Heat Pump or Gas in Austin Tx

[JoyfulNoise]

I don't think anyone would be swimming if a pool heat pump had a negative COP. It takes a lot to bring even old, inefficient heat pumps to a negative COP. From what I've read, I can probably expect the heat pump at my current rental (there's no gas to my rental unit) to be around 1.5 even in the 20's °F ambient. Modern (house heating) heat pumps can maintain positive COPs to -10 °F or below. (of course this is considering a typical house at 68 °F, and pools are heated higher than that)

I have a friend here in Madison, who's considering getting rid of (natural) gas in his house and going with air source heat pumps. I did some research for him literally just now, and concluded that operating cost wise (not counting equipment, install, and maintenance costs), he'd probably break even compared with his 80% efficient gas boiler when switching to a very high efficiency air source heat pump. Yes, I did those calculations for up here in Madison, WI.

This was based on a heat pump being able to obtain an average COP of about 2.25 at an average daily temp of 20 °F (our average daily temp for January), and 2.5 at 25 °F (Dec and Feb). At a COP of 2.5, and our current prices the operating cost is a break-even between a heat pump and his 80% efficient gas boiler. So for this example, with a very high efficiency heat pump, compared to an 80% efficient gas heat here in Madison, you actually end up only paying more in January, break even in Dec and Feb, and have cheaper heating in Mar, Apr, Oct, and Nov.
View attachment 455673

Average temps here in Madison:
View attachment 455674

COP vs average daily temps from a test house in Connecticut, for a very high efficiency air-source heat pump:
View attachment 455675

Obviously this is a very high efficiency air source heat pump, and pool models are simpler, single stage fixed speed pumps. But it looks like the Raypak models get a COP of 4 at 50 °F ambient, 80 °F pool water still. At my rates (and this will vary wildly), as mentioned above, you only need a COP of 2.5 to break even in operating cost between a heat pump and an 80% efficient gas heater, which would be typical of a gas pool heater.

Now, the big thing here, besides local rates, is that a 400 kBTU gas heater can heat a pool much faster than a 120 kBTU heat pump, so you can heat as-needed much more easily, and heat loss is proportional to water temp, so shutting off between uses (like any heating application) will always save money. So for most people they'd be better off with a gas heater and heating on-demand. But for those that want a pool always ready to swim, it's probably going to be difficult to beat a heat pump.

The other thing is rates vary a lot. For pure heat component (not accounting for efficiencies), right now with my rates gas is 1/3 the cost of electric. When I calculated this a couple years ago, it was 1/5th, which changes the equation a lot.

I wonder how long until pool heat pumps start getting variable speed compressors.

I will say this about home HVAC choices - you will need to pry my forced air gas heater from my cold dead hands before I ever use a heat pump to heat a home. When we lived in a pricey coastal CA apartment community, every unit had a heat pump for heating and cooling. It worked ok in the summers but was terrible in the winters. I complained endlessly to the apartment management office about it and every time they’d send someone out and they said it was working fine. I would stroll by the unit outside on my way to throw out trash in the winter and routinely find the heat pump frozen up with frost and ice. I would send the pictures to management and they’d always reply - “our technicians say the unit is functioning properly” … hahahaha

We finally got fed up and just ran space heaters instead. Figured I was wasting just as much on electricity either way. So that was my one and only experience with heat pumps which lead me to my opinion that I will never own one. Give me NG, propane, or No. 2 fuel oil … at least those things have well defined heat contents

 

[pjt]

I wonder how long until pool heat pumps start getting variable speed compressors.

As soon as the pool equipment manufacturers can find someone dumb enough, I mean, willing enough to pay even more money than would for the regular model

I own one.

 

[JoyfulNoise]

I own one.

 

[jseyfert3]

I will say this about home HVAC choices - you will need to pry my forced air gas heater from my cold dead hands before I ever use a heat pump to heat a home. When we lived in a pricey coastal CA apartment community, every unit had a heat pump for heating and cooling. It worked ok in the summers but was terrible in the winters. I complained endlessly to the apartment management office about it and every time they’d send someone out and they said it was working fine. I would stroll by the unit outside on my way to throw out trash in the winter and routinely find the heat pump frozen up with frost and ice. I would send the pictures to management and they’d always reply - “our technicians say the unit is functioning properly” … hahahaha

We finally got fed up and just ran space heaters instead. Figured I was wasting just as much on electricity either way. So that was my one and only experience with heat pumps which lead me to my opinion that I will never own one. Give me NG, propane, or No. 2 fuel oil … at least those things have well defined heat contents

If you browse through the analysis from the NERL I linked on the heat pump home energy analysis, ice is mentioned as one issue. It wasn’t actually the coil freezing up though. It was the water from defrosting the coil, running off and freezing to the metal shroud of the unit and blocking airflow there. It could be solved with a simple heat strip stuck to the metal shroud and an ice sensor, or a better drain design (probably with a heater still for places that never see above freezing for weeks or more on end).

