Heat pumps are much more efficient than furnaces. Even if 100% of the electricity generation was coal you’d use less energy to heat your home with the pump so there’d be less emissions.
That depends on the outside air temp (OAT)*. At OATs below 30°F, the heat pump is capable to heat the home, but the coefficient of performance might be 2.0 or less.
For a fossil fuel plant that might convert fuel to electricity with ~35-40% efficiency, a heat pump with a CoP of 2.0 will be less efficient overall than a 90% gas furnace.
* More precisely, on the spread between the OAT and the indoor temp, but since the latter is basically a fixed figure...
This just isn't accurate - you use less electricity yes, but not less energy.
1 kWh of electricity run thru a resistive heater will generate 3412 BTU
1 Ccf of gas contains the equivalent energy as 29 kWh, but will only generate 8.7 kWh when run thru thermal generation (assuming 40% efficiency and 10% transmission losses).
If you're just trying to make heat, directly burning the gas will consume much less energy - and make fewer emissions - than gas > electricity > heatpump > heat.
If you're trying to compare the caloric content of two forms of energy, knowing what you can get out of the energy by itself is helpful.
In the end, the HP will be up to 30% more efficient than strip heat (in my case the crossover point is under 10f where strip heat is cheaper to operate).
I built a breakdown chart showing cost per kWh for both heat pump and strip heat, then added gas to it as a comparison.
