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Do Tankless Water Heaters Work When the Power Goes Out?


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The short answer? No. Your tankless water heater will not work when the power goes out in your home. In fact, this is one of the downsides of installing a tankless system, but that doesn't mean you don't have options. This article will give you several ways to deliver hot water during a power outage.

One of the main benefits of the traditional tank-style water heater is it's ability to store hot water. When there's a power outage, you would still have a large insulated tank with a reserve of hot water at the ready. But tankless systems are completely different.

Unfortunately, electric tankless water heater models need and draw a lot of energy when they're being run. Some homes even need to have their household electrical system upgraded when switching to a tankless system. Whole-house tankless models often come with four 7,000-watt heating elements, pulling 28,000 watts when in use.

Even with gas-fueled tankless water heaters, electricity is required to power many of the critical components such as the control panel, fans, flow sensors, thermostat, and pilot light. Without power, the water heater is unable to set temperatures, regulate water entry and exit, and even light the burners.

Battery with red top

Solutions for Tankless Water Heaters in Power Outages

Thankfully, there are a few solutions to your tankless water heater's main flaw of needing power.

If you experience power outages with enough frequency to believe it may hinder your water heating system should you go tankless, consider the following options.

HUGO Battery Backup for Tankless Hot Water Heater & Gas Appliances - Backup Battery Power Supply with Flow & Temperature Sensors - IP54 Weatherproof, Waterproof, Anti-Freeze - Emergency Charging Unit

Water Heater Backup Battery

Brands like HUGO sell battery backup packs intended for use on a tankless water heater when the power goes out. These units are compact and easy to install, they stay plugged in, and are able to provide long-term power to a water heating unit.

The HUGO back-up battery can supply up to 14 hours of continuous hot water, or up to 7 days of regular usage during power outages.

Make sure to check with your water heater technician and the manufacturer of your unit to see which third-party backup batteries are compatible with your model of tankless water heater.

It's preferable to purchase a backup battery only for gas-fueled units as they require the least amount of electricity to run. The pilot light and the control panel are the main draws of electricity.

For electrical tankless models, however, a  significant amount of electricity is needed to heat the elements. It may be better to think about generators for electrical units, rather than battery packs.

WEN DF475T Dual Fuel 120V/240V Portable Generator with Electric Start Transfer Switch Ready, 4750-Watt, CARB Compliant

Back-up Generator

A back-up generator can come in many forms. The most obvious would be a generator that could power your entire home. These units deliver a lot of power, but they're also cumbersome and require a lot of fuel.

If you live in a remote location, or in an area often subject to power outages, a whole-house back-up generator may be an investment worth considering, especially if you live in the northern hemisphere.

However, if the generator is only for the infrequent moments you lose electricity, you may want to look into a point-of-use generator that can be used to power a single appliance.

For instance, you could save fuel in a power outage by only turning the generator on when you need hot water and then turning it off when it is no longer required.

This type of generator could also be plugged into your dishwasher or laundry machine if needed. 

When it comes to choosing a generator, there are a lot of models to choose between such as the WEN DF475T Dual Fuel. But before purchasing one, it's always a good idea to check that it will generate enough power to fuel your tankless water heater.

Camplux 5L Outdoor Portable Water Heater, 1.32 GPM Tankless Propane Gas Water Heater for RV, Camping, Barns, White

Portable Propane Tankless Water Heaters

Another alternative would be to have a small back-up tankless water heater that uses propane as its fuel source, such as this one from Camplux.

Many portable tankless models are designed to not need access to any power, and they're able to perform basic water heater functions without a central control panel.

A portable propane tankless water heater would be for short-term use only, but it is an effective solution to delivering hot water during a power outage.

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