Heater and Heat Pump?

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jurmanji

Active member
Sep 14, 2015
43
Los Angeles
Putting in a new inground pool/spa with auto-cover 14,000 gallons. Live in Socal. Is getting a heat pump worth it? Pool builder doesn't think so since cost is around $6,000 and humidity is a major compnent of how it works and LA has little humidity. But we will have solar soon. Any thoughts?

Thanks!
 
Leave space on your equipment pad for a HP and enough electrical power for a 240V 50 amp connection and live with your pool for a season or two. You will decide if the HP cost is worth it to you.
 
I also live in SoCal and ran though this same calculation myself. If you have the money and want to truly be green, then a heat pump in conjunction with enough solar power to run it would be a great solution. But you will need a LOT of solar, probably double whatever you currently have planned.

If you just want to extend the season a bit (or if you live near the coast and need heat mid summer) then the solar water heating panels might be an option. But be aware that their efficiency drops rapidly as soon as the air temperature drops much below the pool temperature. If want to actually swim in the winter time, and don't want to burn fossil fuel then solar electric plus a heat pump is probably the best (but very expensive) solution.

I went with a 400k BTU natural gas heater. Also my pool is much smaller (6100 gal) so I can easily heat it in an hour two for a weekend swim in January (like I did today).
 
jurmanji said:
Putting in a new inground pool/spa with auto-cover 14,000 gallons. Live in Socal. Is getting a heat pump worth it? Pool builder doesn't think so since cost is around $6,000 and humidity is a major compnent of how it works and LA has little humidity. But we will have solar soon. Any thoughts?

Thanks!
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I have a huge heat pump, and it works very slowly to move the temperature and takes a lot of electricity. In my case, I also wanted to chill the pool, so the heat pump is fine. I’d go with a gas heater unless you also want to chill the pool.
 
Putting some numbers into the equation for your 14,000 gallon pool with current SoCal utility rates:

With a 400k BTU/hr 84% efficient gas heater it will take about 3.5 hours to raise the temperature of the pool 10 degrees. The heater burns 4 therms/hour, and the current rates for gas from SoCal Gas are just about $2/therm for usage over baseline (which you most likely will be doing). So cost to heat the pool 10 degrees with gas $27.80

I looked up the Jandy heat-pump J2500T (because they have reasonably detailed specifications online). For a heat-pump the performance varies quite dramatically with air temperature. On an 80 degree day you can expect it to take 10.6 hours to heat your pool 10 degrees. At 5.55 kW that works out to 59 kWh, SCE currently charges 0.30/kWh (off peak) so that works out to $17.10, quite a bit cheaper. With 50 degree air the time rises to to 15.8 hours, and the cost to $25.41, surprisingly still cheaper than the gas heat.

If you are in the DWP territory (or one of the other city-owned utilites) your rates may well be cheaper than SCE, and that will tilt the equation further in favor of the heat pump.

Humidity has a relatively minor effect on the performance of the heat pump. The main factor is the temperature difference between the water temperature and the air temperature.
 
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I guess for me, what I would ask, what is your intention? Is it to heat the spa when you want? Or is it to heat the pool to extend your swim season? Being in SoCal your swim season is already pretty good and long. I say because I lived in South Orange County, until moving to Las Vegas in 2019. To heat the spa, the quickest, in my opinion would be to get a 400k btu heater. If you are surrounded by two story homes and your pool will be shaded most of the day, the pool water probably won’t get above 82 degrees in the heat of the summer. So, there is that consideration. What is your intention?
 
The idea would really be the most cost effective. My wife and I use the spa almost every week and my son is learning to swim so he will probably be in it a lot. We have a pretty big house so am looking at a fairly large solar system. I'd love to pay both DWP and socal gas as little as possible :)
 
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