Help decide: Gas or Heat Pump

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crek31

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Jun 28, 2009
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Looking for guidance on which type of heater I should pursue. Any input will be much appreciated.

POOL INFO:
* Above Ground Pool either Seasonal 18' x 48" Intex or Permanent 15' x 30' x 52" Garden Leisure
(so 7646 gallons to 10,620 gallons)
* Location is Lincoln, Nebraska
* Wanting it to be 88 degrees June to September and possibly May to October depending on how expensive this ends up
* Want it ready to swim in after work/school with little notice M-F and all day SA and SU
* Would like to do SWG unless that is ill-advised with a heater
* Have a solar blanket and pool is in full sun about 1/2 the day and shaded the rest.


MONEY CONSIDERATIONS:
* Have had a quote of $2000 to run gas line to pool site. Still possible it will be much cheaper, but two different contractors said I'd have to run it from the meter on the side of the house because for some reason (?) I can't go out back wall of house off furnace room. This could be a huge swing in cost if I find someone who can do what looks like the easiest route and go through the back wall -- but for now I guess worst-case is $2000 for the line.
* Looks like I need a new electrical panel if I do the heat pump -- no firm quote on that as yet, but several years ago when looking at putting in a second oven the estimate for that was $1700 for a new panel. Pretty sure I'll need the panel for a heat pump and pool pump :(
* DIY is not an option, so please don't assume I can greatly reduce the costs set out above.

*Electric rates are 4.75 cents per kWh for usage above 900 kWh, which I am.
*Gas rates are .78097/therm
(note, I usually just look at how much money to pay, so hopefully I correctly recorded the rates -- if they seem wacky tell me and I'll see if I have it wrong)

If there is other info that is needed please let me know. Thanks in advance for any direction on which is my better choice -- factoring in cost and usage.
 
bk406 -- I only ask because I've seen you post equations in other strings -- if it is a pain, just say so and don't do the work. Let's just say I want to get water that starts at 80 degrees up to 88 degrees. Is there an easy way to tell me how much it would cost and how much time I'd have to wait for it rise using gas? For the sake of this discussion, I guess assume I'd get 150,000 btu gas heater (which I think is over-kill even for the oval pool I'm considering).

Second -- would you get gas heat if you were to do it again?
 
Ok, lets see. I'll see what i can do here. I have a head cold that would kill a normal human and I'm not thinking so straight right now, LOL

Few things first.
1) Your 4.75 cents per kw. Does that include tax, generation charge, etc? You have to figure that in when you calculate electric rates.

2) You probably will have to raise it more than 8 degrees but for discussion, lets do 10
3) 150,000 BTU gas heater is wimpy. Get a 400,000, even for a small pool. Sure it will use a lot more gas, but the use is close to linear. In other words, a 200k heater will use 2 therms an hour. A 400k will use 4 therms per hour but you only ave to run it half the time, so the gas uses is about the same.

4) A heat pump in your area will not keep your pool at 88 degrees in may or september, much less early october, so thats a consideration beyond cost. You would be lucky to get it to 80 or so.

5) A 120,000 BTU heat pump is around 4K. A 400,000 BTU gas heater is around 2k. The gas line vs the electric panel is a wash, so the cost up front for gas is less.



A 10 degree rise with 400,000 BTU heater for your size pool (use 10,000 gallons) will take 2 hours. At 78 cents per therm, that about $6.25. For a 120,000 BTU HP (and you wont get 120,000 out of it in the spring and fall, lucky if you get 80,000. So, at 80,000 BTU and 5 cents per kW/hr, it would take 10 hours and about $3 in electricity.

So about half the cost, but 5 times the time to heat. And I promise you on cool days at say 63=65 degrees, all it will do is spin the electric meter.

These are pretty rough calcualtions, now. It doesnt into account the increase in costs for power due ot taxes, transmission fees, etc. Also, I forgot to de-rate the gas heater for efficiency. You wont get a total of 400k out, more like 85% of that. But, that being said, everything I've seen and the numbers i've run based on gas rates of ~ $1 per therm and electric rates including other charges of between 10-20 cents, you can heat a pool about as cheaply with gas as you can a heat pump and do it much faster and more conveniently.

