. I am planning on having a gas LP heater for the spa, but not sure if to use it for the pool. Looking at having a HP for the pool. Can you use both? Have the gas bring the temp up to say 83 then switch over to the heatpump. I am looking at the Pentair EasyTouch or the IntelliTouch

Marc
Basically, yes.
 

cadillac

In The Industry
Dec 22, 2008
82
Rico Laguno said:
Are there any concerns with using a Gas Heater and a Salt System?....I read somewhere that there are issues with corrosion, but i cant find the specific post.
No different than usual. Keep your chemicals inline and you're golden.
 

offgrid

Well-known member
Aug 17, 2010
87
Ottawa, Canada
I have the Hayward Gas Heater H Series (installed August 12/2010) and notice the smell of gas whenever I Ist turn it on (and sometomes longer). I have never had to run the heater more than 1 or 2 hours to get the pool temp to rise 5 degrees. (from 75 up to 80)

I contacted the installer and he said that it will have a smell for the 1st 30 days or so as silicone etc burns off the new heater. I think that it smells like gas and I also contacted Hayward - they told me that yes there will be a "smell" ... If I am concerned I should contact a liscensed Gas technician.

It has 84 % Efficiency and some Mechanical Engineers tell me that that is just the smell of the 16 % in-efficiency. My gas furnace is 90 % Efficienct and I notice a similar smell from the horizontal exhaust pipes at the side of the house.

Anyone else notice this "smell" ??
 

learthur

Gold Supporter
LifeTime Supporter
Sep 9, 2008
243
The Woodlands, Texas, USA
Heat pump is more efficient and the way to go IF you want to heat your pool everyday, use a pool cover religiously, and realize the COP and BTU output drops significAntly as the ambient te
P drops below 66 degrees.

For you you electric rates are higher than mine but your NG rate is half mine. Given your cooler climate the NG may be your better choice.

Remember heating a pool is a lot like heating the grate outdoors and is a lot of money regardless how you do it. Solar can help a lot if you have the space and sun for it.
 

offgrid

Well-known member
Aug 17, 2010
87
Ottawa, Canada
I find that the Solar blanket really helps retain the heat at night, but as soon as the sun rises it is better to pull the blanket off and let the sun hit the water. Our pool is 18' x 30' and the Salesman wanted to sell me a 40' x 20' solar blanket for $150 - and then cut to shape.

I decided to go with 2 - 18' (dia) circles for $40 each. ($80 total)

The pool shape is created by 2 overlapping 18' diameter circles- so I was able to cut the overlap and use it for the remaining shape that wasn't covered. The 2 circles are easy to pull out and fold into halves and sit against the fence. I'll take photos and post to my blog.

WIth the solar blankets on at night the pool temperature only drops by 1 degree. Without the solar blankets, the Temp. drops by as much as 10 degrees (celsius) in one night - as it did last night when I forgot to put them on and the temperature dropped to 10 degrees celsius.
 

BQ

Well-known member
Jul 15, 2013
92
Back from the dead....Any input on a solution like this?
solar PV combo with Solar Hot water too.
POWERTHERM
? Developed to maximize the thermal return of the hybrid panel
? Contains an extra layer of low-iron solar glass to aid heat retention
? Produces approx 80% of an equivalent standard thermal collector and also produces electricity.
? Peak Panel Outputs:
? 170w Electrical
? 610w Thermal (2,080 Btu/hr)
? Size of Panel = 860x1660x105mm
? Type of PV cells: Mono-crystalline
? Weight: 34,4 kg.

I would have 8 of these to heat an 18' x 44' IG.
 

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