Top 10 Battery Backups for Tankless Water Heaters

Nobody wants to find out their tankless water heater is useless during a power outage. But here’s the thing most people don’t realize: even gas-powered tankless heaters need electricity to run their ignition systems and control boards.

So when the power goes out, your hot water goes with it. No exceptions.

That’s exactly why a battery backup matters. The right system kicks in automatically and keeps your tankless heater running for hours, sometimes even days, without utility power.

We’ve tested and reviewed 9 of the best backup options to help you find one that fits your setup and budget.

Quick Comparison Chart

1. HUGO Battery Backup — Best Overall

The HUGO backup system sits at the top of this list because it was designed in particular for tankless water heaters. It features a large battery that provides up to 13 hours of continuous hot water usage during a power outage.

Its weather-resistant casing allows you to install it both inside and outside the house without fear of rain or other weather conditions. The built-in flow sensor makes sure the system only engages when it detects water flow, which provides efficient energy management.

The problem with the flow sensor feature is that the HUGO can’t be used as a backup for any appliance other than the water heater unless you remove the flow sensor. The device has a temporary or permanent mounting option for flexible installation.

The automatic switch-over function easily transitions your water heater from electric power to the HUGO battery backup and vice versa. It also features a built-in fuse and flow sensor to prevent board burnout and protect your water heater from power surges.

The HUGO battery is also solar capable, meaning you can connect it to solar panels for energy collection and backup. The built-in splash-proof battery makes it safe to install indoors by simply plugging it into a power outlet.

The HUGO machine isn’t totally quiet, and when the power goes out you can hear some noise when it’s working.

2. Ego POWER+ Nexus — Best Portable

If portability is important to you, the Ego Power+ is the right choice. It comes equipped with two sturdy steel handles and its compact, lightweight structure makes it convenient for outdoor usage like parties or camping.

The weather-resistant construction means you can use it outdoors without worry. It’s also usable indoors and can be stored on or underneath furniture while providing continuous uninterrupted hot water during a blackout.

The two included batteries provide excellent endurance for a device of this size, and the manufacturer assures you can rely on the power of this technology to eliminate the noise, vibrations, and fumes of a gas powered generator. The LED display shows running time using its built-in temperature sensor.

The Ego Power+ machine is as quiet as possible so you can use it indoors without being too disturbed. It doesn’t have an automatic starting system and you need to enable it manually, although the ignition process is fast and easy.

The Bluetooth and Wi-Fi connectivity makes it compatible with almost all gas appliances.

The Ego Power+ may seem expensive based on its size, but it’s a very reliable battery backup system.

3. ROCKPALS 500W — Best for Mobility

The ROCKPALS Power Station is a strong competitor for mobile use. One standout feature is its LED display that gives the user real-time data on the device’s status and operation.

It activates within 8ms of a power outage and auto-resets when main power becomes available. The device can be recharged via solar panels or your vehicle’s charging port, which will protect your hot water source in frigid temperatures.

The modern design is lightweight and easy to carry thanks to its built-in handle. Although it was manufactured for outdoor use, it’s not designed to withstand rain and thunderstorms.

Since it was designed for trekking, the manufacturer included an LED lamp that can send distress signals and protect downstream appliances. It can also be used indoors, placed on a piece of furniture or under a table.

It offers multiple options to protect your devices against voltage spikes.

The built-in alarm indicator for easy troubleshooting only goes off when the battery is low. If you’re looking for a backup battery for mobile use and are willing to invest more than four hundred dollars, the ROCKPALS is available at a reasonable price.

4. APC Smart-UPS X 2200VA — Best UPS

This UPS from APC is well-known for equipment quality in the battery backup market. Its indoor design can be rack or tower-mounted and discreetly inserted into adapted wall furniture.

The device is smart and autonomous in its operation, both for switching from utility power to backup mode and for clean power management. LED notifications provide information on status and running conditions.

If you choose one of the most powerful battery configurations, it provides up to 90 minutes of runtime at 300 watts. If you care about your consumption, the APC provides you with real data on kilowatt-hours consumed.

There’s also a mode that allows you to reduce the energy allocated to non-essential equipment to give more protection to the most sensitive equipment. The intuitive interface provides clear information with the ability to configure the inverter locally using easy-to-use navigation keys.

The APC Smart-UPS also has an operating system for remote checking and the integrated alarm lets you know the different states of use of the battery. The device isn’t expensive to acquire and on the field of maintenance it’s highly efficient and reliable.

