Operating a Tankless Gas Water Heater Without Electricity


Tankless water heater

When the power goes out, hot water is one of the essential luxuries you risk losing. If you use a tankless gas water heater to provide your home with hot water, you may be wondering if you’ll have hot water in the event the power goes out. 

So, will a tankless gas water heater work without electricity? No, a tankless gas water heater still requires some electricity to operate. Tankless gas water heaters have an internal PC board, electronic ignition, and an electronic thermostat that requires electricity to operate. Without a power source, these components will not operate, preventing the tankless water heater from producing hot water.

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Tankless water heaters have a built-in PC board and digital remote that need electricity to operate the water heater. These components sense the flow of water and turn on the burner to generate hot water on demand.

Tankless water heaters also have a direct electric ignition that uses 120v power that lights the burners as hot water is needed. If the power is out, the ignition system will not operate.

While your gas-powered tankless water heater does need electricity to work, that electricity doesn’t have to come from your power outlet. If you experience a power outage, the best option is a portable generator that can power the tankless water heater and other household appliances and mechanicals such as the heating and cooling system, refrigerator, stove, lights, etc.

If a backup generator is not a viable option, a battery backup system can be installed to provide temporary power to the tankless water heater.

Concerned about installing a water heater outside? We address this concern in Can Water Heaters Be Installed Outside: What You Should Know.

Why gas-powered tankless water heaters need electricity

All tankless water heaters need electricity to function properly ‒ even gas-powered models. Electric heaters obviously need electricity to heat the water, but both need electricity to power their electronic control system, ignition system, and remote thermostats. 

The thermostat communicates to the control panel to operate the burners and ignition. When the power outage occurs, the heater will shut down and stop heating water.

Fortunately, there’s an easy and affordable way to keep your water heater operational when the power goes out. 

How to keep your tankless water heater running during a power outage

The best way to prevent hot water loss during power outages is by installing a battery backup system. These relatively inexpensive devices will connect to your tankless water heater and provide emergency electric power whenever your main source of electricity goes down. 

They don’t pack the same punch as a generator, but that’s the point ‒ it’s a cost-effective way to provide electricity to gas-powered devices that need it to function. A gas-powered tankless water heater is a perfect example of a device in need of a battery backup system. Without it, you lose the ability to do many things essential to living a civilized life. 

For information on protecting a water heater from freezing, see our article Maintaining Tankless Water Heaters in Freezing Temperatures

HUGO Battery Backup for Tankless Water Heaters

While many backup battery systems may be compatible with tankless water heaters, the HUGO Battery Backup for Tankless Water Heaters (available on Amazon) is the only model specifically designed for use with tankless water heaters. Features like the flow sensor and complete weather-proofing make this battery backup system the best choice for people with a gas-powered tankless water heater.

Water heater specificity aside, the HUGO is honestly a solid overall battery backup system. It has a standard power rating of 350W/500VA, making it compatible with almost all gas appliances. The pure sine wave output also ensures a longer device lifespan and more efficient power usage ‒ which translates to a lower energy bill. 

It’s also solar capable, which is a pretty big deal, in my opinion. Many backup battery systems need to charge up using the home’s main power source ‒ which can be a problem when the main power source is out for an extended period of time.

Because the HUGO is solar capable, you can connect it to a solar panel and charge it when you don’t have power. This is especially useful during long outages, as you can recharge your backup battery if it depletes its energy stores. 

To help you understand why the HUGO battery backup system works so well with tankless water heaters, I’ve listed a few defining features and explained how they could benefit your tankless unit. 

Flow sensor 

One of the most helpful features on the HUGO Battery Backup for Tankless Water Heaters is the built-in flow sensor. Although the HUGO has a decent battery that can handle up to 13 hours of continuous use, conserving that energy should still be a top priority ‒ especially when dealing with outages that last for more than a day. 

The flow sensor on the HUGO will help immensely with conserving energy. It will only activate and transfer energy to your water heater if it detects water flow. If no flow is present, the HUGO will remain in standby mode and use almost no energy. 

This feature makes the HUGO especially useful in locations where extended outages are a somewhat common occurrence. While using another model without a flow sensor is certainly viable, having the extra energy savings from a flow sensor might be the difference between a hot and cold shower in the midst of a snowstorm or other outage-causing weather events. 

Automatic switch over

In addition to being effective, the HUGO Battery Backup for Tankless Water Heaters is also convenient and user-friendly. The device can detect when your primary power supply is out and will shift your water heater to battery power within 8 milliseconds if an outage occurs. It will also automatically switch your heater back to your main power supply once the power has been restored. 

While this feature might seem minor, it’s one less thing you have to worry about when the lights suddenly go out. 

Indoor/Outdoor installation

While installing your backup battery system indoors to protect from freeze damage is preferred, it isn’t possible in all circumstances. 

Fortunately, the HUGO is fully equipped and graded for outdoor use in all kinds of weather. 

  • The exterior metal housing is incredibly thick. Sleet, hail, and other heavy precipitation will not dent the casing or affect the interior in any way. 
  • The unit has antifreeze assist technology, which will protect your hot water source in frigid temperatures ‒ which is the exact time having hot water is most important. 
  • The HUGO also has an IP54 grade, certifying it for protection in all sorts of different weather scenarios. An IP54 grade also specifically mentions total liquid protection ‒ so there’s zero chance rain gets in and damages internal components. 

Temporary or permanent mounting options 

Depending on your life situation, you might not want to install your battery backup system with a permanent, hard-to-remove mount. 

Maybe you’re going to be moving in a few months. Maybe you’ll be remodeling and will need to relocate your water heater. Whatever the case may be, the HUGO gives you flexibility in this area, as it offers both portable and permanent mounting options. 

