iPlug wrote: ↑
Mon Aug 05, 2019 11:46 am
Out of curiosity, have you calculated how many therms or kWh or other units of energy in coal you use annually with your forced air coal furnace?
I'll chime in since Oil-y will not have a clue
You are asking about AFUE -- the ratio of usable heat divided by heat content. In older furnaces the AFUE was ~ 55%; modern, expensive models ($4,000 - $6,000) have AFUE in the 80 -85% range.
A good heat pump costs $1,500 - $2,000 and when run wisely has a yearly COP of ~ 4. Coupled with DIY PV at two cents a kWh, one can heat or cool for a cost of ~ 0.5 cents a kWh, often without extensive ducting losses.
Coal is more complicated because the dry heat content can vary from 3.5 - 7.0 kWh a Kg, compounded by the furnace AFUE.
It can be as low as 3.5*0.6 = 2.1 kWh a Kg,
Or as much as 7*0.85 = 6 kWh a Kg
To match a heat pump fuel costs (before considering duct losses of the furnace), the low heat coal with a low efficiency furnace has to be no more expensive than 1 cent a Kg
To match a heat pump fuel costs, high heat coal with an efficient furnace and no ducting losses, the coal has to be no more expensive than 3 cents a Kg
I have no idea how much retail coal costs in NM but power plants pay 2 - 5 cents a Kg. Perhaps 2 - 3x retail ?