So….. if the house is heated by electricity (not so uncommon in the Pacific NW and Rockies from hydro power), and you’re heating the house during the winter anyhow, whatever heat you put into the aquarium is less heat that your furnace needs to come up with, so it really doesn’t hurt you.
If you are using electricity to cool your house and using electricity to heat the aquarium…… well, that’s another story, but as long as it’s only a few degrees different, it isn’t that expensive. Trying to keep an aquarium 50 or 60 degrees higher than the ambient temperature is VERY expensive. Plants and fish at 50 degrees is pretty amazing, but even in tropical locations occasional cold snaps aren‘t that uncommon. In reality, systems are more resilient than we think sometimes.
Electric heaters are almost 100% efficient. Chillers, on the other hand, are terribly inefficient. The initial purchase price and anticipated lifetime are problems too.