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.
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!
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!
Other stories by Russ and Tiña De Maris
##RVT1064
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.
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.
Actually, my tankless water heater requires both electricity and propane.
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.
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?
From a Plumber- Today’s code standard is between 110 to 120 depending on who is using it. Always best to test the temp before using it- no matter who is using it. RV thermostats are NOT of high quality or design.
Only commenting because I’ve actually had the water heater(electric) and AC on at the same time and occasionally use the microwave while both running and have never tripped the breaker since 2018. What am I missing?
This article is from 2022. Recently Dave Solberg published a screen shot of an Excel spreadsheet calculator to determine which provides the lesser cost hot water, electric or gas, for RV hot water tanks. You can read that article here.
I hate to admit it but I vacillate between gas and electric when disconnected. Propane typically costs a bit more than gasoline per gallon but it doesn’t add wear to my generator. If I’m running the generator to recharge the lithiums, burning propane on top of the gasoline seems silly as well.
Here’s my million dollar question:
What is most economical; Leave the hot water heater on all the time when camping or turn it on only for usage and off immediately after?
I’ve read it takes more energy to repeatedly heat cold water than it does to keep hot water hot and I’ve read it’s the opposite if you only use the hot water a couple times a day. Anyone out there test the theories?
I have not done a test, however IMHO it would be pennies in difference. Since we are already “lucky” enough to be able to afford RV’ing, this cost is negligible. Out of habit and for no other reason I do shut off the water heater after a morning shower and we still have enough hot water to do dishes in the evening.
I don’t think that we have a water heater, per se, in our RV. What we have heats the water with a diesel-fired burner, or electric heating elements. I think its primary purpose is heating the RV but that is seasonal. It does heat water year-round though. It is called Oasis and is an alternate to Aqua Hot.