Deciding between natural gas heater and electric heat pump

[lhlsea]

My natural gas heater was DOA when we moved into our place in September and I am in the process of trying to replace it. I am having trouble deciding between natural gas and electric heat pump. I have read a ton here and elsewhere and generally understand the differences -- my main issue is assessing possible operating costs since I don't have any historical info on my specific pool.

The pool equipment guy I am working with (who is great) is somewhat on the fence. I think he is leaning toward thinking we should go electric but hasn't installed quite as many (relative to gas) to have a good feel for the ongoing costs.

We have a 17k gallon in-ground and are in Seattle. Ideally we could use the heater to give us some extra time on each end of the season plus keep it up during the summer.

For the upfront costs:
- currently have natural gas and the gas meter is right near the equipment.
- cost of equipment (incl install) would be $3000 more for the heat pump (compared to gas)
- this 3k doesn't include upgrading the electric for which I have a quote of $1100 and it'd be a bit of a pain
- so total of $4100 more upfront to go electric

I ran a couple of the calculators for ongoing costs.

Roughly it seemed like gas could cost somewhere in the $2000-3000 / year (!) and electric would be about half of that - $1000-2000.

Obviously this depends on the assumptions I use but I was trying to make my best reasonable guesses and generally focused on May/June through Sept/Oct.

At those high costs an electric would pay itself back in only a few years and might be worth it.

However -- those numbers are without a cover which I have read here makes a big difference. I don't have one but could certainly get one, though my pool shape and fence situation would make it tricky.

Using the calculators WITH a cover shows much lower costs, like $500 /year for gas and $200-300 electric. In this scenario I would probably stick with gas since the payback is long and electric means dealing with an extra contractor and install.

All that said, I have no practical experience and worry that I am over focusing on the calculators with possibly bad assumptions.

I'd love any practical experiences people could share (especially if your weather is anything like Seattle) that might help me. Even just some actual operating costs you have seen in practice that I can benchmark against would be really helpful, or advice on anything I may not be thinking about.

Thanks very much!!

Lewis

 

[mwalling]

Lewis, I'm assuming you are going to use the pool all year? What's the average daytime water temp in the winter?

 

[JoyfulNoise]

It really all depends on if you plan to cover the pool. Without a pool cover, it really makes no difference because all of the heat you put into the pool will be gone the next day. You've already said that your pool's shape and location does not make it seem easy to cover....I'm in the exact same situation. I don't cover my pool because it is a royal PITA and so even contemplating turning the gas heater on to the pool makes me queasy. The spa is the only thing that gets heat from my gas heater.

SO I would say BEFORE you decide on what heater to get, you need to figure out how to cover the pool in a manner that doesn't require a 5-man crew to deploy the cover. Then, after you figure that out, you can make a better choice on the type of heater....

 

[lhlsea]

Thank you Joyfulnoise, that makes sense.

Mwalling - all year would be nice but I think that'd be prohibitively expensive. The numbers I mentioned were based on May/June to Sept/Oct which is what I have heard is the norm here in Seattle.

 

[mtbarr64]

Skip the Heat pumps. Guaranteed to run 24 hours a day.

The love to quote a cost of $/hr of operating time. Gas shows $$$$/hr and heat pumps $/hr, so much less! Lol.

They fail to tell you that you get 400,000 btu with the gas heater per hour instead of 35,000 btu with the heat pump.

Running the heat pump longer at a lower rate adds up fast!!

If you have a gas line use it.

 

[mtbarr64]

If you think you are going to heat a pool in Seattle for $200 a year on electric you will be shocked.

You will pay about $300 per MONTH with gas and double that for electric. Electric for heating water is THE MOST INEFFICIENT means. Skip the sales Baloney Sandwich!

Go gas. Use the existing line. Be prepared for $400 a month.

 

[pooldv]

Yes, a solar cover makes a big difference by reducing heat loss overnight. I am very happy with our combo of solar panels and a heat pump. Heat pumps are very efficient in terms of btu per $ of energy. Since adding the heat pump last fall we swam all of October and we've been swimming since March 13th this year, in prior years we couldn't swim until early-mid May.

More here, How Much Does it Cost to Run My Pool Heater? - INYOPools.com

- - - Updated - - -

If you think you are going to heat a pool in Seattle for $200 a year on electric you will be shocked.

