Here are the numbers for you.
A kilowatt of electricity produces 3413 BTUs of heat. It will heat at 100% efficiency.
A gal of #2 fuel oil will produce 140,000 BTUs of heat minus the inefficiency of the boiler. Say it is about 80%, then you will get about 112,000 BTUs of heat from each gal of #2 fuel oil that is usable.
So it looks like it would take 32 KWH of electricity to heat the same amount of water that could be heated with a gal of #2 oil.
@10 cents a KWH, electricity would cost you $3.20.
Not sure what you are paying for oil but @ 20 cents per KWH for electricity, your oil would have to be costing $6.40 a gal for break even.
I think you need to stay with the oil.
Jim