Wednesday, September 27, 2023


RV Electricity – Electric space heater safety, Part 1

By Mike Sokol

This is a special two-part article on a topic that’s not only seasonal, it’s very important to your safety, both in your home and your RV. This is about electric space heaters and how dangerous they can be if not used correctly.  Be sure to answer the poll at the bottom of this story where we ask about whether you do or do not use a space heater in your RV.

Just a week ago in Hagerstown, MD, (my town, in fact) there was a house fire around 3 a.m. which resulted in the death of a mother and her adult son. The fire inspector is still investigating the exact cause, but her co-workers said she used electric space heaters extensively in her house. She must have had a few close calls (small fires?) since everyone was worried about her using them to heat her house.

Are electric space heaters really dangerous? Well, don’t just take my word for it. Here’s what says about them.

Space heaters can be a quick way to heat up a room. However, they can be as dangerous as they are convenient if used improperly. Space heaters cause 25,000 home fires a year, and 6,000 emergency room visits, according to the Harvard University Environmental Health & Safety group.

Approximately one-third of all house fires nationwide happen during the cold home-heating months between December and February. Equipment that is intended to add a little extra warmth, such as space heaters, is the leading cause of these fires, according to the National Fire Protection Association (NFPE).

So, exactly what can go wrong with an electric space heater that makes them so dangerous, especially in a confined space like an RV? In Part 1, this week, I’ll discuss the issues of current draw and in Part 2, next week, we’ll delve into flammable material issues.

It’s all about the watts, and the amperage needed to make those watts happen. If you remember some of the electrical math I’ve used in the past, wattage is simply volts times amperes. That suggests we can divide the wattage of the appliance by the voltage and find out how many amps it draws.

A 1,500-watt space heater on a 120-volt outlet is 1,500/120 = 12.5 amperes. And an 1,800-watt space heater works out to 1,800/120 = 15 amperes. And while that’s a 20-amp circuit, in reality the electrical code originally designed that outlet for 15 amps of current, and assumed you would be drawing maybe 10 amps each on two separate outlets on a single 20-amp circuit breaker.

If you really do draw 15 to 20 amps continuously from an outlet, it will begin to heat up. That heating will cause the outlet contacts to oxidize and increase their resistance. And that resistance will increase the heating effect, which causes more resistance, which leads to something we engineers call cascade failure. That can result in a char around the outlet itself and a potential fire. How to know if this is happening? If the outlet your space heater is plugged into feels warm to the touch or has any dark marks around it, then the outlet contacts have been overheated and it should be replaced.

Importantly, NEVER run any electric space heater from an extension cord, especially a light-gauge one. Anything that draws 15 amps continuously needs at least a 14-gauge extension cord, and possibly a 12-gauge cord to be totally safe. That’s a really heavy extension cord for that little space heater. And never put two space heaters on a single outlet or extension cord. As you can see in my video, an overloaded extension cord can reach the boiling point of water easily.

So what can we do to avoid electrical outlet overload and heat our RVs safely with electricity? First, if you need to use any space heater at all, use it on a low-wattage setting. I think that a 1,200-watt space heater is the largest I would use on a conventional electrical outlet, and even then it shouldn’t be run unattended. And make sure your smoke detectors are operational.

Second, if you really need that much electrical heat (and it’s certainly cheaper than heating with propane you pay for yourself), then the CheapHeat product is a safe and effective solution. The CheapHeat system is specially designed to be able to run continuously as part of your RV’s furnace, and since it’s hard-wired into your circuit panel there’s no electrical outlet in the path to overheat.

So do campgrounds actually welcome the use of the CheapHeat furnace system? At first blush you may think not, since it does cost them more in their monthly electric bill compared to everyone heating with propane. However, they really DON’T like electric space heaters simply due to the risk of fire. So if you plan to heat your RV electrically, then do it correctly with a hard-wired heating system that’s designed from scratch for the job.

Join me next week for Part 2, where I’ll discuss various technologies for space heaters including coil, ceramic and oil filled. Are any of these technologies more efficient or safer than the others? Tune in next week.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit for more electrical safety tips. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.