You will pay about $300 per MONTH with gas and double that for electric. Electric for heating water is THE MOST INEFFICIENT means. Skip the sales Baloney Sandwich!

Go gas. Use the existing line. Be prepared for $400 a month.

Electric resistance heating is the most inefficient way to heat, not a heat pump. We spent much less than 100/mo.

 

[ps0303]

Gas.

 

[waterl0gged]

We had the same decision about 2 years ago, except we didnt have any heater at all , so no replacement money savings to factor in .
For us it was either Propane (and the tank install to go with it) , or a Heat Pump .
The Heat pump was approx twice the cost as a propane unit ......up front .

In the end , I am glad we went with a heat pump . We decided to go with our local company brand (just in case we ever had problems) of heat pump and chose a Heat Siphon Z575 HP Digital for our 25,000 gal pool (18' x 36' , 8' deep end) .
It cost more up front , and with the cost of the unit, and wiring install , we were about $3800 . (got the unit direct from Heat Siphon as we are pretty close) .
We keep our pool set at about 88 degrees , and the electric up charge with the heat pump addition costs us between $30 - $50 a MONTH ! So, if we estimate on the high end of $50. per month x 6 months , our pool heat costs us about $300. ...........at 88 degrees , 24/7 .
We would be paying that for propane every month , if we chose a gas heater !

We do have a pool blanket (solar cover) , and that is prob one of the most important items you need to think about if you install any heater . Without the solar cover, you will be throwing most of your heating $$$ away . If you cant do a solar cover , its not worth getting a pool heater unless you are ready to spend a great deal of $$$ on either nat. gas OR electric.

The heat pump heater was probably one of the best investments we could have made for our pool "time" . I knew that heat pump heaters were pretty efficient, but I am still in shock at how efficient they really are . Our electric bill is still a pleasant surprise every month in the summer . I surely would have thought it would cost more $$$ to heat our pool to the 88 degree range , but it doesnt .
The only downside vs a gas heater , is you will not get a fast temp rise initially with a heat pump . Once you get it to your desired temp ..........it holds it there NO problem though !
We LOVE our heat pump pool heater !

BTW, our heat pump model has a rating of about 127,000 BTU with a COP of 6.7 !!!
More than enough to feel very warm water, efficiently coming out of the jets !

Here is a picture of it ............

 

[Nectarologist]

Hi. I copied the below from another thread I replied to last month...I hope it helps. I can't imagine it wold cost 2-3k to heat of the season on gas but check your bill for your costs (mine listed below). I'm about 20 minutes NW of nyc so you can see how your average temps compare.

I open in early May and don't heat until the third weekend in May. From that point on the heater goes on daily until probably mid June. To give you an idea, our nighttime temps in early May average in the 40s (southern NY). By mid May through the month, the average low is 50 and climbs every few days. By mid June our average low is 60. I've tried the liquid solar blanket one year and I don't know if it works or not. A couple of points though...if I know we won't use the pool for a few days I may turn the heater down (if I remember which hardly happens) to 80. For example it's going to rain for a couple of days straight. If I had to guess I'd say the pool heats about a degree per hour when I'm going from 84 to 88. My key indicator is how cold does it get at night. That's when I lose the most heat since I get full sun during the day. As an FYI, by me I found that when temps stay above 70 overnight my heat loss is hardly anything (especially when it's humid as my area can get). So if you get a blanket you'll learn your norm and when it's worth putting back on and when you can leave it off.

Also I don't know how much gas costs by you (I'm at .62 / CCF plus gov surcharges on top) but if yours is double of course it would be more to use. I looked at last year's bills (total gas charges). My March 25 to April 25 bill was $72 (didn't have pool open, but heat on at night in house). April 25 to May 23 was $45. May 23 to June 24 was $163 (lots of heating and grilling by then). June 24 to July 25 was $86. July 25 to August 25 was $49. Then August 25 to September 27 was $57. I remember that I didn't heat the pool all that much in September last year. I hope this helps a bit. The last thing you want is to get a whopping bill that's a ton more than you expected. I just remember thinking it was going to be $400 more to heat the pool per month and was relieved it wasn't close to that. Note my minimum service charge is $30/month I think (weather I use any gas or not). So that & a lot of grilling make up about $60. So about $100 max to heat the pool for one billing cycle.

 

[lhlsea]

Thank you all for all of the great info. Really appreciate it. Conceptually I think the heat pump is worth, though the upfront extra $4k (including electric work) is the part that is tough to stomach.

