How Does An RV Use Electricity From A Battery?
All RVs, travel trailers, 5th-wheels, and truck campers can run off of external power from an outlet, whether it’s 50, 30, or 20 amp. But they can also run off of 12 volt power which comes from the batteries located somewhere inside or outside. When using 12 volt power only the appliances that are 12V compatible will work.
Because RVs use 12V power you need to make sure your batteries have a voltage of 12. If you are going to use 6V batteries or more than one 12V battery, you need to wire them in a specific way to keep the voltage correct. For more information on that check out this article on how to wire multiple batteries to an RV here.
What Will The RV Battery Run?
If you’ve ever dry camped/boondocked you’ve probably noticed that certain things aren’t working in your RV that normally would.
For instance, the air conditioner, wall outlets, microwave, and TV won’t work. (There is such thing as a 12V TV and if your RV has one of those it should be able to run off the battery)
You can get things like the wall outlets, the TV, the microwave, and even the air conditioner to run using things like generators. They make smaller generators like these, that can charge your RV batteries, run the TV, and the wall outlets. If you want to run the AC while dry camping you can even get a large generator like these.
We boondock 90% of the time and we do own a small inverter generator for emergencies but we mostly use the Yeti 1000 (click to view on Amazon) which is an electric power station we plug our trailer into and charge with solar panels. We can even run our small microwave with it.
So, what should be working in your RV when not connected to electricity? I’ll go through each thing and include the wattage used as well as ideas and ways to save power if possible.
The first and most noticeable thing that the RV battery will run is the lights. Light is a necessity when camping and your lights will work whether you are plugged into power or not. Most RV lights are small and you would think they don’t use much power and won’t drain too much power from your RV batteries but in a lot of cases that isn’t true.
Unless your RV is only a few years old it probably uses traditional incandescent light bulbs like these Camco’s (click to view on Amazon). The problem with this kind of 12V light bulb is they aren’t very bright, and they use a lot more power than you would think. A 12V incandescent light bulb is going to use 10-12 watts of power per bulb. It doesn’t sound like much until you have a bunch of them on to light your RV at night.
Your light bulbs alone could be drawing around 120 watts an hour just by being on. If you got your batteries from an RV dealer or haven’t bought high capacity ones you may only have around 600 usable watt hours or even less. That means your lights will drain your batteries in just 5 hours.
One way you can greatly reduce the power draw of your RVs light bulbs is to replace them with LED ones. LED lights are not only brighter, longer lasting, and safer for RV use, they also use only 1/3 of the power. The average LED RV light bulb will only use around 3-4 watts of power. In a lot of cases, you may only need to use one to replace two incandescent RV light bulbs because they are so much brighter.
When it comes to LED RV light bulbs you get what you pay for. I’ve heard countless people talk about their LED bulbs only lasting for a few months before needing to be replaced. We use SRRB RV LED Lights (click to view on Amazon) in our own trailer and after 8 months of full-timing they are still going strong and none have needed replacement.
To compare them with the older kind of RV light bulb, 10 incandescent will use around 120 watts an hour, 10 LED bulbs will use at the most 40 watts an hour. That’s 1/3 the power usage and an easy way to make your RV batteries last longer when dry camping.
The second most important thing you need to use in your RV is water. The water pump is only going to use power when it’s running and even if you are going to take a shower the watts used aren’t going to be very high. The difference between the watt or amp usage between different kinds of 12V RV water pumps is ver low and changing one out for a smaller or more energy-efficient one isn’t going to save you very much power.
The Shurflo 12V RV Fresh Water Pump is one of the most powerful water pumps you can get for an RV. It has a flow of 3.5 gallons per minute and uses 7 max amps. That’s 84 watts an hour when running. Chances are your RV is using an even smaller pump than this one which means even less of a power draw.
You can save on power by limiting your water usage by not taking as many showers when dry camping/boondocking and using a pitcher of water for drinking water so you don’t have to run the water pump every time you’re thirsty.
The stove in any RV has a hood over it that will normally have a light and a fan in it. The light bulb is going to be a source of power draw as most RV 12V hoods usually have a high wattage incandescent light bulb in them. The good news is you can usually replace these with the same LED light bulb that goes in the standard light fixtures in the RV.
The fan uses power as well, but it won’t be much no matter what size of range hood you have. For instance, the fan in the range hood of my travel trailer only uses around 20 watts an hour.
RVs will have a wide range of bathroom fan sizes. If you have the kind of vent with a small fan that takes up about 1/4 of the vent space then it will draw anywhere from 12-24 watts an hour when in use.
If your RV has a large bathroom fan like the Maxxair MaxxFan (click to view on Amazon) or a Fan-Tastic Vent RV Fan (click to view on Amazon) then you can expect a power draw of anywhere between 20-60 watts depending on how high the fan is set at.
