Electric tankless water heaters heat water on demand instead of storing it in a tank

An electric tankless water heater for an RV heats water the moment you turn on a faucet, rather than keeping a full tank hot all the time. Cold water flows through a heating chamber where electric coils or elements rapidly warm it to your set temperature, then delivers it to your tap. The main advantage is space — tankless units are compact enough to fit under a cabinet or in a tight corner, whereas a traditional tank takes up significant room in an RV where every inch matters.

The trade-off is power demand. Electric tankless heaters draw a lot of current from your RV's electrical system, which means you need either a large battery bank, a generator, or shore power (a 30-amp or 50-amp connection at a campground) to run one reliably. Many RV owners use them only when plugged in at a campground, not while boondocking on battery alone.

Key Takeaways

  • Electric tankless heaters require significant power draw, typically 5,500 to 13,000 watts, so they work best when your RV is connected to shore power.
  • Tankless units take up far less space than traditional water tanks and heat water when ready without storing it.
  • Flow rate (measured in gallons per minute) determines how many fixtures you can use at once; most RV models handle 2 to 4 GPM.
  • Installation requires running dedicated electrical circuits and may need upgrades to your RV's electrical panel or breaker system.
  • Propane tankless heaters are an alternative if you want to reduce electrical load and can accept the added weight and complexity.

Power requirements and electrical setup

Electric tankless water heaters are power-hungry devices. A typical RV model draws between 5,500 and 13,000 watts depending on the temperature rise you want and the flow rate. To put that in perspective, a standard 30-amp RV service provides about 3,600 watts total for everything in your rig — lights, refrigerator, air conditioning, and water heater combined. Running a full-size electric tankless heater on 30-amp shore power alone means you cannot run much else simultaneously.

If your RV has 50-amp service, you have more headroom. A 50-amp connection provides roughly 12,000 watts, which is enough to run a tankless heater and other appliances at the same time. However, you still need to check your RV's main breaker and internal wiring to confirm they can handle the load. Many RVs require an electrician to install a dedicated circuit breaker for the tankless unit.

Boondocking (camping without shore power) on battery alone is not practical with an electric tankless heater. A typical RV lithium or lead-acid battery bank cannot sustain the draw for more than a few minutes. If you plan to camp off-grid frequently, a propane tankless heater or a traditional propane water tank is a better choice.

Flow rate and how many fixtures you can use

Flow rate is the amount of hot water the heater can produce at once, measured in gallons per minute (GPM). Most RV electric tankless heaters deliver 2 to 4 GPM. That sounds like enough until you try to shower while someone runs the kitchen sink — suddenly you have two fixtures drawing from the same heater, and the temperature drops or the flow weakens.

A 2 GPM unit is suitable for a single fixture at a time: a shower or a sink, but not both. A 3 to 4 GPM model gives you more flexibility, though even then, running a shower and a sink simultaneously may reduce water temperature slightly. If your RV has multiple bathrooms or you want to use hot water in two places at once, you need either a higher-flow unit or a second heater.

The flow rate also depends on how much temperature rise you need. If your incoming water is already warm (in summer or in warm climates), the heater can deliver more GPM at your desired temperature. In cold climates or winter, the same heater produces less hot water because it has to work harder to raise the temperature of cold incoming water.

Installation considerations and costs

Installing an electric tankless water heater in an RV is not a straightforward swap. You need to remove the old water tank (or leave it in place if space allows), run new water lines to the heater location, and run a dedicated electrical circuit from your main breaker panel to the unit. Most installations also require a new breaker sized for the heater's amperage draw.

The water lines must be insulated to prevent heat loss, especially if the heater is far from your fixtures. You may also need to install a mixing valve to prevent scalding if the heater produces water hotter than your fixtures can safely handle. Some RV owners hire a mobile RV technician to handle the installation; others do it themselves if they have electrical and plumbing experience.

Total installation cost varies widely depending on whether you do the work yourself or hire a technician, and whether your RV's electrical system needs upgrades. A DIY installation with a mid-range tankless heater might run $800 to $1,500 in parts. Professional installation can add $500 to $2,000 or more, depending on the complexity of your RV's layout and existing systems.

Comparing electric tankless to propane tankless

Propane tankless heaters are the other common option for RVs. They produce hot water on demand like electric models, but they draw power from your propane tank instead of your electrical system. A propane heater uses only a small amount of 12-volt DC power to ignite and control the flame, so it works well when boondocking on battery.

The trade-off is weight and complexity. Propane heaters are heavier than electric ones, and they require venting to the outside of your RV (similar to a furnace). They also need regular maintenance to keep the burner clean and the ignition system working. Propane heaters typically cost more upfront than electric models, but they offer better independence from shore power.

If you spend most of your time at campgrounds with shore power, an electric tankless heater is simpler and cheaper. If you boondock frequently or want to reduce your propane consumption, a propane tankless heater makes more sense despite the added complexity.

Temperature control and mixing valves

Electric tankless heaters heat water to whatever temperature you set, which can be very hot — sometimes 140°F or higher. To prevent scalding and to deliver comfortable shower water, most installations include a mixing valve that blends hot water with cold water to reach a safe temperature (usually around 110°F to 120°F for showers).

Without a mixing valve, you risk turning on the hot water tap and getting water hot enough to cause burns, especially if someone is showering and another fixture suddenly draws cold water, causing the heater to spike its output. A mixing valve is inexpensive (typically $30 to $100) and is considered a safety essential in most RV installations.

Some tankless heaters have built-in temperature controls that let you set a maximum output temperature, which reduces the need for a separate mixing valve. Check your heater's specifications to see what it offers.

Maintenance and lifespan

Electric tankless heaters have fewer moving parts than propane models, so they generally require less maintenance. The main concern is mineral buildup inside the heating chamber, especially if you travel in areas with hard water. Over time, calcium and magnesium deposits can reduce flow rate and heating efficiency.

To prevent buildup, you can flush the heater periodically with a descaling solution (a mixture of white vinegar and water works for mild cases). Most manufacturers recommend flushing once a year if you have hard water, or every few years if your water is soft. The process takes an hour or two and costs little beyond the descaling solution.

A well-maintained electric tankless heater typically lasts 10 to 15 years. Propane heaters may need burner cleaning or ignition repairs sooner, depending on use and water quality. Both types eventually fail and need replacement, but electric models are usually simpler and cheaper to repair if something goes wrong.

Frequently Asked Questions

Can I run an electric tankless water heater on my RV's battery alone?

No. Electric tankless heaters draw too much power for batteries to sustain. Even a large lithium battery bank would drain in minutes. You need shore power (30-amp or 50-amp campground connection) or a generator to run one reliably.

What size tankless heater do I need for my RV?

Look for a model with 3 to 4 GPM flow rate if you want to use multiple fixtures at once. If you only need hot water for a shower or sink, a 2 GPM unit is sufficient. Check the heater's power draw to make sure your RV's electrical service can handle it.

Do I need to replace my old water tank if I install a tankless heater?

Not necessarily. Some RV owners remove the old tank to save weight and space. Others leave it in place as a backup or for storage. Leaving it in place takes up room but gives you a safety net if the tankless heater fails.

Will a tankless heater work in cold weather?

Yes, but with reduced flow rate. Cold incoming water requires more heating power, so the heater produces less hot water per minute in winter than in summer. In freezing temperatures, you may need to insulate the water lines and heater to prevent freeze damage.

How much does an RV electric tankless water heater cost?

Heater units typically range from $400 to $1,200 depending on flow rate and features. Installation adds $500 to $2,000 if you hire a technician. DIY installation with parts might total $800 to $1,500.