Reality check on oil vs propane vs electric boiler
My wife and I are purchasing an old (pre-1800's) farmhouse. It's had rooms added (out and up, it looks like) along the way, of course.
Total sf is about 2100. There is old blown insulation in the attic. Not sure yet about the walls. Current heat is via oil boiler to baseboard hot water. Central AC was installed (air handler is in the attic) awhile ago. House is likely pretty leaky so the guestimate is that it'll take about 4 tons (roughly 50k BTUs) to heat the place.
We really do NOT like forced air heat. We DO like floor-based radiant heat but likely will not rip up the floors to install it at this point.
New property has a 40x60 pole building that faces SSW. I am considering having solar electric installed (about 1200 sf generating about 15 - 18 kW) which I'm told will be around $40k - $505k less 30% tax credit and $7k of PA state rebate.
So, I'm considering adding a boiler in -- either electric or propane. We can't get a gas line to the house.
Here are the unit costs I am using based on research:
Based on these calculations, I am getting costs of:
Propane: $0.0315 / 1k BTU
Oil: $0.0284 / 1k BTU
Electric: $0.0239 / 1k BTU.
I was always told that electric heat is going to be much more expensive than oil or propane, but this math is not showing this to be the case based on costs in our area.
In theory, on sunny days, it looks like the 15 kW solar system would fully run the electric boiler (50k BTU / 3400 BTU per kWh = 14.7 kWh) but of course we'd have some buy days and some sell days.
Am I missing something? This really seems like a no-brainer to me and whenever things seem that way, I get worried...