At a Glance
| Item | Details |
|---|---|
| Best For | Homeowners evaluating backup power for tankless water heaters |
| Estimated Reading Time | 9–11 minutes |
| Last Updated | July 2026 |
| Who Should Read This | Homeowners, RV owners, emergency preparedness planners |
| What You’ll Learn | Typical power requirements, gas vs. electric models, backup power options, and sizing considerations |
Introduction
If you’re wondering how much power a tankless water heater uses, you’re not alone. Understanding how much power does a tankless water heater use is important when planning backup power during an outage.
Although both are called “tankless water heaters,” their electrical requirements are dramatically different. Understanding those differences is essential when choosing a portable power station, backup battery, or generator.
This guide explains the typical electrical demands of each type, what happens during a power outage, and how to determine whether a portable power station is a practical backup solution.
For additional guidance on improving your home’s energy efficiency and reducing energy costs, visit the U.S. Department of Energy’s Water Heating page.
Printable Checklist
Before purchasing backup power, verify:
- Identify whether your unit is gas or electric.
- Locate the manufacturer’s electrical specifications.
- Record the required voltage.
- Record the maximum wattage or amperage.
- Determine whether whole-home backup is required.
- Compare the requirements with your planned backup power source.
How Much Power Does a Tankless Water Heater Use?
The answer depends on the type of unit installed.
How Much Power Does a Gas Tankless Water Heater Use?
Gas tankless water heaters use natural gas or propane to heat water. Electricity powers only the electronic controls, ignition system, display, and combustion fan.
Typical electrical consumption:
- Running power: 50–200 watts
- Startup surge: Usually minimal
- Backup with a portable power station: Often practical
Because the electrical load is relatively low, many gas tankless units can continue operating during an outage if connected to an appropriately sized portable power station.
How Much Power Does an Electric Tankless Water Heater Use?
Electric models are entirely different.
Instead of burning gas, they use high-powered electric heating elements that activate whenever hot water is needed.
Typical electrical demand:
- 8,000–36,000 watts (depending on model)
- Multiple dedicated 240-volt circuits
- Very high current draw
Most consumer portable power stations are not designed to power whole-home electric tankless water heaters because of these substantial electrical requirements.
Why the Difference Matters
Many homeowners assume every tankless water heater has similar power needs. In reality, the difference between gas and electric models can be enormous.
For example:
- A gas unit may require less electricity than a desktop computer.
- A whole-house electric unit may require more power than an entire portable power station can deliver.
Knowing which type you own prevents purchasing a backup system that cannot support your equipment.
Factors That Affect Power Consumption
Several variables influence actual electrical usage:
Heater Type
Gas-fired units consume very little electricity, while electric models rely entirely on electrical heating elements.
Flow Rate
Larger units capable of supplying multiple showers simultaneously generally require more power.
Incoming Water Temperature
Colder incoming water requires more heating energy, increasing electrical demand for electric models.
Household Hot Water Demand
Higher usage means the heating elements operate more frequently, increasing overall energy consumption.
Can a Portable Power Station Run a Tankless Water Heater?
Whether a portable power station can operate a tankless water heater depends entirely on the type of unit installed.
Gas Tankless Water Heaters
In many cases, yes.
Most gas-fired units require relatively little electricity to operate the control board, electronic ignition, exhaust fan, and display. A properly sized portable power station can often provide enough AC power to keep the unit functioning during a power outage, provided natural gas or propane service remains available.
Always verify the manufacturer’s electrical requirements before connecting any backup power source.
Electric Tankless Water Heaters
Generally, no.
Whole-house electric tankless water heaters commonly require between 8,000 and 36,000 watts, operate on 240-volt circuits, and draw far more power than consumer portable power stations are designed to deliver.
If maintaining hot water during an extended outage is essential, homeowners typically consider:
- Whole-home standby generators
- Large home battery backup systems
- Hybrid backup solutions designed for critical household loads
Estimating Operating Costs
Although gas tankless water heaters use very little electricity, electric tankless models can become one of the largest electrical loads in a home.
Factors affecting operating cost include:
- Local electricity rates
- Household size
- Hot water usage
- Incoming water temperature
- Heater efficiency
Because tankless units heat water only when needed, many homeowners experience lower annual energy costs compared to traditional storage tank water heaters.
Choosing the Right Backup Power Solution
Before investing in backup power, answer these questions:
Do You Have a Gas or Electric Unit?
This single question determines whether a portable power station is even a realistic option.
What Does the Manufacturer Specify?
Review the owner’s manual or product label for:
- Voltage
- Running wattage
- Maximum amperage
- Circuit requirements
What Other Appliances Need Backup Power?
Many homeowners prioritize:
- Refrigerator
- Freezer
- Internet equipment
- Medical devices
- Lighting
- Phone charging
If these essential loads are combined with a gas tankless water heater, selecting the appropriate backup power system becomes much easier.
Expert Tips
- Photograph the specification label on your water heater before an emergency.
- Test your backup power plan before storm season.
- Keep extension cords organized and labeled if your backup setup requires them.
- Review your homeowner’s manual annually.
- If you’re unsure about electrical requirements, consult a qualified electrician.
Common Mistakes to Avoid
Avoid these common errors:
- Assuming all tankless water heaters have the same power requirements.
- Purchasing a portable power station without checking surge and continuous output ratings.
- Ignoring voltage requirements.
- Forgetting that gas models still require electricity for electronic controls.
- Attempting to connect high-power electric tankless units to equipment that cannot safely support them.
Frequently Asked Questions
Does a gas tankless water heater need electricity?
Yes. Although the water is heated by natural gas or propane, electricity powers the electronic controls, ignition system, and exhaust fan.
Can I run an electric tankless water heater from a portable power station?
In most cases, no. Whole-home electric tankless units require substantially more power than portable power stations can safely provide.
How do I know which type I have?
Check the manufacturer’s label or owner’s manual. Gas models are connected to a gas supply, while electric models typically have multiple dedicated 240-volt electrical circuits.
Is a generator better for an electric tankless water heater?
For most whole-house electric models, a properly sized standby or portable generator is generally a more practical backup solution than a consumer portable power station.
Key Takeaways
- Gas and electric tankless water heaters have dramatically different electrical requirements.
- Most gas tankless units require only modest electrical power for controls and ignition.
- Electric tankless water heaters often require thousands of watts and multiple 240-volt circuits.
- Always verify your specific model before purchasing backup power equipment.
- Understanding your water heater’s electrical requirements helps you select the safest and most effective backup solution.
Conclusion
When homeowners ask “How much power does a tankless water heater use?”, the most important distinction is whether the unit is gas-fired or fully electric. Gas tankless water heaters generally use very little electricity and may be compatible with appropriately sized portable power stations, while whole-house electric models typically require far more power than portable battery systems can provide. By identifying your specific unit, reviewing the manufacturer’s specifications, and planning your backup strategy in advance, you’ll be better prepared to maintain essential hot water during future power outages.