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As someone who switched four years ago to a heat pump plus conventional furnace, I can state from experience that my thermostat takes electricity cost per kWh a

As someone who switched four years ago to a heat pump plus conventional furnace, I can state from experience that my thermostat takes electricity cost per kWh and gas cost per therm (other units are available, these are just the ones that match my utility bills) and efficiency of both the heat pump and furnace and runs whichever is cheaper. Gas cost has varied a bunch over the years I’ve had it, electricity less so. But the furnace has only run a few days per year and only when when it’s been (depending on gas cost) below 10 to -5 degrees Fahrenheit. My heat pump (trane xv19) kicks ass and if I were doing the hvac upgrade again I’d skip the furnace entirely and let the heat pump work a little harder/longer on the coldest days. It’s damned near always more cost-efficient to run the heat pump. And my shiny new high efficiency furnace will never, ever pay itself off saving me a few bucks a day the three or four days per year that the math works in its favor.

solardev 3y ago
It really depends on your area's natural gas vs electricity prices, which can vary wildly. Electricity can range from 11¢/kWh to 29¢/kWh in California or higher: https://www.energybot.com/electricity-rates/ https://www.energybot.com/electricity-rates/ Natural gas ranges from (converted) ~ 2¢/kWh to 8¢/kWh in Florida: https://www.eia.gov/energyexplained/natural-gas/prices.php https://www.eia.gov/energyexplained/natural-gas/prices.php (using conversion factors from https://www.nrg.com/resources/energy-tools/energy-conversion-calculator.html https://www.nrg.com/resources/energy-tools/energy-conversion..., which I think assumes 1000 ft^3 ~= 1 therm ~= 29.3 kWh) So your heat pump's COP has to exceed the ratio between natural gas and electricity in your area to make it cost-effective (or you can get solar + battery backup). Electricity prices can vary quite a bit, too... in Cali, for example, it's gone up from 14¢ to 24¢ over 16 years, which is nearly double the rate of inflation.
throw0101b 3y ago
> As someone who switched four years ago to a heat pump plus conventional furnace, I can state from experience that my thermostat takes electricity cost per kWh and gas cost per therm […] What is the make and model of the thermostat you are using? Is it from the heat pump OEM (Trane?) or a third party?
- electric_mayhem 3y ago
  Trane xl1050. It’s a rebranded Nexia
  - throw0101b 3y ago
    "Dual Fuel Calculator" on page 15 (§5.3.8): * https://www.bayareaservice.com/wp-content/uploads/2020/02/18-HD80D1-6-EN.pdf https://www.bayareaservice.com/wp-content/uploads/2020/02/18...
voisin 3y ago
Can you give more detail about your system and in particular the thermostat that makes these adjustments? Sounds interesting!
- hazmazlaz 3y ago
  Seconded, I also want to know the model of thermostat they're using!
  - electric_mayhem 3y ago
    Heat pump is a Trane XV19 and the thermostat is an xl 1050 (supposedly trane but my understanding is it’s a rebranded Nexia) The process to update the costs (which has to be done a few times per year when my utility changes their rates) is not very user friendly - have to get into the technician menus and change scary looking stuff) but it works quite well.

solardev 3y ago

It really depends on your area's natural gas vs electricity prices, which can vary wildly. Electricity can range from 11¢/kWh to 29¢/kWh in California or higher: https://www.energybot.com/electricity-rates/ https://www.energybot.com/electricity-rates/ Natural gas ranges from (converted) ~ 2¢/kWh to 8¢/kWh in Florida: https://www.eia.gov/energyexplained/natural-gas/prices.php https://www.eia.gov/energyexplained/natural-gas/prices.php (using conversion factors from https://www.nrg.com/resources/energy-tools/energy-conversion-calculator.html https://www.nrg.com/resources/energy-tools/energy-conversion..., which I think assumes 1000 ft^3 ~= 1 therm ~= 29.3 kWh) So your heat pump's COP has to exceed the ratio between natural gas and electricity in your area to make it cost-effective (or you can get solar + battery backup). Electricity prices can vary quite a bit, too... in Cali, for example, it's gone up from 14¢ to 24¢ over 16 years, which is nearly double the rate of inflation.

throw0101b 3y ago

> As someone who switched four years ago to a heat pump plus conventional furnace, I can state from experience that my thermostat takes electricity cost per kWh and gas cost per therm […] What is the make and model of the thermostat you are using? Is it from the heat pump OEM (Trane?) or a third party?

electric_mayhem 3y ago
Trane xl1050. It’s a rebranded Nexia
- throw0101b 3y ago
  "Dual Fuel Calculator" on page 15 (§5.3.8): * https://www.bayareaservice.com/wp-content/uploads/2020/02/18-HD80D1-6-EN.pdf https://www.bayareaservice.com/wp-content/uploads/2020/02/18...

voisin 3y ago

Can you give more detail about your system and in particular the thermostat that makes these adjustments? Sounds interesting!

hazmazlaz 3y ago
Seconded, I also want to know the model of thermostat they're using!
- electric_mayhem 3y ago
  Heat pump is a Trane XV19 and the thermostat is an xl 1050 (supposedly trane but my understanding is it’s a rebranded Nexia) The process to update the costs (which has to be done a few times per year when my utility changes their rates) is not very user friendly - have to get into the technician menus and change scary looking stuff) but it works quite well.