I would get a heat pump again since I do not have natural gas, only propane. Propane is really expensive to heat a pool with. What I would have done is gotten a propane heater when I put the pool in instead of waiting until this spring to do it. A heat pump works really well during late May-late august to take the chill off. But in a climate like yours and mine, in early spring and into fall, not so much
 
bk - thanks so much for your time and effort, especially when you are feeling bad! I think you've sold me on gas. If my worst case scenario proves true -- that is, I need a new panel even if I don't do a heat pump AND the cost of the gas line really is $2000, I'll repost to be sure gas is the winner. For now I'll proceed with figuring out pool placement and secure a guaranteed quote on getting gas to it. I love the input that a 400,000 btu unit gets me a warm pool twice as fast. Last year there was a used but seemingly reliable 400,000 btu unit for sale locally by a country club and the guy convinced me it was WAY bigger than any AG pool would ever use - I think he was selling it for $600 if I remember right. Now I wish I had bought it. Go get some sleep and I hope you feel better soon! Thanks again.
 
I mostly agree with bk406, though I can definitely see using a pair of heat pumps in a situations like this one if you are serious about keeping the pool warm for months at a stretch. Keep in mind that the more you extend the swim season, the faster the costs will accumulate. Pools require noticeably more heat than most private homes. Both gas heaters and heat pumps end up being expensive ways to heat a pool. If the primary concern is cost, then go with solar panels if at all possible (keeping in mind that they will have to be large).

If solar is out of the question, the choice between gas and a heat pump has a lot to do with how you intend to use the heater. If you really want to keep the pool at 88 for two extra months on either end of the swim season, then with your electric rates a heat pump (or more likely two heat pumps in parallel) will end up being less expensive in the long run. However, and this is a big however, that isn't the way most people use their heater. Most people heat for a couple of days and then stop, repeating occasionally, both because heating is expensive and because swimming when the air is cold isn't nearly as much fun as swimming when the air is warm. Nine times out of ten people end up heating for a special party or a rare warm weekend. If you are going that route, then you want gas, because nothing heats nearly as quickly as gas, and because the heat pumps won't ever save enough to pay off the extra up front costs when you only use them a few days a year.
 
Well, now I'm confused again. I had thought the main downside to a heat pump was the up front purchase price but that after that they were much cheaper. I assumed I'd run the heat pump consistently and that once the pool got to temp it would not cost much to keep it there (at least June to September). Since my gas heater was going to be so much for install, I was further inclined toward heat pump (since I might need new panel either way). My general understanding is a heat pump will last about twice as long as a gas heater so that over time the up front cost is not that different and it comes down to function (speed and frequency of heating) and rates. All of these assumptions were from casual reading, not actual numbers crunching. I think I need to keep figuring out some of the variables like pool placement (different if Intex or permanent) and then evaluate when some things are a little more known. I'd pay a lot to have someone local I could trust to just figure it all out, get the permits, run the lines, etc. Call me when it is time to swim! Thanks for the responses:)
 
crek31 said:
. I assumed I'd run the heat pump consistently and that once the pool got to temp it would not cost much to keep it there (at least June to September).
Click to expand...

You assumed correctly. However, the point I was making, and one Jason alluded to as well, is that in your climate, you will not be able to maintain a pool temp much above 82 degrees or so in the spring and fall. You will not get the 88 degrees you want, even with a solar cover.

Let me give you examples of my climate, how i use the heat pump, and the drawbacks. FWIW, I know what your weather is like in Lincoln. I've set many a saturday at memorial stadium in the fall watching the sooners and cowboys. :wink:

Where I live, in late April to say the 3rd week of May, we get pretty decent weather during the day. High 60's to low 70's. Now, the nights are still cool; low to mid 50's. During this time my heat pump runs almost continously to keep the water at 82 degrees. It's tough since the days are still short and the nights cool. The heat pump just cant suck enough heat out of the air to get the water much above the low 80's.
Now, by memorial day into june, the night time lows are warmer and the HP doesnt run as much, but it still runs a good bit. You are correct about setting the HP and maintining the temp. The big caveat is that at this point in the year, it wont keep the pool as warm as you want. By late june, all of july and into august, the HP doesnt run much. In July, thre are days it doesnt run at all, but then again i keep it set at 82-83. During the dog days of summer, my pool can get to 88 by the heat pump and a litlte bit of sun, but that only last into the first half of august. By then, the nights are cool again the the cycle repeats until I close around columbus day.
The issue you will have with a HP is that it will not keep your pool at that high a temperature during the months you want it to given your climate. You also have to remember that most of the claims of heat pumps are based on ideal conditions. In fact, the BTU ratings are based on 80 degree air temps and 80% humidity. Thats fine for florida, but a bit unrealistic for New Englanm, or even Nebraska for that matter. Once you move down in ambient air temps and humidity, the BTU output falls significantly.

