Second - yes, significantly better communication on the website is going to help. Some economic analysis (the section of savings is ambiguous) with specifics, specifics on how it would look with financing, for different house sizes etc would get a lot of people across the hump. It's quite unclear to me if this thing makes sense financially.
Third - nice going, this really is awesome.
The unit linked in the post you're replying to states that it can operate as low as -13F.
When heating, it pulls it from the outside air. As it gets colder, there is less heat to pull out. Typically heat pumps will still keep pulling heat at >100% efficiency nearly into the negatives, but the amount they're extracting isn't enough to keep up with the heat loss of the house.
Heat lost of the house is a factor of insulation, surface area and heat gradient. It's a lot harder to keep a house at 68F when it's 5F outside than it is when it is 50F.
So when it's cold out, you need more heat generation, and there's less heat to pull from the air. That's why heat pumps have backup auxiliary heat.
You say 5f but I dont see any reference to that on your site.
I imagine anything sold in areas where it actually gets cold will as well.
Heat pumps can handle things by themselves down to around -10F to -15F, if correctly sized and installed.
Most of the low temperature ones I’ve seen include resistive heating. At some point the COP of the heat pump approaches 1.
Also, having heat to -15, then switching to no heat isn’t ideal.
If every home that could use your heat pumps year-round installed one and used it exclusively, what's the upper bound on energy saved? If every home across the country installed one and used it primarily (whenever it was warm enough outside), what would be the energy savings? Not to disparage, I'm certain it's still significant, but I'm curious to quantify it.
https://upload.wikimedia.org/wikipedia/commons/d/da/United_S...
The difference between "Can use a heat pump" and "can't" is only maybe 10º or 15º. The coldest places are only ~20% colder than much more populated areas with millions of more residents.
Metro Boston has around 5 million people -- that's more than 3x as many as who live in North Dakota and South Dakota combined. Their climate is cold and they get around 6,000 HDD every winter compared to the frigid upper plains who average something like 8,000 or 8,500. So 1.3x more heat requirement per person but spread out across 1/3 as many people.
Not to mention all of e.g. Chicago, Denver, Des Moines, Cleveland, Detroit, New York, the rest of New England, etc. etc. where heat pumps do just fine.
You can't lower the temperature across a gradient lower than the fluid temperature, no matter how fast that fluid is moving. You can cool things down faster, but you can't go lower.
So if it's 10F, a 5F heat pump will work equally well at 0mph wind and 30mph.