> We have two external units that serve to both heat and cool, one for each zone / floor.
All else equal, a heat pump in the Bay Area should cost about the same or slightly less to operate as a natural gas furnace during the heating season. Natural gas is 3x cheaper than electricity per unit of energy, but heat pumps run at near-optimal efficiency in the local climate. Over the heating season mine achieves an average COP of 4.0 (4 units of heat for every 1 unit of electricity input).
> Bryant is the manufacturer, if memory serves.
It's a worthwhile exercise to look up the expected maximum efficiency of your unit to see if it is achieving that.
> Even with my error, the price of electricity in California is exorbitant and the grid is easily stretched to the limit => both will be exacerbated by increased demand from EVs and housing without gas lines.
Prices for electricity are absolutely high in California compared to other states. This is for many reasons, not the least of which is the cost of natural gas itself, which sets the spot price paid for all other sources. It's also because of the utility maintenance issues brought to light by the wildfires.
However, according to PGE's own data, the average household gas bill this January is $195/month. That's on top of what people are paying for electricity. 2 years ago, it was $114/month [1]. That is a 72% increase. In the same time period, average annual natural gas only rates went up by 27%. The reason for the discrepancy is that natural gas pricing is moving toward more closely matching seasonal price variations, so much higher price/therm in the winter and lower in the summer. For 2023, winter rates will be 40% higher than summer rates, whereas in 2021 that difference was only 10%.
Therefore today, you would probably be paying more to heat the same house with a natural gas furnace than with a heat pump. The vast majority of people who use natural gas for heating are discovering that reality right now.
Furthermore, there's not much of a future in which natural gas gets cheaper as an energy source during the heating season. That's just the reality of that energy source.
Meanwhile, peak electricity rates have increased 22% since 2021 (when peak rates were $0.40/kWh), but the seasonal variations in electricity demand are currently the opposite of natural gas (lowest in winter, highest in summer).
In the long term, we can expect winter electricity demand to rise as more heat pumps are deployed. However, even if we exclusively burned natural gas (which we won't) to generate the electricity to meet that demand, it makes far more sense to do so in a combined cycle plant that is 50-60% efficient and sending it to heat pumps getting 3-4 COP, yielding a 200%+ "efficiency", than to burn it in furnaces that achieve on average 80% efficiency.
1. https://www.pge.com/tariffs/Residential.pdf