I had room to install a 1000 watt Dimplex baseboard heater. Its permanent and its out of the way. I wired it into the A/C breaker since you will never be using both AC and heat at the same time. The higher the wattage the longer they are, so I had enough room for a 1000 watt unit. They also make them I believe in 750 and 1500 watts. If you only had limited area, a 750 watt may still fit since they are shorter in length. Mine even fit under the slide out so it does not interfere with its movement. The only thing I had to do was make a deflector plate so the heat is radiated out and away. Obviously you will need ample area to mount this type of heater, but they are nice and work very well.