The reason i like my HP is that I can keep the chill off the pool in the early and late summer fairly cheaply. I set it at 83 or so and forget it. Between the HP and the sun, the water is nice hen i want to use it. But it will not extend my swiom season by much. Thats why I'm going to bite the bullet and get a propane heater to use in the spring and fall. In the fall, we use the pool on a warm weekend or maybe a day or 2 during the week, so gas makes sense. For us, we like 88- 90 degree water in September and may since the air temps are cooler and a HP will not do that.
 
Nebraska

Here are some numbers to crunch. :lol:
The examples below use Hayward products specifically designed for above ground pools, but the numbers will be comparable with other brands with comparable btu output.

The answer depends on how and when you will be using your pool. :?:

Hayward lists usage costs and average temperature rise for a 100k btu above ground gas heater.
http://www.hayward-pool.com/pdf/literat ... er10_5.pdf

According to Hayward, using a gas 100k btu heater with 81% efficiency to heat a 10,000 gal above ground pool would have an 8 degree temperature rise in 8 hours.

With your natural gas rates, it would cost about 85 cents/ hour to operate.

Cost with Propane 2.75 /gal or about $3 / hour to operate.

For your average monthly Spring and Fall usage here are some numbers:
Using the heater daily for 8 hours would cost $200 per month with Natural Gas or $700 per month with propane.
During months with mild temperatures, maintaining round the clock 88 deg temp could cost $250-$300/ month with natural gas depending on the average night time temperatures.

You could use a gas heater when the temps are colder, if you are willing to pay the operating cost.
Consider the cost of maintaining 48 deg F water to 88
It would take 40 hours to heat the water $35 and $16/day to maintain so 30 days would be around $500/ month.
Propane-- $1800/ month?!?!?
-------------------------------------------------------------------

Above ground heat pumps in colder climates would limit the use to months with daytime temps in the 70's.
The Hayward heat Pro Deluxe Heat Pump for above ground pools could raise the water temperature 1/3 to 1/2 degree per hour depending on the outside temperature.

http://www.hayward-pool.com/pdf/literat ... OABG05.pdf

Electricity rates in Nebraska are some of the best in the US
http://www.eia.doe.gov/electricity/epm/table5_6_a.html

These Heat pumps use 3.2kw / hour so would cost you around 30 cents/ hour to operate.
The slow temperature rise would require 24 hour/ day operation or $7 / day or $210 / month.
The advantage here would be that the pool is ready to use day or night, but only for a few months per year in your climate.

----------------------------------------------------------------------

Propane has the advantage for lower up front cost. If you plan is to use the heater only a few weekends per year and your pool budget is limited, then the propane heater might be appropriate.

If you only plan to use the pool heater for a few weekends per year, then the up front cost of Natural Gas lines and Heat Pump electrical connections compared to Propane would require many years to recover the cost.

The cost for weekend usage only for Propane is around $48/ weekend.
$3/ hour for 16 hours is $48.
Less than $400/ year for your 8 weekends/year.


Weekend usage only for Natural gas or Heat pump compared to Propane.
$2000 in additional up front costs / $2.15 average savings per hour = 930 hours to recover the savings
Weekend only usage of 16 hours per weekend for 8 weekends per year = 128 hours/ year
It would take over 7 years to recover the initial costs.

---------------------------------------------------------------------------------

Keep in mind this is only an example and the prices will vary according to your actual usage and changes in energy costs.
Electricity costs vary substantially within different regions of the US.
http://www.eia.doe.gov/electricity/epm/table5_6_b.html

For example, our friends in California and in the New England and Mid Atlantic states pay double the electricity rate of Nebraska. In those areas of the country, the cost of using Natural Gas would offer a better value especially for weekend or special event usage.
 
