The slide-out works well, and also seals well. The panels are well insulated. Do be sure to order the double-pane glass. We set-up an electric heater on the right-hand side end-table, and point it over the bed, thereby allowing the dog to stay cool on the floor. Should we not be plugged-in, we can also use an electric blanket driven from the adjacent outlet, which is an inverter outlet.
The 1,000 watt optional inverter drives the outlets which supply the TVs, and the outlet next to the bed. It does not drive the other three remaining outlets, nor the Microwave oven. Of course, you can fire-up the generator for those, as needed.
2019 Minnie Winnie 22M on an E-450 frame