haven't seen the new HP data, interesting to I assume bury the heat exchanger to use the ground?
Still, electricity comes from nukes, NG, coal, or hydro plants on the East coast, with more wind farms in the west than in the east...
The cost of electricity is typically based on price of fuel, plus distribution; they gain efficiency in bulk plants...
However, converting fuel to electricity to a mechanical force (HP works by compressing/expanding gases) to heat seems overall lots of room to lose energy- where NG concentrates all the energy right where you want it! I'll have to look into the pool specific units...
I know that furnace only homes, with no AC, are still more economical on NG, but the gap may be much narrower now than in the past!