If you use the RV fan to keep air moving and cool the RV remember that power is being used and the fan will be slowing draining the RV battery.
One amazing thing about RV refrigerators is they can run on LP gas (propane) when not connected to electricity. When you are connected to shore power you can switch the fridge over to the auto setting and the fridge will use only electrical to run but when using 12V power the RV fridge has to run on gas.
Even when switched to gas the RV fridge is going to use some 12V electricity to run the thermometer and electrical starter. On average an RV fridge will use around 240 watts a day when on the gas setting. That’s only 10 watts an hour but since the fridge has to run 24/7 there will be some drain to your RV batteries and there’s not much you can do about it.
RV Water Heater
All RV water heaters with a tank have an electrical and a propane option to heat the water. When running on propane expect the water heater to use a tiny bit of electricity to run the thermometer and electric starter.
The furnace in an RV uses propane to create heat but there is also a fan that blows that heat into the RV. Different sizes of RVs use different sizes of furnaces that draw different amounts of power from the RV battery. No matter what size of furnace you have there is going to be a lot of power being drained from the batteries when not connected to electricity. That’s why you can only run the furnace for a few hours when dry camping/boondocking and you have to keep an eye on your batteries so they don’t go below a safe discharge level.
For more information on how long you can run the furnace with RV batteries check out this article here.
RV Propane Alarm
Every RV has to have a propane alarm in case there is a gas leak. Gas leaks are extremely dangerous and you should check your propane alarm regularly to make sure it’s working. Most RV propane alarms are wired to the RV batteries and use 12V power. You should never let your RV batteries go completely dead because you want the gas alarm to be working at all times.
A modern RV propane alarm should only be using around 1-2 amps of power a day, that’s a max of 24 watts a day which is around 1 watt an hour. It’s not much of a power draw but it’s still something that will slowly drain an RV battery over time. That’s why you should remove your RV batteries when winterizing your RV because there are things like that RV propane alarm that will kill the batteries over the winter.
The RV radio and speakers are going to draw some power from the RV batteries when running. The amount of power draw is going to depend on how many speakers your RV has and how many you are using. Many RVs have the option to use outside speakers, inside speakers, or all the speakers at the same time.
The speaker’s quality, size, and kind will change the amount of power used. Some larger outdoor RV speakers will use as much as 100 watts each while smaller inside speakers will use only 50 watts each. Either way, the power usage adds up and it’s something to think about when you are dry camping and trying to save on power.
TV Antenna Booster
A lot of times the RV TV antenna can be boosted using electricity. This is normally something you can turn on and off as needed. When turned on a red light will be shining. A traditional RV antenna will use around 12 watts an hour.
If you accidentally leave the booster on that’s power being drawn from the RV batteries all the time so make sure you only use it when you need it and you make sure it gets turned off when you’re done using the antenna.
Slide & Jacks
If your RV has a slide it’s going to be powered by the RV batteries if you don’t have the RV engine on or the truck plugged in. It’s hard to say exactly how much power the slide-out motor uses because there are so many different sizes of slide-outs that use different strengths of motors. To give you a basic idea a slide-out motor is usually between 30-40 amps which means the watts drawn from the 12V battery will be anywhere from 360-480 watts.
Even if the slide motor only runs for a few minutes that’s going to be a high power draw from the RV battery and if you have electric trailer stabilizer jacks or an electric tongue jack that’s going to be a draw from the battery as well.
One way you can save power when using the slide-out or electric jacks is to leave the RV engine on or keep the truck plugged in. The running motor of the vehicle will power the slides and not rob power from the RV batteries. Using this same concept you can also charge your RV batteries in an emergency using your vehicle by plugging it in while the engine is running.
If your RV has an electric awning this will also be run by the 12V RV battery.
12 Volt Television
Some RV’s will have a 12V plug near the television so you have the option to run a 12V TV if you want. This is more common in class A or C RVs and 5th-wheels than it is in travel trailers. If your RV does have a 12V television you can expect it to use around 24 watts an hour if it’s a 19 inch TV. More power will be used the larger the TV screen is.
See Also: Best 12 Volt TV For RV/Campers/Skoolies
What Won’t RV Batteries Run?
When heading out to go dry camping or boondocking expect your RV batteries to only run the appliances listed above. You won’t be able to use your AC, microwave, electric water heater, electric fridge option, the wall outlets, or the TV in most cases. If your RV has an electric fireplace this is usually is run on 120V AC power because they are normally plugged in using a wall outlet.
As I said in the beginning of this article, you can use generators or solar generators to power your RV which will charge the batteries and let you use the wall outlets. Many people go with the generator options which works well for weekend camping but if you are planning on full-timing a solar power set-up that uses a solar generator and solar panels is going to be the better option.
Have any questions about 12V RV appliances and what your RV can run using the batteries? Leave a comment below.