Propane vs. Heat Pump w/PV - SF Bay Area
I live in the SF Bay Area, but up at 2600 feet elevation, so it gets a little hotter in the summer and a little colder in the winter than down in the flats. Still, a typical winter night (like tonight) is around 40 F, only occasionally does it get down to freezing and only for a week or so. Once in the last 10 years it got down to 28 F overnight.
My 11 year old 80,000 BTU 90% efficiency Bryant furnace just cracked its heat exchanger, filling the house with CO (and triggering the CO alarm, good thing we had one of those)
So now I'm faced with the replacement decision.
Option 1: New 80,000-100,000 BTU 95% efficient furnace and a new 4-5 ton A/C unit. Furnace fueled with propane, currently paying $3.61/gallon(!) for that. We occasionally get 1-2 day power outages, and the 18 kw generator runs the furnace blower but the heat comes from propane.
Option 2: 10 HSPF heat pump, no new A/C unit required. Heat pump powered by PG&E electric E-6 time of use rates ranging from $0.09794/kwh winter off-peak baseline up to $0.32295/kwh on-peak at the 300% tier. *However* we also have a 14 kilowatt (DC rating) grid-tied PV array on the house which currently offsets 80% of the PG&E bill, keeping us pretty far down in the rate tiers. During power outages, the PV is offline so all power would come from the 18kw generator.
We also offset some of our heating load during the winter with a wood stove burning (nearly free) wood that grows on our property.
My calculations say that even at the worst case power bill, the heat pump is $31/million BTU vs $41/million BTU for the propane at today's propane prices... and of course if we're not in the highest electric tier and we're not using it during peak, the price goes down as low as $9/million BTU for the heat pump. (Even less if the PV system happens to power the whole thing of course, and I'm prepared to upsize the PV array by another 5kw if it makes sense.)
But is there more to it that would mean that I really wouldn't be happy with a heat pump, or would pay a lot more than I'm expecting (e.g., maintenance) to go that route?