You can get an idea of the Coefficient Of Performance (COP) at AHRI where the pool heat pumps listed mostly have a COP of 6 at high temperature (80.6ºF air temp) and a COP of 4 at low temperature (50.0ºF air temp) where the water is at 80ºF and relative humidity in both cases is at 63%. The heat pump output rating is likely using the higher COP number so basically at lower air temps you get only around 2/3rds the rated output. On top of that, the rate of heat loss from the pool is greater when the air is cooler. The combination of these two factors is what makes it difficult for the heat pump to raise the pool temperature high enough in the tails of the season.

Even with a gas heater the latter effect of heat loss is still a factor even though the output of the gas heater doesn't change. My gas heater output is 200,000 BTU/hr which for my 16,000 gallon pool means around a 1.5ºF rise per hour. I have solar heating so during the peak of the summer I don't need the gas heater in spite of my keeping the pool at around 88ºF, but in the tail months the usage goes up a lot. I have a mostly opaque electric safety cover that I figure is about half as efficient as a bubble-type cover in terms of insulation. During the peak of summer, I only lose around 2ºF overnight. During the non-peak part of summer, so most of the season, I lose around 3ºF overnight. However, during the tails of the season I lose over 4ºF overnight and continue to lose heat during the day. The gas heater is able to keep up, but heats much more slowly when there is heat loss and obviously costs more with the longer run times. This post shows that gas is used heavily for April, October and November and used some in May, June and September. The average day/night temperature is mostly what drives the heat loss that is proportional to the difference between the water and air temperature. You can see that even the more intense sunlight for the solar in May and June is less important than that average temperature influencing the rate of heat loss.

A key takeaway is that a more insulating cover would save more energy than most any other factor, regardless of type of heater you eventually use.
 

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Poolschoolgrad,

Thats a lot of info for the poor OP to digest!

A few points.

1) A heater whether gas or heat pump is not designed to be used either with an above ground or inground pool. There is no difference, period. Size of the heater is the only difference.

2) The OP, or anyone else probably isnt going to heat a pool from 48 degrees to 88 degrees on a daily basis, so those calculations are a little superflulous.

3) The propane discussion, while interesting, doesnt really apply here becasue the OP has natural gas

4) A heat pump will use a lot more than 3 kw/per hour. Maybe a little bitty one ,might, but you wouldnt want one of those anyway. A good, 100,000 BTU heat pump will use at least 5 kw and most likely 6 kw/hour.

5) No dispute that at 5 cents per kw/hr a heat pump would be cheaper to operate. The point is that a heat pump woiuld not keep the OP's pool at the temp he wants it. It wouldnt matter if it were free to run. It wont keep his pool at 88 degrees when he wants it that warm.
(I still want to see the actual electric rates with all the other fees. My generation charge is 8 cents. Not much more than the OP. However, you add the other fees in its around 14-15 cents. California can be as high as 40 cents, so no comarson there.

I just dont want Crek confused anymore than he is. Bottom line is that, IMO

1) Given his climate, he would HATE a heat pump, and

2) given a gas rate of a buck a therm and electric rates around 10 cents including tax, title and tag, its about as cheap to heat with natural gas.

EDIT:

IMO, those COP numbers are c*r*a*p. They are based on ideal conditions. They hardly even mimic reality. Look, I'm not bashing heat pumps, they are what they are. But IMO they have been oversold as a panecia and the best thing since sliced wonder. Truth is, depending where one lives, they can be a big old hunk of metal that eats power.
 
I sure do appreciate all of you who have offered your wisdom! I love this forum! I think if I could have my pool ready to swim (88 degrees) M-F from 5:30 pm to 8:30 pm and all day SA and SU, for $250 per month operating expense (I understand the equipment is not counted in that) I'd be happy. For sure I want this for June, July, and August. Before June and after August I'd probably be willing to have it more event-based and not always at the ready. However, if it was $250/ month even for May and September I'd be willing to do that and have it always ready.

I assume if I get a gas unit and it needs, for example, 3 hours of run time to get up to temperature, that I can set a timer or something such that I don't have to be home at 2:30 so it is ready at 5:30. If I have to be home to set it, that scuttles the idea of gas.

