Climate

In many areas, fossil fuel energy is much cheaper than electrical energy, so much so that even with heat pumps operating at 300+% efficiency, it was still cheaper to burn fuel than to use a heat pump.

When piped residential gas cost $0.01/cubic foot, and each cubic foot contains 0.3 kWh of energy, that energy price was comparable to 3.3 cents per kWh. So even compared with a electric heat pump that was 300% efficient, that gas would still be cheaper than electricity that cost $0.10/kWh.

Now that gas is more expensive (national average approaching $0.02 per cubic foot), and heat pumps tend to be more efficient, some up to 500%, the simple math starts to favor electric heat pumps, where a 500% efficient heat pump running at even $0.30/kWh is still cheaper than a gas furnace. Basically, the breakeven point has tripled in just over a decade.

Also, as heat pump technology has improved, they are capable of operating efficiently at lower temperatures than before, so that the real world performance more closely matches the simple calculations in those cold climates. Plus because they work better now, the customers are less likely to notice a performance difference in heating.