Makes sense (I would have guessed closer to 99% actually). But 99% is still less than both 150% and 250%:-P

You seem to assume that energy cost is the same no matter how it's delivered. Here in California, electricity is much more expensive than natural gas for the same amount of potential energy.

Yeah delivery cost might be a factor, maybe it costs more to deliver 1 kWh of electricity through a wire than (the equivalent of) 1 kWh of gas with a truck (that's what you use right?). Gas, if its stored in a big tank under your house, also had the advantage of beeing "locally cached", so you don't have to dimension the system for the max load in the same way.

Many urbanized areas in the US have natural gas distribution pipelines.

Rural areas rely on propane delivery, which is roughly 2x the cost of the piped natural gas (per unit of energy).

What is the efficiency of the power generation system? The whole system costs matter not just the individual HVAC unit