I don't really keep track of that either, but I know I spend around $60 a month on rodents for 5 snakes of different sizes. And that actually keeps me for over a month since I get the small/medium rats for my bp in a six pack from my local pet store. So even if you want to say $60 per month, that's only $720 a year. And the electricity for their heat pads is negligible really.