Electric Spa Heater for Spillover Spa?

[CJadamec]

There are too many variables to say what it will take to maintain. I would figure less than 15 min of burner time an hour as a median time. That's just to maintain with a cover on. Also depends on the size of the unit. I would also put a 250 gallon tank or 2 100's because of the vapor pressure issue associated with propane. Again that really depends on the size of the heater. At 4.60 a gallon that is going to be really costly. For the cost of your propane a heat pump will heat you whole pool monthly.

Otherwise the prices and terms that company gave sound reasonable and normal.

 

[wsamon]

I don't think we're going to keep it heated 24/7, at least not with propane. That doesn't sound reasonable for us budget wise. I'm more interested in what it takes to keep it at the 100 deg temperature for an hour or two with a couple people in the spa and obviously no cover. That will allow me to do some basic calculations for the expected cost for each use. I think our standard usage is probably going to be starting with 75-85 deg water (depending on time of year), getting it up to about 100 and then maintaining it at 100 for up to 2 hours or so before turning it off and putting the cover back on. So in the 2 hours of usage once the spa's already at 100 or so, about how many BTUs should be required to maintain that temperature?

BTW, I want to thank everyone for all the awesome information. You have all already done more than enough to help me out and I really appreciate it.

 

[CJadamec]

I was guessing​ you were going to use about 20 gallons a month in propane. That was based on about 3 days a week of usage. 20x4.60= 92.00 a month in propane.

For that much money in propane per month a heat pump can keep you pool warm (around 85) and heat your spa when you want to use it for the same 92 a month or less.

 

[wsamon]

I was guessing​ you were going to use about 20 gallons a month in propane. That was based on about 3 days a week of usage. 20x4.60= 92.00 a month in propane.

For that much money in propane per month a heat pump can keep you pool warm (around 85) and heat your spa when you want to use it for the same 92 a month or less.

That's definitely worth considering. I'll have to run the numbers, but it seems much more expensive up front, and how quickly will it get the spa temperature up to 100? Also, I don't think it'll take 20 gallons from what I've seen. It looks like it should take about 1/2 gallon to raise the 200 gallon spa from 80 to 100, and I assume it wouldn't take much more than another 1/2 gallon just to maintain the temperature for a couple hours. That would knock the consumption down closer to 13 gallons per month. Also the $4.60 is the highest price quoted to me. They said it ranges from $2 to $4.60 or so.

The reasons I'm considering the gas if the small electric one doesn't work out are: lower up front purchase price, presumably lower installation fees since there's already a propane heater hooked up to all the necessary pipes (we may even be able to install it ourselves), and much more power / quicker heating. Also, buying used seems both easier and safer (less likely to have an expensive part needing repair quickly) with the gas? I'm really not sure about that statement but it seems to be the case right now.

From my admittedly rough/poor calculations using Spa Heater Sizing Calculator | Jandy Pro Series I estimate using 1 gallon of propane per spa session (.5 gallon to get up to temp and another .5 gallon to maintain the temp for 1-2 hours). Even for purchases in the high season @ $4.60 / gallon that comes to about $62 / month. During the low season @ $2.50 / gallon that's more like $35 / month. Additionally, the 350k BTU should only take about 5 minutes to get the water from 80 to 100. Of course, as a negative it also requires an unsightly and potentially dangerous propane tank.

If I have to go new, from what I see, it would look something like:
(sorry for all the junk below, I'm actually figuring this out as I write this post )

Propane
$1850 for 350k BTU heater
$500 for propane installation (including 1 fill)
I'll need to fill about twice per year, so that's another $40 / year ($20 for year 1), and the tank lease after year 1 is $96

Up front purchase / installation cost: $2350
Year 1 operating cost at max rate (remember one full tank is included) ~= 70 gal * $4.60 + $20 =  $342
                              at min rate ~= 70 gal * $2.50 + $20 = $195
                              average rate ~= 70 gal * $3.55 + $20 = $269
Year 2+ operating cost at max rate = 156 gal * $4.60 + $40 + $96 = $854
                              at min rate ~= 156 gal * $2.50 + $40 + $96 = $526
                              average rate ~= 156 gal * $3.55 + $40 + $96 = $690 (~$58 / mo)

So, over 5 years I should be looking at about $2350 + $269 + 4 * $690 = $5379 or about $90 per month after which includes purchase and installation

Alternatively, I could purchase a tank for about $700, which would save me the tank rental fee, about $1 / gallon on price, and also let me shop around for other propane distributors. That would give:

Up front purchase / installation cost: $3050 (assuming installation costs remain the same using my own tank)
Year 1 operating cost at average rate ~= 70 gal * $2.55 + $20 ~= $200
Year 2+ operating cost at average rate ~= 156 gal * $2.55 + $40 ~= $438