I am hopeful Jason Lion can elaborate on his "two heat pumps in parallel" comment. Obviously that is a lot of up-front money for two heat pumps - but beyond that, how does that work? Have two going at once, or what does "in parallel" mean?"

bk406 -- here is what my electric bill insert says about 2011 costs: "Monthly customer and facilities charge - $9.45 PLUS 0-900 kWh = 6.55 cents per kWh; Above 900 kWh = 4.75 cents." My January bill shows I used 2,456 kWh for Dec 9 to Jan 11 -- the bill shows:
Energy = 132.86
Facility Charge = 9.45
Sales Tax = 9.96
 
crek31 said:
I am hopeful Jason Lion can elaborate on his "two heat pumps in parallel" comment. Obviously that is a lot of up-front money for two heat pumps - but beyond that, how does that work? Have two going at once, or what does "in parallel" mean?"
Click to expand...

Yes, you hook to heat pumps up side by side. I think he mentioned it since your electric rates are so cheap. I still think you wouldnt be happy. I dont think even 2 would get the pool where you want it. An extra 4 grand for another heat pump and the extra cost for 50 more amps of power will by a lot of gas.
 
My apologies for making the issue more confusing. :oops:

For your average monthly June - Sept usage, using a 100k btu heater daily for 8 hours would cost $200 per month with Natural Gas.
If you choose to extend the heating season from May into September, plan to spend $50 to $100 more for those per month.

A Heat Pump in your climate would be beneficial during the months of June, July and August when water temps are in the mid 70s. You would save on energy costs as compared to NG if you keep the pool heated 24/7 during these months. However, with a short swim season, it will take several years to recover the additional cost of a heat pump compared to a Natural gas heater. If you heat for only a few hours per day or only for weekends, then the Natural Gas heater has the cost of operation advantage.

To achieve your extended goal of a May thru October swim season, the Natural Gas heater is the correct choice. :goodjob:

You would not need to be home for the heater to operate.
The heater thermostat would be set to the desired water temperature but would not operate until water flow is detected. You can use mechanical timers or electronics to control the pump run times. For example, with a 100k btu heater (average size for above ground pools), you could set your pump to turn on at 9:30 am and the water would be 8 degrees warmer when your family arrives at 5:30 pm.
 
Anyone up? Need quick help. At the eleventh hour, my husband is having second thoughts about keeping our appointment tomorrow wherein the plumber is to run the gas line for a gas heater. Long story short: the cost of running the line is $1500 (PLUS fixing drywall and ceiling of unknown amounts of damage until they get in there and look). The cost of a 400,000 btu gas heater is roughly $2000 on-line but local guy who would do warranty work and install it is $3000.00. My pool will eventually be 15 x 30 AG.

QUESTION: If we decide to go heat pump, do they get ranked (?) the same as gas heaters -- ie, would I get a 400,000 btu heat pump to get the same heatability as a 400,000 btu gas heater? Trying to do a quick calculation on up front costs. If they are the same, we might go heat pump as plumber wants to run the gas line through the house from the meter on one side of the house to the pool on the other side of the house. Will mean going through ceiling in nicely finished basement theater room and that has us (hubby especially) very very nervous that this project will not only end up costing a bunch, but be a big pain to replace drywall, paint ceiling, etc.

Help quickly if possible, as guy from gas company and plumber are coming tomorrow morning.
THANKS!
 
Why does the plumber want to run the gas line through the house? Why can't they run it around the house? Running it through the house sounds like a bad idea if they have to tear through everything. As long as the pipe is sized correctly, there shouldn't be any problem going the longer way.

I don't think that you would be able to find a heat pump that could exceed 100,000 Btu per hour under most ambient conditions.
 
He didn't exactly explain one choice over the other, except to say it would mean going around an existing retaining wall, having the potential to damage underground sprinklers, and costing more as he said they'd likely need to hand-trench. I guess maybe we'll cancel (hopefully at only a nominal fee) for tomorrow and re-examine our options. Hopefully this guy doesn't walk on us.
 
It sounds like it would be better to go around the house. You could probably get someone to dig a trench for a reasonable fee. Even if they cut a sprinkler line, it would be easy to fix, it's only plastic pipe.
 

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