  1. I was wondering why heating elements were not available on either of our two roof AC units so they could be used for electrical heat when 50 amp service was available. I see that the manufacturer has a heating element option for some of the units. Is their any reason why heat could not or should not be provided by a roof ac unit? They have their own fans and ducting so it would seem like a good option.

  2. Mike – I was finally able to get the kw/hr rate at the RV Park where we’ll be staying. (See my comment from Chris 11/5, above) The basic charge is $0.16 kw/hr for 246 kw/hrs/mo. It increases to $0.25 kw/hr thereafter. If we’re running it 8 hours a day, which is cheaper: propane or electric.
    Thanks a million.

  3. There are now smoke alarms that have an integrated battery in them that never need changing. The built in batteries are rated to last 10 years. Great innovation. If you can’t afford a smoke alarm, contact your fire department to see if they have a program where they can supply you with one at no charge.

  4. Update. This was in the local newspaper today. Please make sure your smoke detectors are working, both in your home and your RV. And never run a portable space heater unattended or while you’re sleeping.
    An overloaded power strip caused a fire that killed a mother and her son last month on Snyder Avenue in Hagerstown. City Fire Marshal Doug DeHaven wrote in an email that the power strip overheated and ignited combustibles in the first-floor living room. After firefighters put out the blaze, they found the bodies of Tyson Kegarise, 41, and Debra Kegarise, 62, on the second floor of the duplex at 20 Snyder Ave. “The cause of death was listed on their documents as smoke inhalation and thermal burns for both victims,” DeHaven said. Two nonfunctioning, 9-volt battery smoke alarms were found in the debris, according to DeHaven.

  5. Michael, I’ve used Patton milk house space heaters for the last two years with no problems, so far. At 1500 watts, that’s pulling 12.5 amps on a 15 amp circuit. I make sure I only have one heater on any one circuit. I constantly monitor the outlets to look for discoloration, should the connections become loose and raise the electrical resistance. Am I making a mistake?

    • On the current draw side that should be safe, as long as you also monitor the plug contacts for discoloration, the first sign of overheating. And don’t use extension cords. But the secondary hazard is flammable material in contact with the heater element itself. The NFPA guidelines call for a 3 ft area cleared of all flammable materials around any heater, but that may not be possible in an RV with limited space. However, if you can be certain of no flammable material near the heater, then it should be reasonably safe as long as it’s not being used unattended. That’s when things go wrong and fires start.

  6. We found a small tower heater that has two settings – 1500 and 750 watts. We almost exclusively use the 750 watt setting, and only use the 1500 watt setting for a short initial burst (as long as we don’t have anything else plugged into an outlet). While it doesn’t heat the entire travel trailer, it takes the extreme chill off the living area (after a while) with outside temps in the mid-30s. Sometimes using the hair dryer at the same time trips the breaker. We try to remember to turn off the heater first, but you know how that goes.

    • That’s a reasonable plan. A quick calculation of 750 watts divided by 120 volts equals 6.25 amps. That amount of current should be safe from overloading an outlet even for extended run times. Of course, an 1800 watt hair dryer draws around 15 amps on its own, so 6 plus 15 equals 21 amps of current which will trip a 20 amp breaker quickly. However, and most users don’t realize this, a thermal circuit breaker is only rated for 80% of its capacity for continuous use. So that 20 amp circuit breaker is really only able to supply 16 amps of current continuously without tripping. Even most electricians don’t realize this, but those numbers are published in every tech sheet on circuit breakers. See what I read for fun (really)…

  7. We will be staying in a RV park this winter that charges for electical use. Which is more expensive to use for heating: propane or electric?
    How significant is the difference?
    Thanks for the article. I’ll be watching for more on this.

      • Here’s the basics from an article in Home Power Magazine: Propane contains 91,547 Btu per gallon. A typical furnace will convert about 85% of that to heat, which means that 1 gallon of propane provides about as much heat as 23 kilowatt-hours of electricity. If propane costs $2.40, then electric resistance heat is cheaper if grid electricity costs 10 cents per KWH or less.

  8. The furnace never gets the front of the MH warmed up enough. My husband refuses to put a blanket over his feet (he sits in the chair in front of the door) and never knows when they are cold (has Alzheimer’s). For years we have ran an electric heater when we are home and up but I did worry about overloading the MH electrical since it is a 2000.

