Pool Heater, Heat Pump or Both?

[lissbpp]

I have community propane in my subdivision. Looking at installing a spa with my pool and I am considering purchasing both a heater and a heat pump and using the heater as backup for the heat pump to heat my pool during colder months. Curious if others have done this and if I'm off-base with my thinking?:
1. My home heating bill can get extremely costly during the winter months due to the propane.
2. I'm looking at the pool heater as primarily being used to heat my spa (it's 400K BTU however I'm concerned of the cost to heat the 27K gallon pool).
3. If I'm wanting to heat the pool I would rely on the heat pump with the understanding that it's relative to ambient conditions and maybe I can get an extra month or three out of my pool season (In Texas) and have a more efficient way of accomplishing this.
4. Heat pump is around $4K with the cool option (Pentair). I figure the cooling might be nice in August as a bonus.
5. Heat pump may pay for itself in a relatively short amount of time based on my back of the napkin calculations (<24months).

Your thoughts are appreciated.

 

[CJadamec]

Instead of a propane heater combine your heat pump with solar panels.

A 400kBTU heater is roughly 4x the size of your home heating furnace/boiler. If you already think heating with propane is expensive in the winter you will very unhappy with a propane fired pool/spa heater.

 

[PoolGate]

Heating your pool with propane is going to be expensive. If you want heat, however, in the off-season, it is the only option. Solar and heat pumps are only good when it is already warm out. Decide how important heat is and if it is important. bite the bullet and do what you need to do to get actual heat. Getting both is a great idea. You don't have to use the propane if it becomes too expensive. But you'll have the option at least.

 

[zingerhill]

I installed a heat pump in NY this year and it was great. Really cheap to operate keeping the pool at 86 degrees. I kept the pool open as long as the air temperature was above 70. However, i have a solar cover and that makes a huge difference. It probably won’t be nearly as good if left open.

 

[pooldv]

We've got solar a heat pump and a solar cover and we are happy with where we are. We start swimming in March and swim most of October. More about heating our pool in my pool thread, link in sig.

 

[rickv]

We got a pool cover, 9watt electric heat pump and 5KW solar panels since a month and a half. Works wonders. (I must say I live in sunny Western Australia though). I will turn it off during winter months.

 

[Swampwoman]

Lisbpp, are you building a new pool and considering adding the spa, or adding a spa to an already constructed pool?

I ask because as CJ pointed out, I also don't think you're going to be happy with the cost of a propane fired spa if you find your home heating costs excessive.

At any rate, one option to consider is a stand-alone spa that operates off of 240 v. And does with the heavy insulated cover. You're then heating efficiently and retaining heat well. I keep mine at 104 round the clock and its always ready.

You may find that for comfort and therapeutic value, you like the standalone spa much better. That is often the case.

 

[bamachem]

I found this awesome calculator. You can get your $/therm rate for NG from your local utility or by google search.

SWIMMING POOL ENERGY TEMPERATURE CALCULATOR | Neil Anderson

The cool thing about this calculator is that you can add solar heat, natural gas, heat pump, thermal blanket, etc. Lots of choices to see what each would do.

Here's a few calculations I did with the tool. I used Mobile, AL for location, 525sqft for pool size, and 78F for desired temperature.

In this one, I was looking at the swim season for a 78F pool water temp using 4 conditions:

1. Base Pool as installed
2. Base Pool with Thermal Cover Only
3. Base Pool with Thermal Cover and 80sqft of Solar Heater
4. Base Pool with Thermal Cover and 120sqft of Solar Heater

^ For me, this is the one that tells me where I need to spend my money first. In my location, a transparent pool cover ($100 worth of bubble wrap) is by far my best investment.



This one is the same pool and same desired temp, calculating the costs to heat it in March, April, and October via Natural Gas:

1. Base Pool with Natural Gas Heater Only
2. Base Pool with Natural Gas Heater and Thermal Cover
3. Base Pool with Natural Gas Heater, Thermal Cover and 80sqft of Solar Heater

^ This one also proves the value of a cover if there is any kind of heating at all to be used, even solar. Look at those annual costs drop when a $100 pool cover is utilized.



This one is the same pool and same desired temp, calculating the costs to heat it in March, April, and October via Natural Gas (runs 1, 2, & 3) in comparison to a Heat Pump (runs 4, 5, & 6):

1. Base Pool with Natural Gas Heater Only
2. Base Pool with Natural Gas Heater and Thermal Cover
3. Base Pool with Natural Gas Heater, Thermal Cover and 80sqft of Solar Heater
4. Base Pool with Heat Pump Only
5. Base Pool with Heat Pump and Thermal Cover
6. Base Pool with Heat Pump, Thermal Cover and 80sqft of Solar Heater

^ This one tells me that if I use a pool cover - already decided that with the two above - then a Heat Pump is only going to save me $100/year over Natural Gas heating, but the install expense is about $6k for a HP versus $2k for a NG heater system. It also tells me that if I do a base heater plus solar, the solar isn't going to save me much money at all in the long run and will have a payback of several years, so likely not worth it unless I wanted to use the solar panels as radiant coolers during August and September when the pool temps can soar here.

