While converting oil to gas involves expensive remodeling, the oil to electric one can actually be done, on the margins, just by using incandescents instead of CFL, leaving lights on rather than off, putting in some space heaters, etc.

Right now, $1 buys me 54,000 BTU worth of oil. I'm not sure what the efficiency factor is for converting that to heat in the living space of the house: some goes up the chimney, some goes to heating up space and furnace equipment/piping in the basement.

On the other hand, $1 buys me 23,000 BTU worth of electricity (16 cents/kWh -- electricty is expensive here too). Efficiency of converting kWh at the meter into heat in the home is close to 100%.

So, the breakpoint is if my oil heat efficiency is 55% or higher. If less, I actually do better by generating waste heat from light bulbs and electrical appliances than by using my furnace and radiators. I gather 80-85% is typical in terms of heat kept in the home (i.e., 15% or so up the chimney), but then there's the question of whether I'm heating parts of the house I don't care about. Fortunately, small as my place is, it has zoned heat (basement and the two floors are independent).

Thanks for inspiring me to do this calculation, Tom. I'd been joking that I'm probably better off leaving the lights on than turning up the thermostat, but had thought it was nowhere near true yet. Turns out it actually is. I guess I won't stress too much about keeping lights off this winter.

As for the cost of retrofitting, I don't know. My neighborhood doesn't have gas service at all so it wouldn't be an option here (that's not uncommon in New England). From some quick googling, it seems like "several thousand" is about right -- probably more than 5 but less than 10 for most single family homes. If you wanted to go from hot water radiators to forced air that'd be a much bigger remodelling job, of course.