4 ms·

Let's do some basic math: The US average cost of electricity is 16 cents / kwh [1] The US average cost of Natural Gas is $10.84 / thousand cubic feet [2] A t

Let's do some basic math: The US average cost of electricity is 16 cents / kwh [1] The US average cost of Natural Gas is $10.84 / thousand cubic feet [2] A thousand cubic feet of natural gas contains around 300 kwh of energy [3] So natural gas is around 4 cents per kwh. Gas furnaces are extremely efficient, buts lets round up to 5 cents/kwh to be conservative. So a heat pump needs to maintain a COP of 3 just to be in the same ballpark as natgas in terms of cost, and closer to a COP of 4 to be cheaper. Heat pumps "work" down to -20F or so, but the efficiency severely degrades. Heat pumps as a sole heat source are not cost competitive in cold climates. I have a heat pump in New England, and it is wonderful for 3 seasons of the year. I think all new construction should have one. But the cost to heat during winter is ridiculous. I am very glad I had an auxiliary natgas heater put in. [1] https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a https://www.eia.gov/electricity/monthly/epm_table_grapher.ph... [2] https://www.eia.gov/energyexplained/natural-gas/prices.php https://www.eia.gov/energyexplained/natural-gas/prices.php [3] https://www.eia.gov/energyexplained/units-and-calculators/ https://www.eia.gov/energyexplained/units-and-calculators/

kennywinker 4y ago
The full cost of fracked methane gas is not actually included in the price. I'm not just talking about the environmental cost: gas consumption and production is subsidized by tax dollars, and the health costs are poorly quantified but my understanding is a growing body of evidence links gas usage in the home to childhood asthma and other chronic health issues.
- dev_tty01 4y ago
  The asthma issue is with gas stoves. It is irrelevant with respect to a proper gas furnace. None of the exhaust from a modern furnace enters the home air supply. By the way, if you are going to consider environmental costs for gas you should also consider those costs for electric.
Kirby64 4y ago
One note on energy in nat gas: that assumes 100% efficient gas furnace. Cheaper furnaces are ~80% efficiency. Really good furnaces are ~95% efficiency. Adding natural gas infrastructure to a building that does not currently have any is extremely expensive, even if the natgas furnaces aren't particularly expensive themselves. I agree it's cheaper if you have it now, but that assumes you already have a gas furnace. I think the fear for most people is that natural gas can easily become substantially more expensive. European natural gas pricing is currently ~$20/mcf, and spiked to ~$80/mcf for some time. Natural gas pricing limits you to a single source for power... whereas power inherently has many sources it can come from. If natural gas becomes more expensive... you're stuck paying more with the furnace. With heat pumps, there's options available to alleviate pricing either for producers or for consumers (namely, solar for consumers). Also, importantly on the COP point: you need to talk about the area under the curve in terms of cost. Although it may be more expensive per unit of heat when COP drops below ~3, you have to think about it in terms of overall cost. A furnace will be the same efficiency if it's -50F or if it's 50F outside (for the most part...). So for the periods when it's mild, but heating is still required, the heat pump is an obvious winner. I suspect that the math works out in favor of heat pumps, even with reduced efficiency during winter, for many climates. The only thing is that you'll get a much more peaky power bill. Obviously there's exceptions, but there's vast swaths of the world where a heat pump is going to make a ton of sense.
- dahfizz 4y ago
  It sounds like you agree with me... > that assumes 100% efficient gas furnace. Cheaper furnaces are ~80% efficiency. Really good furnaces are ~95% efficiency. >> natural gas is around 4 cents per kwh. Gas furnaces are extremely efficient, buts lets round up to 5 cents/kwh to be conservative. > So for the periods when it's mild, but heating is still required, the heat pump is an obvious winner >> it is wonderful for 3 seasons of the year. I think all new construction should have one. But the cost to heat during winter is ridiculous. >> Heat pumps as a _sole_ heat source are not cost competitive in cold climates.
  - Kirby64 4y ago
    Sure, totally agree with you on that for truly cold climates. My only note would be that using natural gas as a backup/emergency source for cold climates only makes sense if you have existing gas infrastructure there... and it still makes sense to upgrade to a heat pump assuming that you don't live in a climate where it's just frozen constantly (e.g., parts of Canada, Alaska, etc) Even just routing a new gas pipe to your HVAC closet can easily be $5-10k, which would erode all potential savings during the truly cold parts of the year... not to mention the additional cost of a furnace + emergency heat wiring etc.
Dork1234 4y ago
In Eastern MA electric is 26 kwh, and $15.00 per thousand cubic feet as per January 1st. Most natural gas furnaces are between 80-90% efficient, but to get above 80% you need to have a high power electric fan. Which would put them roughly at 6 cents per kwh or (0.0625 for 80%). At COP of 3, that would mean 8.66cents per kwh, and a COP of 4 would be 6.5. Which would roughly be breaking even compared to 80% efficient furnace.
timbit42 4y ago
My electricity is 8.7 cents per kWh so that helps.

