If it is not all that cold where you are then one of the small "personal" ceramic heater might be enough for comfort. Go to Walmart of a similar store and look for one of these small "personal" ceramic heaters. Many of these types of personal heaters don't have a cord on them, them plug directly into a wall socket or in your case an inverter. Be sure your setup is very stable so the heater will stay in an upright position with no possibility of it falling over. On the heaters that plug directly into a wall outlet there is not going to be a safety tip over feature. But there are some very small personal ceramic heaters that run at 200 watts that have a cord on them. The personal sized ceramic heaters range in size from 200 watts up to about 600 watts. They are not meant for heating larger rooms, only small areas.
Make sure the inverter you use is rated for more watts than the heater.
I have one that is 350 watts. It is enough to keep my small, insulated, travel trailer nice and comfy in cooler but not freezing temperatures. It says it will heat 150 square foot room, but it would certainly not raise the temperature up to 60 degrees inside if it was freezing or below outside. In an RV we have cold all around us on every side. That is different than in a house where you have other rooms buffering you from the outside chill factors.
Look for one with a digital thermostat that can set to maintain the temperature you want for the space. Also look for one that includes a timer on it. These personal heaters have a small computer type fan in them to distribute the heat, it is a very quiet fan, it won't keep you awake. Because it very quiet you might forget it is on which is why the timer is a good backup just in case you forget to turn the heater off.
The 350 watt heater I own is small enough in power consumption to run off of my 1000i Honda Generator and still have power left over for other things such as topping off my battery or using the computer.
