Tuesday, September 26, 2023


Know Your RV: Use your water heater on gas or electric—or both?

Nearly all RV water heaters operate on LP gas; there are rare exceptions. But some RVs offer an option on their water heater: an electric heating element. How do you know if you have the optional electric element? If you do, how can you get the most advantage from either fuel option?

DSI versus “standing pilot”

Probably the most common ignition system for RV water heaters is called DSI, for “direct spark ignition.” It’s pretty convenient: Push a button inside your RV and your water heater lights up. We remember our early rigs, ones equipped not with DSI but with a “standing pilot.” When you wanted to use the water heater, somebody would get to go outside, open a cover, manually light a small pilot flame, make sure it stayed lit, turn some controls, and head back inside. The water heater was “on” all the time, burning up propane, until manually turned off—outside again.

water heater
R&T De Maris photo

A DSI switch is usually combined on a control panel that also controls the water pump, and may show holding tank levels. Most often found in the galley area, look your control panel over. In the photo above, you’ll see a control panel that includes the switch for “LP GAS”. To the right of the gas switch you’ll see one labeled “ELECTRIC”. This owner has a DSI gas water heater with the optional electric element. In the market? Here’s one on Amazon.

Make sure there’s water in that heater!

water heater
Base photo courtesy amazon.com

Switching on the gas side of the water heater is easy. Of course, make sure you have water in the heater. Many RVs are equipped with a “winterization” system that cuts the water heater out of the water supply. If your winterization bypass system is set to “winterize” and the water heater is empty, turning it on could lead to serious damage. The bypass system may still allow water to flow out of the hot water taps, but not allow water into the water heater.

If you don’t understand your bypass system, the only way to verify that your water heater has water in it (and is safe to “fire up”) is to do this: Go outside, open the water heater access door, and pull the handle on the pressure valve to ensure water flows out. Stand to the side so as not to get splashed. Let the valve handle loose when you see water flow out—it’ll snap back closed.

Turning it on

Now that you’re certain your water heater is full of water, you can turn the gas part of the heater on. Flip the control switch, and you’ll likely hear a “woosh” when the gas burner on the heater lights up. If there is a problem, the water heater will attempt to relight a set number of times. If it can’t light, for example if you’re out of propane gas, then an indicator light will turn on. You’ll see this indicator in the photo to the right of the LP gas switch. It’s labeled “DSI FLT”—indicating a fault in the direct spark ignition system.

Turning on the electric side is also easy. Generally you’ll find the switch for the electric element on the same control panel as that for the DSI. In some cases, an after-market electric element might have been added, and likely, no switch inside. If that’s the case, you’ll have to go outside, open the water heater access panel, and look for a switch to turn on the electric element, if there is one.

Gas or electric—Which is best?

So, what’s best to operate your water heater on—gas or electric? In terms of cost, gas is generally less expensive than electric, often several times less expensive. If electricity is included in an RV park rental bill, and not an added fee, many RVers will immediately choose electric operation.

There are a couple of other considerations, however. If your RV electrical service is 30-amp (three metal connectors on your electric cord where it plugs into the park pedestal), you’ll probably NOT be able to operate your water heater on electricity and use air conditioning, or the microwave oven, at the same time. Try and do it,  you’ll trip an electric breaker. If your rig has 50-amp service (four metal connectors on your electric cord), then you’ll likely be able to operate your water heater and other “big electric users” on electricity at the same time. Using an adapter to plug a 30-amp RV into a 50-amp connection WILL NOT solve this problem.

Keep in mind, it generally takes longer to heat up water using the electrical element than by using LP gas. However, if you’re in a pinch and need hot water in a hurry, you can safely turn on both the gas and the electric element on your water heater at the same time.

Hot water safety

Speaking of hot water, you’ve likely been spoiled by having an adjustable thermostat on your water heater at home. Most RV water heaters are equipped with a fixed, non-adjustable thermostat. The fairer writer of this article finds ours to be “too hot.” So use caution when you may come into “skin contact” with the hot water in your rig. Be safe, and enjoy your RV lifestyle!

Tune in next week for more “Know Your RV” tips. And if there’s something about your RV that you’d like to know, drop us a line. Use the form below, and insert “Know Your RV” on the subject line.

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Other stories by Russ and Tiña De Maris


Russ and Tiña De Maris
Russ and Tiña De Maris
Russ and Tiña went from childhood tent camping to RVing in the 1980s when the ground got too hard. They've been tutored in the ways of RVing (and RV repair) by a series of rigs, from truck campers, to a fifth-wheel, and several travel trailers. In addition to writing scores of articles on RVing topics, they've also taught college classes for folks new to RVing. They authored the book, RV Boondocking Basics.


  1. I recently had a pilot assembly replaced by an onsite repair service. He has been in the business for many years. He said that to keep more hot water available to turn on both the electric and gas at the same time and the recovery is much faster. He said the thermostat and tank don’t care how fast it heats The heater will cut off when it reaches temp. Has anyone heard of this or done it?

  2. If my math is right, discharging 100 Amp-Hrs of a 12 volt battery (1200 watt-hours of energy) is equivalent to about 6 oz of propane. Of course, there are conversion losses but this is intriguing. 

    It’s why I tend to change temperatures (furnace, fridge, heat water on the stove) with propane and keep my solar electricity for things that it does well: power computers, lights, stereo system, VPAP machine, etc. 

    Sponge baths with hot water from the stove work. My mother and two sisters did not have a shower in their residence until college. They heated water and used a pan. Somehow, they survived. I don’t use my RV water heater at all, and will remove it to reclaim the space.

    Air conditioning is a tough one, so I implement this simple rule: If it’s too hot for fans, shading, etc., then I am at the wrong latitude or altitude on the wrong date. Roll to cooler conditions.

  3. Our TT came with only gas, I installed one of the aftermarket electric heating elements into the WH not knowing how they performed but hoping it might at least act as a pre heater. As it turned out they work very well heating the water to between 105-115 degrees. It’s not as efficient as the gas system but it will heat fast enough that if 2 people take their showers a couple hours apart the gas system is not needed. If back to back showers are needed we turn on the gas for fast recovery times. As long as I’m paying for the electricity in the camping fee I may as well use the electricity.

  4. When plugged into 50 amps, life is easier. However, given a choice, I prefer to heat the Airstream with the quieter propane system than the @#$%& Dometic heat pump control system. Fill the Water tank, run the pump, flip the electric heat on, nice hot water in fifteen minutes.


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