I mean, this was the same reason I got made at the Samsung fringe that came with the house I had until this year. The fridge was a new fancy one with it’s own evaporator. Had a resistive heater for defrost cycles. But the issue was the drain water would tend to freeze in the drain pan, plug the drain, and then it would leak the water into the fridge until it built up and leaked out of the fridge, and into the freezer compartment.

Fix was to wrap a copper wire around the heater element and stick the wire down the drain. So just bad design. They had a recall on it but they’d only sent you an aluminum piece that did the same as a piece of copper wire, and didn’t cover labor, so I just did the copper wire fix I found online.

To be fair, this house was in Connecticut. I don’t see this particular issue being an issue in coastal California, or Texas/Florida etc where with rare exceptions it doesn’t stay below freezing.

I suspect my unit won’t have that issue, since it’s an older design. The horizontal design with the coil on bottom. Probably made in 1985 or so when my unit was built…of the 6 units in my building, it appears I am the only one with an original heat pump…yay. I’m expecting it’ll be mostly electric resistive heat all winter. Like most units, it has auxiliary heat which is just resistive heater coils in the air handler.

Yours probably had that too. Switching the thermostat to emergency heat will activate the auxiliary heat and disable the outdoor unit, so essentially running space heaters for efficiency but with your air handler and thermostat still.

Not always the case auxiliary heat is electric. A coworker of mine who lives in North Carolina has a heat pump and his auxiliary heat is a gas burner. So it’s entirely possible to combine a heat pump with gas fired heat as auxiliary. Best of both worlds now. You can run the heat pump when it’s more efficient to do so, while programming your thermostat to switch entirely to gas heat when outdoor temps make it less efficient to run the heat pump. If you live somewhere cold enough where that will happen regularly, since my overall point is modern HVAC heat pumps are making huge strides in efficiency now with multi-stage or variable speed compressors.

Heck, most modern high efficiency air conditioners already have variable speed compressors. Seems unwise to NOT install a heat pump these days if you need basically any amount of heating, since a heat pump is just an air conditioner with two check valves, one additional expansion valve, maybe an accumulator, and a defrost control board and sensors, so it doesn’t add terribly much to the cost. And as stated, can probably be combined with an existing furnace or a new gas furnace for aux heat.

I own one.

What model do you own?

 

[Toxophilite]

I finally got fed up and just ran space heaters instead. Figured I was wasting just as much on electricity either way. So that was my one and only experience with heat pumps which lead me to my opinion that I will never own one. Give me NG, propane, or No. 2 fuel oil … at least those things have well defined heat contents

Efficiency wise, it's kinda a toss up decision even down here. Summer, it's just a/c as usual. Winter? We have days/weeks where the heat strips have to kick in regularly (if unit equipped) , and with the cost of electricity, who want's electric heat over gas? I wouldn't know if the whole initial cost difference, plus electrical costs, is actually any savings over an efficient vs cooling unit and an efficient gas unit, but suspect there's little gained.

 

[JoyfulNoise]

Efficiency wise, it's kinda a toss up decision even down here. Summer, it's just a/c as usual. Winter? We have days/weeks where the heat strips have to kick in regularly (if unit equipped) , and with the cost of electricity, who want's electric heat over gas? I wouldn't know if the whole initial cost difference, plus electrical costs, is actually any savings over an efficient vs cooling unit and an efficient gas unit, but suspect there's little gained.

I have no doubt that a modern, efficient heat pump would work well in my climate because of how mild our winters are but, on an equivalent energy basis, natural gas is cheaper than electricity around here. So I suspect there’s no savings to be had going either way. Seeing as how almost every home here is equipped with a gas service, choosing an efficient gas appliance brings greater simplicity to maintaining the equipment. My gas heater is stupid-simple to maintain and work on as opposed to a heat pump that would require an HVAC technician’s labor to fix. So if cheap and simple is the primary objective, a forced-air gas heater is an easy choice, at least in these parts.

 

[ajw22]

natural gas is cheaper than electricity around here.

