Is a Modern Cold Climate Air Source Heat Pump Cheaper to Run than Natural Gas? Maybe...
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- Опубликовано: 18 окт 2024
- It depends a lot on your situation. How well insulated your house is, your electric and gas rates, time use or not, and if you use Natural Gas or Propane. For me, its cheaper, just not all the time. I made a spreadsheet to show when it is and isnt.
As I already had a natural gas furnace with ductwork, adding the coils to the air exchanger wasn't a huge job, I had an unused 30amp breaker due to switching to gas for my dryer, and the refrigerant lines only had to run about 25 ft. We paid a little over $5k for the unit and install back in 2021, and got a $1,000 rebate from the state for having a dual fuel system. Running it in AC mode in the summer is dirt cheap, pulling barely more than 1 kW, and running it for 95 hours in August (thanks intherma for supporting my Proliphix thermostat), and figuring in 2/3 of that time on on peak, probably cost $12-$14 to keep the house comfortable that month.
My heat pump is very similar in performance at 0°F its COP is 1.78 at 47°F COP is 3.62. Mine is not a cold climate, as in it doesn't ramp up the compressor to keep the heat output steady at lower outdoor temps when to COP is low. Our Gas and electric rates are very similar. I found the balance point for me was around 12°F and that's where I would set the changeover for our gas furnace to run. I ran it like this for probably 10 years and I would recalculate it every couple years and it would be right about the same up until 2021 when gas prices went crazy.
What I ended up realizing is that the connection fee for the gas service ate up most of the savings. So I replaced the hot water heater with electric and canceled the gas service. Replaced the furnace with a blower cabinet with heat strips. Now when it gets cold, between the thermostat staging and internal logic of the blower cabinet it will stage the 2 sets of heat strips while running heat pump. So now I don't have the heatpump lockout all the way until 0°F and with the additional heat strips running as needed it keeps the house at temperature.
We don't have time of use rates here but I wish we did as that would allow me to save even more.
I think I luck out with a low gas connection fee - its only $10/mo. My gas water heater only uses about $7-10/mo (60ish showers, 4-6 clothes washings, hand washing dishes), and my gas dryer costs $3-$5/mo. I have a weird situation where the basement wall and the house aren't connected and over the course of the year shifts around and lets air in (I did have wall anchors put in years ago, but it kept moving, and because it keeps moving, it dislodges any insulation I put in the gap). This probably costs me $50-$150 a year in extra heating costs, but its hard to spent $10k to fix something that may take decades to break even.
2 years ago, nat gas was about $1.02 a Therm, a year ago $1.34, and right now is $0.65. I found an old bill from Dec 2004, and it was $1.12 back then - and that was 2004 dollars. With the crazy low gas prices right now, its hard to come ahead with the heat pump, but if they head back to the $1.25-$1.50 range, it will be much easier.
@@mattcintosh2 Our connection fee here is $16 and they approved a rate increase here in 2023 of ~4% per year until 2027. Now that I no longer have gas service I don't have access to the current rates. They have their base rates listed but there is a fuel adjustment monthly based on the purchased cost of the natural gas. My last bill for May of 2023 has it as $0.72 per therm.
Climate play a huge role in it too. We average 4600 heating degree days here with a typical low for the year of 17°F. So most of the time our outdoor temps fall right in that area where the heat pump performs well.
@@TofuInc We also have the fuel adjustment, but a lot of the time its negative. The list for mine is here www.swlp.com/CustomerService/PGARider and goes back to 2015, but that doesn't show the full story. After being higher for a few years, they get a rate increase, and then negatives happen more often, but not necessarily lower than they were before the increase. It looks like this month, instead of being -$0.42 like last month, it will be -$0.14, so instead of the $0.67 rates I was showing above, its going to be closer to $0.95 this month. That means this month the HP will be cheaper down to about 37F onpeak, and always offpeak as the PCAC (the adjustment for power) brings the electric down to $0.07, and the temps really dont get much below 20F in Oct, and usually only for a couple hours at night
Can I get some sample Kwh cost and Natural Gas costs from around the country, and the lowest temps you would see the coldest week of the year, and average temps in early Feburary? (example: Northern Wisconsin, $.12, $0.70, -15F, 25F) Places like California with $0.40 kwh costs seem to not be cheaper for a heat pump unless your nat gas therm costs are around $2.50, even when the temps only get down to 40F. The other side of that might be if you are rarely running it due to it hardly getting below 50F, then your bill will be small anyways
HSPF is only 9-10.5 for this unit, which is low for efficiency, you can get them as high as 14 in some of the smaller units, which will definitely beat gas!
@@lazerusmfh i have been unable to really find any info on units with a HSPF in ranges of 13-14. And if you live in an area that doesnt get below 30F much, i can see those being cheaper than gas. I live in an area where the daytime high may not be above freezing for a whole month. Back in the days when i just had a 80% furnace, $150 was the worst heating bill for the month, but even in the last couple years, with my 97% furnace, we had a week and a half that didnt get above 10F, and got down to almost -30F and was windy and had a $175 heating bill. My heating bill is a bit higher than in the past due to working from home, and keeping it heated all day, rather than letting it drop during the day.