Additional features 

While the features specifically designed for water heaters are the HUGO highlight, it has some other useful features worth mentioning. 

  • It has a built-in fuse to protect from circuit board overloads. This also protects your downstream hot water devices from power surge damage. 
  • A non-spill battery makes it even safer to place this device inside your home. 
  • You don’t have to use the HUGO with a tankless water heater. It is perfectly compatible with most other gas appliances too. 

The downsides 

While it does a great job for the price, the HUGO is not a perfect backup battery system. It has a few flaws that you should know about before making a purchase decision. 

First of all, the manufacturers made it so the flow sensor must be operational for the device to work. If you want to use the HUGO as a backup for something that isn’t a tankless water heater, you’ll need to open it up and disconnect the flow meter plug. This is a relatively simple process, but it can cause unexpected problems if you don’t know to do this. 

Next, the device isn’t exactly quiet. While the noise when it’s operational isn’t overwhelming or anything, it can get bothersome if you prefer a quiet home. Fortunately, the advanced weatherproofing on this machine makes putting it outside a safe bet. 

Finally, the HUGO makes a repetitive beeping noise when the power initially goes out. This beeping is supposed to signal that the power is out and that the heater’s power supply is switching to the backup battery system. However, after the first few beeps, it gets pretty annoying, especially if your water heater is located near one of your living spaces. Fortunately, the noise only lasts about ten minutes or so before shutting off. 

Installing the HUGO Battery Backup System

Installing the HUGO Battery Backup is relatively easy to do but does require some minor plumbing work. If you are uncomfortable with plumbing work, you should call a licensed plumber to assist with installing your HUGO Battery Backup system.

Step 1: Remove the battery from inside the HUGO case

The HUGO weighs 43 pounds in total. The interior battery weighs approximately 30 pounds. To lessen the weight when initially hanging the HUGO battery backup system, remove the interior battery. To remove the battery:

  1. Remove the four screws holding the interior L shaped bracket in place.
  2. Using the quick disconnect, disconnect the wiring to the battery.
  3. Remove the battery from the cabinet.

Step 2: Install the mounting brackets

The HUGO has four mounting brackets that need to be installed on the back of the cabinet. When installing the mounting brackets, be sure the keyholes are at the bottom of the bracket. Secure the brackets to the cabinet with the provides screws and washers. This will allow you to set the wall screws and hang the HUGO easily. You must install all four brackets to ensure the stability of the unit.

Step 3: Hang the HUGO cabinet

To hang the cabinet, you’ll need to set one screw initially. Setting the screws will depend on the mounting surface. In the video above, the unit is installed on a wood surface with wood screws. If you are mounting the cabinet outside, you’ll need to use mounting hardware designed for the exterior wall material. Anchors will be needed for masonry installation.

Hang the HUGO cabinet on the initial screw. Level the unit and install the remaining 3 screws. Tighten to the wall surface. Apply sealant over the screws if needed.

Step 4: Reinstall the battery

Now that the cabinet is installed, it;’s time to reinstall the battery inside the cabinet. Install the L shaped bracket and four mounting screws. Do not connect the cables yet. We will do this later.

Step 5: Install the flow switch

This is where you may need a licensed plumber. This is a relatively easy task, but you shouldn’t do this if you aren’t sure about what to do or do not own the correct tools to do the job.

  1. Power down the tankless water heater.
  2. Cutt off the cold water supply to the tankless water heater.
  3. Drain off the water supply by opening the water supply at a nearby sink.
  4. You’ll need to install the flow switch on the cold water line coming into the water heater.
  5. Apply Teflon tape on the threaded ends of the flow switch and install connections to the flow switch that matches the plumbing supply piping. The video shows installing the fittings for Pex piping, which is common in most homes. Pex does require a special crimping tool. Do not try to crimp the fittings with any other tools to damage the fittings and leak.
  6. Install the flow switch with the flow direction arrow is pointing towards the water heater. This is very important as the switch will only work in this direction.
  7. Be sure the flat portion of the flow switch is facing down.

Step 6: Check for leaks

Turn on the water supply and check for active leaks on the plumbing connections. If no leaks are present, you can proceed to the next step. If leaks are present, turn off the water supply to repair the plumbing connections.

Step 7: Plug in the flow switch

Now it’s time to plug in the flow switch. To do so, locate the side panel on the cabinet. Remove the four screws securing the cover in place and take out the power cord. Locate the port for the flow switch and plug it in. This will only fit in one direction.

Step 8: Plug in the tankless water heater

Inside the side panel, you’ll see an outlet to plug the water heater up. Once the water heater has been plugged in, reinstall the side panel. The gasket on the side of the panel seals the compartment from dust and moisture.

Step 9: Connect the battery cables

Inside the main cabinet door, reconnect the battery quick connect cables. Plug the unit into the wall outlet and turn the toggle switch on.

Step 10: Turn the water heater on

The installation of your HUGO battery backup system is complete. Power your water heater up and verify it is working properly.

HUGO Battery Backup System Check

Before locking the HUGO cabinet door, do a check system check. You can do this by looking at the indicator lights inside the cabinet. If power is on, the first green indicator light will be on.

You can simulate a power failure by unplugging the HUGO system from the outlet. When this happens, the second green light will indicate the system is operating on battery power. Confirm the water heater is on and producing hot water.

Upon completing simulation testing, plug the HUGO system back into the outlet, close, and secure the cabinet door. Congratulations, you’ve successfully installed your HUGO Battery Backup system.

Another feature the Hugo backup battery offers is the ability to integrate solar panels to charge the battery. This will allow you the option to provide power to run your gas water heater for lengthy periods of time in the event of a power outage.

The backup battery can carry the water heater for about 7 days of normal operation. Having solar panels added to the Hugo battery backup can provide unlimited charging and runtime when the power is out.

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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