Depending on the quality of the house, of course. I mean you can find some real hovels built in the '00s of last century, and they're complete shit. But, imagine you're in an old farmhouse the probably has huge thick walls and was designed to be naturally cool in the heat of summer and warm in the winter. I joke about my bill, but my house is over 8,000 sqft, so there is a lot to heat and cool, even with comparatively modern construction.