Gas, Propane, Oil, Mini-Splits, Electric Heat - cost per BTU?

[Charlie MacPherson]

I'm working with another BP member and we've identified what we think is a good flip opportunity.  The current heating system is propane fired FHW and the system is junk - he'll have to replace it completely.

That lead us to a discussion about which heating systems would be the most desirable. There's no piped-in natural gas available on the street, so we're down to the other alternatives.

I'm assuming that the cost-per-BTU would be the way to decide between the different options.  

Does anybody know what that cost looks like for gas (I'm assuming is the most attractive), oil, mini-splits (which can also add whole-house AC - but need backup for extreme cold), and (gasp) baseboard electric heat?