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I've done mostly the same (heat pumps, all electric), also in the Bay Area. In addition I upgraded the building envelope by air sealing it to high levels (1 AC
by danans 5y ago
I've done mostly the same (heat pumps, all electric), also in the Bay Area.
In addition I upgraded the building envelope by air sealing it to high levels (1 ACH50 for building science nerds - close to th the Passive House standard) and installed an always-on heat recovery ventilation system.
The net effect is that the house uses 75% fewer total BTUs for heating than it used to when I had a gas fueled furnace.
In terms of operational cost, due to the 300%+ efficiency of the heat pump used to generate those BTUs, it results in a heating cost of roughly $100 (for roughly 400kWh) for the entire winter, vs the $500 (for roughly 250 therms) that I would spend on natural gas heat.
So on an absolute operational cost basis it's not much savings, since the climate is mild, but it's wildly more comfortable and my indoor allergies are a thing of the past.
- novaleaf 5y ago> The net effect is that the house uses 75% fewer total BTUs for heating than it used to when I had a gas fueled furnace. You do realize that the 75% reduction is from your insulation improvements, not changing your furnace to a heatpump. Given the current construction/remodeling costs it's not very cost effective to insulate. It's financially "better" to just burn more heat. Yes perhaps worse for the environment longer term but most people still make decisions based on direct costs not indirect environment.
- danans 5y ago> You do realize that the 75% reduction is from your insulation improvements, not changing your furnace to a heatpump. Yes I realize that. In fact, I designed it that way to allow me to downsize the heat pump significantly. > Given the current construction/remodeling costs it's not very cost effective to insulate. It's financially "better" to just burn more heat. If you are undertaking a major home remodel that involves removing drywall, then it makes a lot of sense to upgrade the building envelope. Short of that, there are also products like blown in wall insulation and Aerobarrier that can be done without a major renovation. If you are changing the siding on your house, one should consider add a vapor permeable air barrier material to the outside. Air sealing and (re)insulating unconditioned attic floors are another cost effective way to improve the building envelope performance. Also, bear in mind that these sorts of improvements are investments in the longevity of the house, and also can create far greater comfort due to more consistent temperatures. Those things have a value also.