kennywinker 4y ago

The full cost of fracked methane gas is not actually included in the price. I'm not just talking about the environmental cost: gas consumption and production is subsidized by tax dollars, and the health costs are poorly quantified but my understanding is a growing body of evidence links gas usage in the home to childhood asthma and other chronic health issues.

dev_tty01 4y ago
The asthma issue is with gas stoves. It is irrelevant with respect to a proper gas furnace. None of the exhaust from a modern furnace enters the home air supply. By the way, if you are going to consider environmental costs for gas you should also consider those costs for electric.

Kirby64 4y ago

One note on energy in nat gas: that assumes 100% efficient gas furnace. Cheaper furnaces are ~80% efficiency. Really good furnaces are ~95% efficiency. Adding natural gas infrastructure to a building that does not currently have any is extremely expensive, even if the natgas furnaces aren't particularly expensive themselves. I agree it's cheaper if you have it now, but that assumes you already have a gas furnace. I think the fear for most people is that natural gas can easily become substantially more expensive. European natural gas pricing is currently ~$20/mcf, and spiked to ~$80/mcf for some time. Natural gas pricing limits you to a single source for power... whereas power inherently has many sources it can come from. If natural gas becomes more expensive... you're stuck paying more with the furnace. With heat pumps, there's options available to alleviate pricing either for producers or for consumers (namely, solar for consumers). Also, importantly on the COP point: you need to talk about the area under the curve in terms of cost. Although it may be more expensive per unit of heat when COP drops below ~3, you have to think about it in terms of overall cost. A furnace will be the same efficiency if it's -50F or if it's 50F outside (for the most part...). So for the periods when it's mild, but heating is still required, the heat pump is an obvious winner. I suspect that the math works out in favor of heat pumps, even with reduced efficiency during winter, for many climates. The only thing is that you'll get a much more peaky power bill. Obviously there's exceptions, but there's vast swaths of the world where a heat pump is going to make a ton of sense.

dahfizz 4y ago
It sounds like you agree with me... > that assumes 100% efficient gas furnace. Cheaper furnaces are ~80% efficiency. Really good furnaces are ~95% efficiency. >> natural gas is around 4 cents per kwh. Gas furnaces are extremely efficient, buts lets round up to 5 cents/kwh to be conservative. > So for the periods when it's mild, but heating is still required, the heat pump is an obvious winner >> it is wonderful for 3 seasons of the year. I think all new construction should have one. But the cost to heat during winter is ridiculous. >> Heat pumps as a _sole_ heat source are not cost competitive in cold climates.
- Kirby64 4y ago
  Sure, totally agree with you on that for truly cold climates. My only note would be that using natural gas as a backup/emergency source for cold climates only makes sense if you have existing gas infrastructure there... and it still makes sense to upgrade to a heat pump assuming that you don't live in a climate where it's just frozen constantly (e.g., parts of Canada, Alaska, etc) Even just routing a new gas pipe to your HVAC closet can easily be $5-10k, which would erode all potential savings during the truly cold parts of the year... not to mention the additional cost of a furnace + emergency heat wiring etc.

Dork1234 4y ago

In Eastern MA electric is 26 kwh, and $15.00 per thousand cubic feet as per January 1st. Most natural gas furnaces are between 80-90% efficient, but to get above 80% you need to have a high power electric fan. Which would put them roughly at 6 cents per kwh or (0.0625 for 80%). At COP of 3, that would mean 8.66cents per kwh, and a COP of 4 would be 6.5. Which would roughly be breaking even compared to 80% efficient furnace.

timbit42 4y ago

My electricity is 8.7 cents per kWh so that helps.