I don't know the difference but I'm guessing the space heater might actually use more. Either way, I see you live in LA, I'm in So Cal as well and can't imagine running the heat right now, let alone a space heater. Both of my kids are still wearing short sleeve shirts and shorts to bed. Does the heat really need to be on? I mean, I know it cools down at night but unless we open the windows, we don't feel it, and we do sleep with the windows open right now and it still isn't cold. So, I guess, I'm probably over thinking it but someone has too LOL! How about flannel PJ's or footed jammies depending on his age and no heat, at least right now.