5. Sonnen Batterie Eco 4 — Best Solar

Sonnenbatterie Eco isn’t only an excellent alternative to Hugo’s battery backup but it’s a real innovation. It’s a battery designed in the form of a modern wall cabinet connected to an inverter which in turn absorbs energy from solar panels.

You then supply not only your water heater but also your other gas appliances with clean energy, which will protect your hot water source in frigid temperatures. The first strong point of this model is its design which is chic and modern and allows it to blend harmoniously with your home furniture to the point of being forgotten.

In conjunction with the Sonnenback-up box, the system makes you completely forget or even fail to notice possible power outages. The Sonnen Batterie Eco Backup system assures you long hours or even a full day’s autonomy depending on capacity.

The energy management is intelligent and very well-organized. The collected energy is continuously distributed to power your equipment.

Excess energy stored in the battery becomes useful if there’s a blackout so that the Sonnen battery continues to power the house for long hours.

Unlike the Hugo backup, it doesn’t only supply energy to your water heater but to all the electrical equipment in your home and thus becomes a competitor of gas powered generators. With mobility, the Sonnen Batterie Eco isn’t easily movable despite its very nice design.

A final point that’s important to highlight is that the cost of acquiring the system is very high.

6. Generac 7043 — Best Heavy Duty

The Generac 7043 is the largest but also one of the most expensive backup solutions for tankless water heaters that we offer. If something huge doesn’t annoy you and you can afford it, the GENERAC 7043 incorporates a large battery that not only gives great autonomy for using your water heater but also allows it to support all the large appliances in the house when there’s a power outage.

We do, however, note that the manufacturer sells batteries separately. The battery charger enables it to recharge when the power is on and the battery lasts up to about 40 hours.

It can also be installed both inside and outside the house but due to its dimensions, we recommend that you install it outside.

As all its components are in a box certified corrosion-resistant aluminum the Generac 7043 can withstand weather variations. Unlike the HUGO and due to its design, the Generac 7043 has only a permanent mounting option.

It’s a choice of equipment made only if you’re looking at a long-term installation, since to acquire Generac 7043 you’ll need a budget of more than two thousand dollars.

For those who are looking for a low-noise device, the Generac is also designed and certified to meet this criterion. The remote control function allows the user to control the device operation remotely by a mobile application.

The multilingual LCD display allows the user to check the operating status of the generator at any time.

7. Tripp Lite OMNIVS — Best Budget

The Tripp Lite OMNIVS is a recommended alternative to the HUGO at a much lower price point. Its tower design is suitable for indoor installation and includes a wall mounting option.

Five LEDs on the front panel display power status, battery power, voltage regulation, and low battery status. The manufacturer promises up to 50 minutes of autonomy at 120 watts.

While the runtime is shorter than most other options on this list, it gives you plenty of time to use hot water and turn off your heater during a blackout. For under $200, you get built-in noise suppression and remote control functionality through a mobile application.

8. CyberPower CP1500AVRLCD — Best Value

The CyberPower CP1500AVRLCD features a compact tower design that you can easily store in any room. Its LCD display gives you all the information you need about the device’s status at a quick glance.

The CyberPower is so reliable in surge protection that the manufacturer offers an extended warranty on connected equipment if a power surge damages them. The intelligent voltage regulation system protects your connected water heater from high voltage damage.

Built-in management software keeps the UPS running quietly, while the audible alarm signals battery mode, low battery, overload, and errors. As an Energy Star certified product, it helps save money and protects the environment for under $200.

9. Ascent Solar Generator — Best Endurance

The Ascent Solar Generator Y1200 is a stylish and practical machine designed to keep your water heater running during power outages. It’s lighter than the average generator of this kind and features two sturdy handles for easy carrying.

The device offers multiple output ports to charge different types of devices. It’s compatible with solar panel recharging, and it’s powerful enough to run refrigerators, televisions, and power tools.

Don’t let its compact size fool you. This small unit hides enough power to supply your tankless water heater for about 16 hours during a power outage.

The Ascent Solar Generator also runs very quietly compared to generators with similar features.

What Is the Downside of a Tankless Water Heater?

This list isn’t meant to expose an exhaustive list of the best backup batteries for your water heater, but a selection of the best based on certain practical criteria.

The endurance criterion has allowed us to select the appliances that will allow you to use your water heater for the longest possible time in case of a power outage. For portable hot water needs during camping or off-grid situations, check out our best camping hot water heaters. The criteria of size and mobility as you’re a very mobile person and have a portable water heater makes sense to choose a backup battery system that’s also easily movable.

We’ve also considered battery backup systems that protect your water heater from voltage spikes and overloads.