 

[PoolGate]

I found this awesome calculator. You can get your $/therm rate for NG from your local utility or by google search.

...abridged..

Interesting chart but I have issues with the temperature. Who sets the temp at 78? That is COLD! I keep mine over 90 and I think most people are 85 average. I think those cost numbers are all going to be significantly higher with a temp adjustment.

 

[bamachem]

Interesting chart but I have issues with the temperature. Who sets the temp at 78? That is COLD! I keep mine over 90 and I think most people are 85 average. I think those cost numbers are all going to be significantly higher with a temp adjustment.

I was just looking at making the water warm enough for my kids to swim.

So, I looked at 80F, 85F, and 90F water temps, using Natural Gas Heat Only, NG heat with Pool Cover, and NG heat with Pool Blanket and 80sqft of Solar. I did this for March, April, May, and October. June through Sept we should have 90F water here without any heat and mostly without a cover. Where it lists "Shaded Pool" - I set my shade to zero because we got rid of our trees in our back yard to keep the pool clean and warm.

Here's the results. Once you add the Pool Cover, the costs are not all that bad.

 

[PoolGate]

I was just looking at making the water warm enough for my kids to swim.

So, I looked at 80F, 85F, and 90F water temps, using Natural Gas Heat Only, NG heat with Pool Cover, and NG heat with Pool Blanket and 80sqft of Solar. I did this for March, April, May, and October. June through Sept we should have 90F water here without any heat and mostly without a cover. Where it lists "Shaded Pool" - I set my shade to zero because we got rid of our trees in our back yard to keep the pool clean and warm.

Here's the results. Once you add the Pool Cover, the costs are not all that bad.

Thanks that is very informative. Can you post the link to that site?

 

[bamachem]

Thanks that is very informative. Can you post the link to that site?

SWIMMING POOL ENERGY TEMPERATURE CALCULATOR | Neil Anderson

Once you enter your data and run a calculation, you can go back up to the top and click the button to run another calculation. The results will be in tabular format like I've posted.

Once you want to clear the table, just refresh the browser.

 

[PoolguyinCT]

If you have the buy in funds, fossil fuel heater & a heat pump is a great 1-2 punch..

 

[Dirk]

Some random ideas to consider... a little devil's advocate for ya...

If you're doing all these calc's for gas and heat pumps, etc, I'd gather them up and then go talk to a couple of PV solar installers. Not just pool-water solar, I'm talking about electric-generating solar. See what the PV sales guy can add to your equations. All gas is expensive (like, really expensive, as others here are pointing out), and its cost will continue to climb. PV pays for itself over time, sometimes just in a few years. Then it's "free" for the next 25 or 30.

Are you wanting to heat the pool, or just the spa? Even if I could get my pool warm enough in the winter months to swim, I wouldn't likely. My pool use is during the "warm air" months and I don't have much interest in getting wet on a cold day, no matter how warm the pool water is. Now if I had a spa, and could heat it with 240V (as suggested above), and that 240V was "free" (from PV solar), then, yah, I'd keep it at 90+° 24-365, and use it a lot, all year round...

If my g-kids are any indication, they'd just as soon get in a spa as in a pool, especially on a winter day (as would I).

So ask yourself, how are you really going to use those two bodies of water, and when? And how much are you willing to pay to do so?

Oh, and don't forget to calculate replacing that heat pump, at, what, $5K a pop? I've heard they don't last all that long. PV solar systems come with 25 year warranties. Water solar systems up to 12 years. Heaters? Not so much!

Dump the pump, dump the gas heater, put that money into two solar systems:

Water-solar for the pool in the warm-air months, PV-solar for the spa year-round. I think you and yours would get plenty of fun that way. Your kids will be happy with both. And after about a half dozen years or so (after these systems pay for themselves), your heating costs will be zero. Maintenance cost will be near-zero, too. Try to match that with any kind of gas or pump solution...

Oh, and while I won't argue the heat-retaining benefits of covers, I wouldn't (and don't) use one. Looks like heck. Most of the enjoyment I get from my pool is looking at it! And I know I personally would not use my pool as much if I had to take on and off a cover every time I wanted to jump in for a quick cool down. Or what, drag it off in the morning, back on at night? No thanks. Plus, I'm not sure what a cover does in terms of keeping a pool clean. Some say it's better, others say it makes it worse. Sure, it catches the leaves, but then what, you slide the cover out of the water, what happens to the leaves? You have to clean them off the cover, or do they slide off into the pool (or both). I don't imagine a skimmer can do its thing with a cover on. So no, no cover for me.

Point is, your calc's might look good on paper (or not), but you have to really consider how you're going to actually want to use your pool and spa, how much your going to pay over time, and how much you're willing to deal with a pool cover...