So, over 5 years I'd be looking at about $3050 + $200 + 4 * $438 = $5002 or about $83 / mo including purchase and installation


Heat Pump
$3150 for 140k BTU heater
$700 for installation? (websites claim $500 - $1000, I'm hoping my sub panel has enough juice and eases this considerably, but it may need a concrete pad and be substantially bigger than my current heater, requiring some replumbing to make room)
Ongoing expense is really just the electricity, which I'm having a difficult time estimating and/or finding any calculators online. This heat pump uses 7.5 kw, for which we pay $0.125 / kwh and has a COP of 5.75. If anyone can help out here, that would be great. In theory the 140k BTUs should raise the spa from 80 to 100 in about 20 minutes. Like above, I'm assuming it would take that again to maintain the temperature for 1-2 hours, so 40 min of run time per swim? Of course, I don't know if any of this is factoring in the in-ground heat dissipation issue.

Up front purchase / installation cost: $3850
Monthly heating cost maybe $10 for just the spa?
Heating cost using CJademic's estimate (for the whole pool): 12 * $90 = $1080
Heating cost using my bad estimate (for the spa only): 12 * $10 = $120

To compare apples to apples, if we do just the spa over 5 years I'd be looking at about $3850 + 4 * $120 = $4330 or about $72 / month


So you're right, if I do have to go new, the heat pump is looking like a better option assuming there's nothing that would cause an exceedingly expensive install. Unfortunately, both options pretty much blow our budget out of the water, so I don't know if either is doable . At this point it really may depend on whether or not the smaller $500 spa heaters will work (the company to respond to my Angies List inquiries stated they don't do heater installs w/out a bigger build... I guess I'll have to waste an afternoon calling...) or if I can find something decent on CL. I've seen some OK looking 250k propanes for $800 or so and a reconditioned Gulfstream (never heard of them) 113k BTU heat pump for $1150 that supposedly comes with a 6 month warranty...

 

[ps0303]

You have a pool/spa combo with a spillover correct? So do you have a separate circulation pump for the spa if you think you are going to heat the spa and put a cover over it when done? Also do you have a valve that you can stop the spill over when you have the system in pool mode? Maybe you already covered this in your previous posts.

It just doesn't seem reasonable in my mind working in the industry trying to do what you want. I have heard nothing but complaints from people with a heat pump on a spa when they want to use the spa in the cooler months here in FL. The most efficient way to heat a spa is with gas, either propane or natural. Trying to come up with an out of the box way to get heat has been done by many and it was not very efficient.

If you really wanted a heater for the spa then go to Pinch A Penny and finance a gas unit. Buy your own propane tank and then shop for gas.

I'm just telling you as an industry professional the correct way to do this.

 

[wsamon]

You have a pool/spa combo with a spillover correct? So do you have a separate circulation pump for the spa if you think you are going to heat the spa and put a cover over it when done? Also do you have a valve that you can stop the spill over when you have the system in pool mode? Maybe you already covered this in your previous posts.

It just doesn't seem reasonable in my mind working in the industry trying to do what you want. I have heard nothing but complaints from people with a heat pump on a spa when they want to use the spa in the cooler months here in FL. The most efficient way to heat a spa is with gas, either propane or natural. Trying to come up with an out of the box way to get heat has been done by many and it was not very efficient.

If you really wanted a heater for the spa then go to Pinch A Penny and finance a gas unit. Buy your own propane tank and then shop for gas.

I'm just telling you as an industry professional the correct way to do this.

I do not have a separate pump for the spa. However, I often maintain it below spillover levels and have had no more difficulty with the filtration or chemical balance than with my normal pool. I do make sure to run the pool in spa only mode (or sometimes spillover mode) frequently enough that it gets filtered and remains clear. I don't plan on maintaining the spa water at spa like temperatures 24/7, just regular pool temperatures plus the solar cover which heats it up more than the pool due to being a smaller, shallower body of water. I'm estimating it will maintain about 85 during the summer and maybe 70 during the winter. If I got a full-size heat pump I would consider maintaining the entire pool's temperature somewhere around 82-85 which would allow me to use the spillover feature without sacrificing the water temperature too much.

I have valves that allow me to enable/disable the intakes and returns of both the pool and spa individually. This includes the pool skimmer, pool main drain, pool cleaner, spa main drain, pool returns, and spa returns. So if I want it to only circulate the pool water, or only circulate the spa water, or suck from the pool and return to the spa, or suck from the spa and return to the pool, or any combination, I can do so. This makes it pretty simple to maintain the water in the spa at a level that it never spills over when in either spa or pool mode.

I very much appreciate your response and will seriously take it into consideration, especially since it's coming from experience and not just theorizing. However, I'd like a little clarification on some of the details if you don't mind.

