Hmm, well I was trying to ballpark “weighted average outdoor temperature”, specifically weighted by how much heat I’m using. Like, if outdoor temperature is only slightly cooler than what I want inside, I need relatively little heat regardless, so the efficiency of that heat isn’t all that important. My reference temperature of 30°F (~0°C) is very far from the lowest temperature we experience, it’s close to a 24-hour-average temperature during the coldest three months.
I didn’t know about HSPF, thanks for the tip! It seems to assume “climate region IV” (based on here for example), which I guess corresponds to this map which suggests that where I live (Massachusetts) is somewhat colder than climate region IV. Wiki says an electric heater is 3.41 and this says that 11.8 is about the highest HSPF out there (?), so if I divide them I get a weighted-average COP of 3.5, i.e. my initial ballpark guess was right on. But since I’m colder than “climate region IV” it would be even lower than 3.5. (To be clear, there are a bunch of things in this paragraph that I’m not sure about.)
Thanks for bringing up zoning, but we already have individually-settable radiators and do in fact keep unused rooms cold, so I don’t think that’s relevant to me personally. I’ll add a bullet point for the benefit of other readers.
I just haven’t gotten around to thinking about solar. One of these days...
Sure. For a new build in your climate zone, probably the most efficient setup is a tanked condensing natural gas water heater, ideally sorta centrally located. Then a hydronics air handler and vents that just cover the immediate area around the installation. This gives you the cost advantage of natural gas for most of the heating but you avoid the equipment cost of a second furnace. Tankless condensing is an option but in your biome there probably isn’t a sufficient advantage.
Then mini splits around the periphery for heating/cooling during most days.
Hmm, well I was trying to ballpark “weighted average outdoor temperature”, specifically weighted by how much heat I’m using. Like, if outdoor temperature is only slightly cooler than what I want inside, I need relatively little heat regardless, so the efficiency of that heat isn’t all that important. My reference temperature of 30°F (~0°C) is very far from the lowest temperature we experience, it’s close to a 24-hour-average temperature during the coldest three months.
I didn’t know about HSPF, thanks for the tip! It seems to assume “climate region IV” (based on here for example), which I guess corresponds to this map which suggests that where I live (Massachusetts) is somewhat colder than climate region IV. Wiki says an electric heater is 3.41 and this says that 11.8 is about the highest HSPF out there (?), so if I divide them I get a weighted-average COP of 3.5, i.e. my initial ballpark guess was right on. But since I’m colder than “climate region IV” it would be even lower than 3.5. (To be clear, there are a bunch of things in this paragraph that I’m not sure about.)
Thanks for bringing up zoning, but we already have individually-settable radiators and do in fact keep unused rooms cold, so I don’t think that’s relevant to me personally. I’ll add a bullet point for the benefit of other readers.
I just haven’t gotten around to thinking about solar. One of these days...
Sure. For a new build in your climate zone, probably the most efficient setup is a tanked condensing natural gas water heater, ideally sorta centrally located. Then a hydronics air handler and vents that just cover the immediate area around the installation. This gives you the cost advantage of natural gas for most of the heating but you avoid the equipment cost of a second furnace. Tankless condensing is an option but in your biome there probably isn’t a sufficient advantage.
Then mini splits around the periphery for heating/cooling during most days.