    I did research and bought a 14 gauge extension cord hooking it up to the 30 amp plug using the pigtail and running it through the window. I turn it off when we leave or go to bed. It runs on the lower setting but with the extension cord I could set it on the 1500 if need be. We do have a ceramic tower heater we run in the hallway pointing to our bedroom to keep the air warmer and it runs on the lower setting.

    • While this seems like a good idea at first, from an electrical code standpoint it’s a clear violation. You aren’t allowed to plug an extension cord rated for 15 amperes directly into an outlet with a 30 amp circuit breaker on it. That’s because there’s nothing to stop you from plugging TWO space heaters into a Y-cable on the end of the cord, which would easily overload the cable and cause a fire. I know that dozens of companies sell these adapters, but if an electrical inspector ever saw it he would shut you down immediately. At the very least you should probably add an outlet strip with its own 15 amp circuit breaker on the 30-amp adapter then use it to feed your 14 gauge extension cord. However, I hate to do that because that outlet strip is exposed to the elements, and any extra connection in an extension cable is one more failure point. But I really don’t have a good solution for this hookup that’s code compliant. However, you could plug this dedicated extension cord into the 20-amp outlet on the pedestal and be code legal. Is that possible for you?

  9. I use a radiant heater. It has a heating element but no fan. Using a tester I find it uses 1/2 the power of a forced fan heater which adds up to big savings in $$.

    • In next weeks column I’ll be covering the differences between coil, ceramic, oil filled and radiant heaters. Stay tuned…

  10. I use our fireplace to break the chill and occasionally leave it on the low setting for extended periods on colder nights. I believe the highest setting is 1800 watts. I hope the mfg. wired this properly per code.

    • Be aware that 1800 watts of power draw for an extended period is really dangerous since that’s around 15 amps of current which can cause overheating in a standard outlet. But many times the low setting is 600 watts which works out to 5 amps. That should be electrically safe for extended periods. Of course you still have to avoid placing flammable materials too close to the heater itself.

  11. We had a special outlet wired in our 5th wheel to the breaker panel, that is parallel to the A/C unit (on the same breaker). We either use the A/C or the heater. This outlet is marked ‘For Heater Only’. We just use the portable heater to take the chill off on cooler nights and mornings. If we need full time heat, we use the furnace.

  12. Don’t USE THEM AT ALL! I think they are incredibly dangerous, no matter if they are UL listed and approved. With the CRAPPY quality that is being manufactured in most things these days, using one of these FIRE HAZARDS is just asking for trouble.. DON’T USE THEM.

    • I can think of few things more terrifying than a fire in an RV. Videos I’ve watched show RVs being totally engulfed in flames within seconds of a fire starting. Portable electric space heaters in an RV are a really bad idea for a whole variety of reasons and should be avoided. However, if you do use an electric space heater, a lower wattage 600 watt unit with overheat protection and tip-over shutoff will be safer electrically. I’ll cover those types next week, but never run any portable space heater unattended, ever.

  13. RV Comfort Systems has successfully engineered a UL Listed RVIA compliant electric heating option. With this add-on assembly to any propane RV furnace, today’s RV’er can simply choose propane or electricity to heat the interior of the coach. Called the CheapHeat™ System, this unit is mounted directly downstream of the existing propane furnace. It employs a tungsten-heating coil powered by 120-volt 30-amp or 50-amp 120/240-volt shore power to provide the electric heat. The 12-volt DC fan motor on the furnace then pushes the heated air throughout the distribution ducting in the coach. It can be configured into three different wattage ratings, 1,800, 3,750 and 5,000 watts, depending on the shore power cord limitations. At the high heater setting (5000 watts) the system can comfortable heat a 40-foot 5th wheel down close to the single digit outdoor temps and only draws 20 amps per leg of a 50-amp service. Which leaves 30 amps per leg or 60 amps @ 120-VAC to run the rest of the RV.

    The only connection between the CheapHeat™ and the existing propane furnace is a simple wiretap on the fan motor conductor. According to CSA America (the RV Furnace certification group) it DOES NOT effect the ANSI certification of the propane furnace. You can get more information about this product at


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