 

[waterl0gged]

Thank you all for all of the great info. Really appreciate it. Conceptually I think the heat pump is worth, though the upfront extra $4k (including electric work) is the part that is tough to stomach.

Yes, that is a tough call . Payback time frame for the heatpump over the nat. gas unit may take a long time .
I LOVE our heat pump , but in your situation I may have been swayed to go with the gas unit . Everything for nat gas (in your case) is already in place for hook-up , and it will be easy installation and WAY less $$$.
4k is a BIG difference in price for a heat pump , it will take a while for that rate of return to overcome the cost difference .

Our decision was easy because we didn't have a heater at all . The difference in price was not that dramatic , plus our only other choice was propane . If we had Nat gas .........it would have been a harder decision.

Good luck in your decision !!!

 

[pooldv]

Yes, you can buy a lot of pool heat for 4k.

 

[JoyfulNoise]

I just reread Post #1 because I was confused by your $4k number but I see now that, in order to install the heat pump, it will cost you ~$4k over what the gas heater would cost. If that is the case, then the answer seems obvious to me - gas. Even if you assumed a problem free, no expensive repairs needed 10 year operating window for both heater types (which is a pretty huge assumption), there is no way you will find enough operational differences in cost between the gas and electric heater to ever make up the difference in initial install costs. If there isn't some obvious $400/year difference in running them that you can count on being there year after year for ten years, then the heat pump makes no sense.

I also still believe/agree the cover is the key here and if you cover the pool when you want to heat in the elbow seasons, then it matters very little if you are using gas or electric to generate the heat.

 

[lhlsea]

Thanks. One thought I just had -- I am going to try to contact the prior owners to see if I can get some historical info and costs from them. That would probably help quite a bit.

I don't really know anyone else in our neighborhood with a pool, though I can see a few on Google Maps satellite view so perhaps I should go knocking on some doors for advice .

Finally, seems like a cover will be critical -- my pool shape and space is tricky so I will start a separate thread to ask for advice on that.

TFP has been hugely helpful to me as a newbie -- thank you!

 

[ps0303]

I still don't see where you're going to spend $2000-$3000 a year on gas just to heat the pool. Even $500 a year seems like a way off number.

In many places natural gas is alot cheaper then electric plus you're getting real heat.

 

[lhlsea]

I still don't see where you're going to spend $2000-$3000 a year on gas just to heat the pool. Even $500 a year seems like a way off number.

In many places natural gas is alot cheaper then electric plus you're getting real heat.

Thanks, I hope you are right. I definitely don't have the experience to have good judgment so might be way off.

The screenshot below has the assumptions I used for the noanderson calculator and a spreadsheet I made with the results. There were a few other similar calculators I tried and they were in a similar ballpark.

 

[cjpwalker]

Wish we could have went with gas just for the recovery time. I have gas at the house, but getting it on the other side of the garage where the pad is just wasn't feasible, so we went with a heat pump. The heat pump falls on its face below 50, and is pretty much useless in the 30s. I modified the defrost controls to squeeze a little more run time out of it in cold nights and adjusted the refrigerant charge to dial it in as tight as I could... Even in the 50s, though, heating the pool up is not realistic - it needs to run all the time to maintain (which means my pump runs 24/7). With a gas heater you can fire up the burner and be swimming in an hour or two.

 

[mwalling]

I still don't see where you're going to spend $2000-$3000 a year on gas just to heat the pool. Even $500 a year seems like a way off number.

In many places natural gas is alot cheaper then electric plus you're getting real heat.

Depends what the temperature is...I spend 35-40 a week to move it from 60 degrees to 88 and hold it. I spend $350 to move it from 42 degrees to 88 and hold it...

 

[mtbarr64]

Thanks, I hope you are right. I definitely don't have the experience to have good judgment so might be way off.

The screenshot below has the assumptions I used for the noanderson calculator and a spreadsheet I made with the results. There were a few other similar calculators I tried and they were in a similar ballpark.

Where did you get this? What are the formulas behind those cells?

Having had pools forever those numbers just don't add up. I noticed you are using therms, that is a billing calculation number.

You need to use actual btu (gas) and kwh (electric) converted to btus to determine the energy need to change the temp of the water.

Home heat pumps use heating strips (resistive heat) as backup when the units cannot produce enough energy to meet the demand. If these pool units have none then the system is useless below 50F. Gas will always produce.