• What kind of heat pumps are you talking about with the unhappy customers? The electric spa heaters or the real heat pumps designed for the whole pool? What BTU ratings?
  • The spa ones are designed for spas even bigger than mine, and I haven't seen anything that mentions excluding in-ground spas. They also seem to have a lot of good reviews online, including people that use them to heat 15k gallon pools. Considering my spa is only 200 gallons I assume that it can heat the thing up from 80 to 100 even if it takes 40-60 minutes.
  • The heat pumps I'm looking at have higher BTUs than some of the smaller propane pool heaters, so I'd think they could provide enough heat. Otherwise those smaller propane units are basically worthless.
• What do you consider the cooler months in FL? If we can't use the spa during Dec, Jan, and Feb it wouldn't be ideal but we'd be OK with it.

I do understand that I may not be doing it the "right way", but we just can't afford to drop the $3k - $4k+ right now. So what I'm doing is lowering my expectations in return for a lower price, not trying to "beat the system". As for financing, Amazon would actually be better (much lower prices + 0% interest for 1 year), but we're trying to pay off revolving debt, not add to it. So I'm trying to find a way to at least get spa-like temperatures for the next couple years so that my wife can use it to relax after taking care of two < 2 year olds all day. It's something she's wanted since we bought the house a couple years ago and would make a good anniversary present. That said, if it's not going to work, it's not going to work and I don't want to waste our money.

 

[CJadamec]

In general heat pumps don't work well when ambient air temps are below 60. They will still work but the less heat in the air the less heat they can take from it.

ps0303 isn't wrong that a propane heater will do your spa the quickest. You also know that owning your own tank saves money on gas but also costs money to buy.

Your spa\pool set up is fine with the single pump as you said before because you can circulate the spa by itself without the spillover. You are also aware you will need to use the spillover to keep the water in the spa treated and clean.

If your main priority is the spa and the pool temp is take it or leave it go with the gas option and you will be happy.

If having both pool and spa warm is what you want then the heat pump is the more economical option in the long run. You've armed yourself with a lot of info and that's the best thing you can do. You know your budget better than any of us and the last thing anyone here wants you to do is waste hard earned money on something that won't work.

 

[wsamon]

In general heat pumps don't work well when ambient air temps are below 60. They will still work but the less heat in the air the less heat they can take from it.

ps0303 isn't wrong that a propane heater will do your spa the quickest. You also know that owning your own tank saves money on gas but also costs money to buy.

Your spa\pool set up is fine with the single pump as you said before because you can circulate the spa by itself without the spillover. You are also aware you will need to use the spillover to keep the water in the spa treated and clean.

If your main priority is the spa and the pool temp is take it or leave it go with the gas option and you will be happy.

If having both pool and spa warm is what you want then the heat pump is the more economical option in the long run. You've armed yourself with a lot of info and that's the best thing you can do. You know your budget better than any of us and the last thing anyone here wants you to do is waste hard earned money on something that won't work.

I know, and I appreciate all the information everyone's provided. I don't want to be wasting your guys time either by begging for more information or trying to get you to make a decision for me, but it seems like people keep adding something that seems somewhat different / contradictory to what I've heard from others So it's hard to get the facts straight.

Where I live in the Tampa Bay area, the temperatures really only get below 60 at night during January and maybe the end of December and beginning of February. It only goes below 60 during the day for about 1 week or so each January, so it seems like a heat pump should work fine for the vast majority of the year, which was my understanding, but that's contradictory to what the previous poster said, unless he was just referencing the 11kw 37k BTU heater I originally asked about.

I learned a lot from this thread, hopefully others will too. As stated several times, I'm willing to make sacrifices on heating times for the spa, so long as it stays around an hour (preferably less), as well as lose the ability to heat the pool if it means significant cost savings due to our budget. That's why I asked about the spa specific heater originally. However, no one seems to be able to verify the spa heater's effectiveness / times one way or the other, which has me concerned about going that route.

Here's a simplified table of my findings in case it helps others or if anyone wants to correct my view

Type	Startup Cost	Yearly Cost for Spa	Mins Heat 200 gal 20 deg	Notes
350k BTU Propane w/ owned tank	$3100	$450	7	Operating costs could fluctuate wildly. Could heat entire pool but would be very expensive (~$80-100 to heat 10 degrees one time). Requires above ground propane tank in yard (buried is $2k+).
140k BTU Heat Pump	$3900	$140	20	Could heat entire pool for ~$90 / month. May not be effective during Dec, Jan, Feb
37k BTU Spa Heater	$1000	$701	100	Can not heat pool

Calculations used for electric are 7.5 kw for heat pump, 11 kw for spa heater, $0.125 / kwh, and using the same amount of electricity to maintain the temperature at 100 for 2 hours of use as it takes to raise it to 100 from 80 (therefore the spa heater runs much longer and costs more / hour).

