The first night after removing the pet door, we couldn’t sleep because it was so hot in the house. The next day, we burned way less wood. As it turns out, that little pet door was letting a lot of cold air in the house, and now that it’s out, we are staying warmer with much less wood.
I couldn’t find specific information about how much it costs in terms of energy to have a pet door, but judging by the staggering difference – about 10 degrees for us – in temperature by removing a pet door, I would say it could add up to a substantial amount of money in extra heating bills.
So if you have a pet door or are considering installing one, think carefully about whether or not the benefits are worth the extra expense. Our dogs are just fine being let in and out, and we don’t mind the extra effort, because the house is less drafty and we have less hassle with policing what goes in and out.