I believe in redundancy in the critical things in life. That includes heating my house and my family. For that reason I will never live in an all electric house that is dependent on the electrical grid. I want to have dual fuels - electric and gas - to my cave. To me it is a safety decision as well as economics.

And yes I even have a wood fireplace and an axe if necessary.

 

[gkw4815]

I'd only consider a heat pump (for a pool) if I didn't have a spa or if there was no NG to the property.

If you have a spa and existing NG service, NG heater will be cheaper to buy, faster, and will allow you to use the spa in the middle of winter (which is when we enjoy ours the most!)

Regarding NG furnace benefits vs residential heat pump, I agree with the sentiments previously mentioned, and will add that during the 2021 Texas Winter Storm, we lost electricity but not NG. I was able to keep our home comfortable by powering our NG furnace with a small portable generator. Would not have been possible with a heat pump in sub-20-degree temps.

 

[JoyfulNoise]

And yes I even have a wood fireplace and an axe if necessary.

Allen in the winter -

 

[Newdude]

Y'alls are forgetting the most important factor, of the 87 other factors.

'How does *she* like to swim?'

Chances are, a July/August bathtub is preferred to a late season dip. In that case, you'll be burning 400k BTUs to do so where the heat pump would be sipping energy to do its thing.

Oh. It's electric meter reading day ? Well nothing rhymes with happy husband. Pay the man.

 

[Newdude]

* on a serious note, the needs of the pool are often different, even within the same family. We are split in my house 2 to 2 in how we'd like to use the heated pool. 2 of us want to swim now, and 2 wouldn't dream of swimming with a 60 degree breeze, no matter how warm the pool is.

 

[Toxophilite]

* on a serious note, the needs of the pool are often different, even within the same family. We are split in my house 2 to 2 in how we'd like to use the heated pool. 2 of us want to swim now, and 2 wouldn't dream of swimming with a 60 degree breeze, no matter how warm the pool is.

We are same, other than all in agreement. Ambient is as much a factor on pool enjoyment as water temp. But, we let only the visiting grandkids swim right up to hypothermia!

 

[pjt]

What model do you own?

AquaCal SQ150VS

HeatWave SuperQuiet® Variable Speed SQ150VS - AquaCal Website

The NEW HeatWave SuperQuiet® SQ145 comes equipped with all standard features. The Patented ThermoLink Titanium Heat Exchanger at its core

www.aquacal.com

 

[SJPoe]

Thank you for the information. Looks like I pay $10/mcf for natural gas. I ran this Raypak calculator online. Looks too good to be true to heat for 6 months in winter (mind you, its Texas, so doesn't get super cold) for only $2,381. Is this actually possible though? My heater is 400k BTUs and pool is 18.5k gallons.View attachment 455601

So 82 for us is a bit cool - my wife likes it closer to 87. The 5 degrees doesn't make THAT much difference (5 x 18 x 36 x 5 = 16k BTU/hour extra, 20cents an hour over what I would be paying for 82...) Once it gets much below 70 and sunny here, its just not that fun to swim...we'll jump in the hot tub instead (although the Grandson/Godson will swim if it was snowing given the chance)
Anyway...looking at their math, (usual 'failed math' disclaimer) lets say for January - 16*32*5*(82-54) = 71k btu/hour * 24hours (because even though the heaters not running, you still lose heat! Entropy is endless..) = 1.7mBTU per day, = 52MBTU = 62MCF (given 85% efficiency) at 10/MCF = $620...and they say 516....and are probably adjusting for daily solar heating - so I'm not sure they are way off base. Slap a cover on, and those numbers would probably drop in half. A cover is a couple hundred bucks - probably save that in the first month.

 

[jimbethesda]

Man, this is great info. I live in Austin, TX as well and have the same heater. My pool is 18.5k gallons with a small spa.

This will be my first winter with a pool.

When you say $1.75/hour: Do you multiply that by 24 hours to get the full day? Then times ~30 days to get the month? If so, that gets me to $1,260/mo. Or do you run it less than 24 hours a day? Thank you in advance!

We stop using our pool once the weather gets cold. We then only use the heater for the spa. How many hours a day you’ll need to run your heater to maintain your preferred temperature is highly variable depending on climate and pool characteristics. And even then, your weather is different each day. It won’t need to run much in October, but might have trouble maintaining its temp in the middle of January even with running it 24 hours a day. You’ll have to decide if it’s worth heating your pool all year round. For us, it’s not.