In this model, if used just for the spa, the heat pump becomes cheaper than the propane starting in year 4, and cheaper than the spa heater in year 6

Update: I got information from a user on Amazon that claims the spa heater raises their built-in spa 35 degrees in 3 hours. If this is true then it should take about an hour 40 to raise it 20 degrees. I did mention the size of my spa in the question and they claimed they had the "same situation" so hopefully their size is comparable.

 

[wsamon]

One last question: In the example of heating a pool / spa, are BTUs BTUs no matter how you get them, or are there further differences between heat pumps and propane in this regard? (not counting the drop in BTUs for heat pumps due to ambient temperature / humidity).

If I had a 140k BTU heat pump, would it heat the water as quickly as a 140k BTU propane heater and faster than a 110k BTU propane heater? Or is there a ramp-up time to get to the 140k BTU production, or some other factor with the electric that would cause it to take longer?

 

[CJadamec]

A BTU is a standard measurement. 1 BTU will heat 1 pound of water 1 degree F. There are 8.34 pounds of water in each gallon. It doesn't matter what the source is 1 BTU is the same whether it comes from gas, electricity, fuel oil, gasoline, a wood stove, or the sun.

 

[pooldv]

Yes, all BTUs are created equal. 1 BTU will heat 1 pound of water 1 degree and pool heaters are rated based on how many BTUs they provide per hour. So you can do the math, as I did above, to calculate how much or how long a particular sized heater will take to heat a body of water. What needs to be estimated or calculated is heater efficiency and heat loss over time.

Another fact is that it will take the same number of BTUs to heat your water from X temp to Y temp no matter what heater you use. A bigger heater will just do it faster, it won't cost more. A 200k btu will heat your spa twice as fast as a 100k btu heater but the energy cost will be the same.

 

[wsamon]

Yes, all BTUs are created equal. 1 BTU will heat 1 pound of water 1 degree and pool heaters are rated based on how many BTUs they provide per hour. So you can do the math, as I did above, to calculate how much or how long a particular sized heater will take to heat a body of water. What needs to be estimated or calculated is heater efficiency and heat loss over time.

Another fact is that it will take the same number of BTUs to heat your water from X temp to Y temp no matter what heater you use. A bigger heater will just do it faster, it won't cost more. A 200k btu will heat your spa twice as fast as a 100k btu heater but the energy cost will be the same.

So no significant ramp up time to get the heat pump "up to speed." That's what I figured but wanted confirmed since most people claim that the propane heats quicker, pretty much unconditionally. But you can actually buy a heat pump that produces more BTUs than some propane heaters (140k BTU heat pump vs 110k BTU propane heater for example).

I knew about the speed / cost thing, but thank you for pointing that out

 

[pooldv]

That is correct, a 140k btu heat pump will heat your water faster than a 110k btu propane heater. When I turn on my heat pump the water coming from the returns is instantly hotter.

People say gas heaters heat faster because most folks have a 250k or 400k btu gas heater vs most folks with a 90k-140k btu heat pump.

 

[wsamon]

A BTU is a standard measurement. 1 BTU will heat 1 pound of water 1 degree F. There are 8.34 pounds of water in each gallon. It doesn't matter what the source is 1 BTU is the same whether it comes from gas, electricity, fuel oil, gasoline, a wood stove, or the sun.

lol I know I sounded like an idiot with that question. I didn't literally mean "are BTUs different depending on the device". That'd be like asking "are inches different when measuring a floor vs a table?" lol. I meant are there other factors to consider that are inherent in the technology that would affect the heating times, such as: burning propane goes from 0 BTUs to 300k BTUs instantly because once the flame's there, it's there; while a heat pump takes 10 minutes to slowly climb from 0 to 140k BTUs as it heats its metallic elements with electricity.

 

[pooldv]

LOL!!! No, tables and floors are always the same. But, if you switch from a tape measure to a yardstick you need to make some adjustments.

 

[wsamon]

LOL!!! No, tables and floors are always the same. But, if you switch from a tape measure to a yardstick you need to make some adjustments.

true true. Tape measures are metal and yardsticks are wood. Everyone knows that when inches were defined they weren't using metal to take measurements yet so they're only calibrated for wood and you need to adjust for the difference in materials when measuring items longer than a foot or so...

 

[CJadamec]

I think pooldv nailed it on the head. The perception that gas is hotter is because you are comparing a 300k+ heater to one doing around 100k. I too have never noticed any lag time between the heat pump coming on and the water getting hot. You are using the pool water to cool of the refrigerant gas coming off of the compressor. As soon as that compressor starts that gas heats up very quickly.

 

[ps0303]

But what you do notice is that gas heats quicker than a heat pump. And when it's cooler outside, it takes a heat pump longer to heat. So either you wait 15 minutes or an hour. That's up to you. I sure as heck am not going to wait an hour for the spa to get hot.