So given that most gas furnaces (at least in the US) operate at 90-95% efficiency, does that mean 20 kWh of resistive electric heat (as measured on the bill) provides similar heat to ~11 kWh of gas?
Great question. When it comes to utility billing, efficiency doesn’t factor at all. Just like with electric billing, the utility company gives zero shits about what you do with your energy. They just bill you for everything you use.
Utility companies keep track of the volume used in cubic meters and convert it to kWh using the formula…
Volume (in cubic meters) • Calorific value (usually around 37-42) • 1.02264 (correction factor) ÷ 3.6 (conversion factor to kWh) = kWh
The calorific value accounts for the varying energy density of natural gas caused by its inconsistent composition. The correction factor accounts for the effects of the average temperature and pressure at the property on gas volume measurement. 1.02264 is standard for most locations but would be different if the location is extreme, like the high elevation of Machu Picchu.
What sucks about gas heating is some of the heat energy released leaves with the exhaust. The heating efficiency varies depending on the unit but is generally 90-95% for newer units but as low as 50% for older units. While 90-95% doesn’t seem bad, electric heat pumps achieve efficiencies that exceed 100%, even as high as 300+%.
This is fascinating to me. How does it factor efficiency, since gas needs to be burned?
To turn gas to electricity assume 50% efficiency. 2MWh of gas = 1MWh of electricity.
So given that most gas furnaces (at least in the US) operate at 90-95% efficiency, does that mean 20 kWh of resistive electric heat (as measured on the bill) provides similar heat to ~11 kWh of gas?
Ah. 50% efficency to turn gas into electricity.
If you are just making heat then burning gas directly is much better.
Great question. When it comes to utility billing, efficiency doesn’t factor at all. Just like with electric billing, the utility company gives zero shits about what you do with your energy. They just bill you for everything you use.
Utility companies keep track of the volume used in cubic meters and convert it to kWh using the formula…
Volume (in cubic meters) • Calorific value (usually around 37-42) • 1.02264 (correction factor) ÷ 3.6 (conversion factor to kWh) = kWh
The calorific value accounts for the varying energy density of natural gas caused by its inconsistent composition. The correction factor accounts for the effects of the average temperature and pressure at the property on gas volume measurement. 1.02264 is standard for most locations but would be different if the location is extreme, like the high elevation of Machu Picchu.
What sucks about gas heating is some of the heat energy released leaves with the exhaust. The heating efficiency varies depending on the unit but is generally 90-95% for newer units but as low as 50% for older units. While 90-95% doesn’t seem bad, electric heat pumps achieve efficiencies that exceed 100%, even as high as 300+%.