But 12,000 btus isn't going to do a hell of a lot of space.
And 1.8 kilawatts isn't a hell of a lot either. What's that going to run?
Its seems its meant more as an axillary system, than a one size fits all solution.
12,000 BTUs is more than enough to heat one of those 600 sq ft R42 SIP Yurts. Might even be too hot. It all depends on how much space you have, how tight your house is, and the temperature differential you want to maintain. If your outside low is -30F then you have a different design constraint than if its 15F. Likewise it take fewer BTUs to keep a house above 50F than it does to keep it at 70.
If you have a bigger house and you primarily heat with solar air, or an in floor solar water radiant system... and this system only kicks on when those are not adequately heating the house on their own,, this can still make sense.
Electric Power is the same thing. If you aren't using it ,it runs the meter backward. If you are using it ( or more) it runs the meter forward less. In the end this system would provide about 4 months worth of electric power a year. Add it to a Solar array and its another source of power ( its very common to have a generator attached to a off-grid solar system to charge batteries when the solar output just didn't quite make it that day) Once the power is in the batteries you can draw more than 1.2Kw at any given time.
Like all green tech, most of this requires 10 years or more to ROI, and makes dubious sense at current prices. Make Coal plants go out of business and Electric power go to $1 KW ( meaning an ave electric bill of $600 month) and suddenly these things make more sense to do.