These are electrically powered, Servel saw the hand writhing on the wall and started making even full sized refs that had conventional compressors by the late 1940s as the gas powered ones just didn't provide enough cooling power in hot weather.
Really? I've never heard that before, didn't even know they made units with regular compressors. I've got a gas one in my garage that I have run in the summer here in Texas and it cools fine, even with a poor door gasket.