Tom, if you are comparing an all electric system (for example) where the source of electricity is (say) a 110v power source from the power company, then you can compare some types of performance in kW. So a resistance heater with a fan vs. without a fan for a certain space and level of heating challenges be compared. You probably can't measure comfort as objectively, but you can compare temperature at one or some average of a number of points.

I just think comparing efficiency of fuel oil burners vs. electric resistance HSBC to have some common basis of comparison. Cost per btu would be one. Otherwise, I think it is kind of apples and meat. You can compare them in terms of some criteria (cal per ounce, for example) but that's not really efficiency that your are measuring. Both are food.