system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does using car AC waste gas if it doesnt affect RPM?

I know that when you turn on AC another pulley in the engine needs to be powered so there is more load on the engine, but the engine doesn't have to go faster to accommodate that as far as I know? So how is more gas being burned?
gpt
You're applying an extra load on your engine. If you want to feel what an extra load does, go outside, turn on your engine and let it idle. Without touching your gas turn your wheel all the way to the right, your engine should stutter. This is because you're adding an extra load. Now it'll shutter for just a second and the rpm should drop about 50-100 rpm (not a lot) but then t evens out. That evening out is a reaction of the ecu (engine control unit) to your action. You don't feel like you're adding extra load but you are. Same with the AC. When you turn it on, you're adding an extra load however your engine wants to normalize everything and in this case it's giving it more gas and air to maintain the ideal idle.