Heat Pump vs. Natural gas heater Cost Efficiency

[wgillette]

COP differences are driven by air and humidity differences. I'm assuming a month from now the pool will naturally be warmer as will the air. So BTU loss will be less, and COP will be higher.

 

[PoolStored]

COP differences are driven by air and humidity differences. I'm assuming a month from now the pool will naturally be warmer as will the air. So BTU loss will be less, and COP will be higher.

Yes, but unless your AVERAGE temperatures are 78+ degrees I'd be surprised if your losses were zero. That is a hard parameter to predict.

 

[wgillette]

Yes, but unless your AVERAGE temperatures are 78+ degrees I'd be surprised if your losses were zero. That is a hard parameter to predict.

Ah - cell formatting issue. it was set to 20%.

 

[dcsmith]

That isn't always the case, the break even is somewhere are around 5:1 $/therm:$/kwh. For me, NG is cheaper.

Mark,

I am seriously not understanding your spreadsheet calculations if what you are saying is the case.

I have plugged in the necessary information for both heaters and the results seem to indicate the heat pump wins the cost race by over 2:1 for the same amount of temperature rise. For the pool, I don't care that it takes longer than the gas heater. I am looking strictly at cost for the same temperature rise. Is this not what your spreadsheet calculates?

 

[mas985]

Maybe I wasn't clear, I was only referring to my situation which is different than yours. I was just trying to make the point that it is not the same for everyone. It depends on what you pay for both electricity and NG as well as the efficiency of the units.

 

[LapPool]

Another thought is that If you ever get solar panels, your perspective on gas might change. I considered the all-electric aspect of my house to be a negative, especially after getting a $7,500 quote for the gas company to just spend 20 minutes making the connection. Once I self-installed 15 kw of solar, I realized that all electric was the way to go. Whether solar works for you depends on a lot of factors.

 

[coolviper777]

For a Florida pool, I think a good HP is the way to go, as it's typically a relatively warm and humid area during the pool season, which I'm assuming is easily half the year there, or more. And I agree it's more cost effective than NG, especially since NG prices have risen dramatically, as least here in PA.

As other posters noted, HP suitability/cost effectivness is highly dependent on your climate. The drier the air, the less heat you can extract. The cooler the air, the less heat you can extract. You HP may not even be able to keep up with the heat loss when it's too cold.

I'm in Pittsburgh, PA. My Raypak 8450 140KBTU HP works well from early May to end of September. But once the air temps fall below 70F daytime/55 night time, the pool cools off too much at night, and it just takes forever to heat the pool (that's typically end of Sept/beginning of October). And you get less solar heating to assist late in the season in my climate.

Would love to get a 333K BTU gas heater in the future, for those early/late season warmups, with the HP for middle of the season temp maintenance when needed.

 

[dcsmith]

For a Florida pool, I think a good HP is the way to go, as it's typically a relatively warm and humid area during the pool season, which I'm assuming is easily half the year there, or more. And I agree it's more cost effective than NG, especially since NG prices have risen dramatically, as least here in PA.

As other posters noted, HP suitability/cost effectivness is highly dependent on your climate. The drier the air, the less heat you can extract. The cooler the air, the less heat you can extract. You HP may not even be able to keep up with the heat loss when it's too cold.

I'm in Pittsburgh, PA. My Raypak 8450 140KBTU HP works well from early May to end of September. But once the air temps fall below 70F daytime/55 night time, the pool cools off too much at night, and it just takes forever to heat the pool (that's typically end of Sept/beginning of October). And you get less solar heating to assist late in the season in my climate.

Would love to get a 333K BTU gas heater in the future, for those early/late season warmups, with the HP for middle of the season temp maintenance when needed.

As a test, I ran my HP several hours per day between April 5th thru the 8th to warm up the pool from 75 to 85 degrees for an Easter egg hunt for our neighborhood. The high temps for those days ranged from 86 to 92. The lows were in the upper 60s. Abnormally warm for the month of April. The additional kWh used by the HP was about 205 kWh for a total additional cost of $29.85. Our electric utility has an app that shows daily usage, so I can look at the before and after HP usage to calculate the difference. We had an immediate cool down after Easter. The first two days in May, lows in the mid 50s and highs in the low 80s. Next week looks to be getting back to normal. The pool still loses about 4 degrees overnight and is currently ranging from 72 morning to 76 late afternoon.

 

[Newdude]

Our electric utility has an app that shows daily usage, so I can look at the before and after HP usage to calculate the difference.

Do you have tier rates based on usage ? The numbers change considerably when that XX per day puts you into the next bracket at the end of the month. Then you pay taxes and surcharges on the heftier bill making it even worse.

Food for thought.

 

[dcsmith]

Do you have tier rates based on usage ? The numbers change considerably when that XX per day puts you into the next bracket at the end of the month. Then you pay taxes and surcharges on the heftier bill making it even worse.

Food for thought.

My calculations are based on generation costs - not adding in all the taxes & fees. The generation costs are fixed for the billing month. I will check on the taxes & other fees to see if they are a flat percentage or a sliding scale.