Space Heaters in a fifth wheel

Yes, just be careful with them and don't exceed the amp rating of the circuit it is on.

Usually just use it when it's cool but not cold to take the chill off. If it gets cold, we the furnace takes care of it.

The short answer is yes, it's okay to use them as supplemental heat.

Whether it will be effective depends on how cold it gets. Here in the Northeast, a 1,500 watt space heater won't even begin to heat my motorhome in the winter. I have to run both furnaces to make it comfortable. And I put an electric space heater up front by the cab because the furnace design is not fabulous - I have no heat ducts in the front 10 feet of the rig. The furnaces will take the chill off up front, but the space heater fills in the gaps nicely.

I can heat my entire 5'er using space heaters only. I seldom use the loud inefficient furnace

1500 watt electric heaters work very well as supplimental heat sources. I ran one almost all of last month while camp hosting. Setting the furnace to 60 or so at night to keep from freezing. Just be careful, you likely wont be able to operate much else if the heater is running.

We very frequently use a Vornado heater as it does a great job of circulating the heat and keeping it constant with a thermostat. We don't even use the furnace until it gets below 35 or so. Of course the interior size of your unit is a factor. Space heaters cause a lot of house fires when improperly used but we even run ours all night sitting on a hard surface and completely away from flammable material. Most RVers run heaters to use the campground's electricity instead of our propane. I'm not sure they present any more danger than the furnace or water heater does.

Many people use small space heaters i their RV's. Some use a small "ceramic heater" bought at your local department store. We use a radiant heater inours. They work well to keep the unit warm.

With ours we don't use the furnace at all. The heater keeps the whole fifth wheel warm.

Personally, we don't leave the heater on when we are not there, or while out visiting friends for the evening. When get back it only takes a few minutes to warm up once the heater is turned on.