Choosing between a gas vs. electric tankless water heater is not just a question of which fuel is cheaper. Both systems heat water on demand, but they differ in hot water output, installation requirements, energy costs, and the electrical or gas infrastructure your home needs.
A gas tankless water heater is often a strong choice for households with high simultaneous hot water demand, especially when natural gas service is already available. An electric tankless water heater can be compact and does not require combustion venting, but a whole-home model may need substantial electrical capacity and may struggle to deliver a high flow rate when incoming water is very cold.
This guide compares gas and electric tankless water heaters so you can decide which option fits your home, budget, and hot water needs.
Quick verdict: Choose gas if you need high flow rates and already have suitable gas service and venting. Consider electric if your hot water demand is modest, the electrical system can support the unit, or you need a compact point-of-use heater. Before buying either type, calculate your required flow rate in gallons per minute (GPM) and the temperature rise your heater must provide.
Gas vs. Electric Tankless Water Heater: Key Differences
| Feature | Gas tankless | Electric tankless |
|---|---|---|
| Heating source | Natural gas or propane | Electric resistance heating elements |
| Hot water output | Often better suited to high whole-home demand, depending on model and temperature rise | Ranges from small point-of-use units to whole-home models; output is limited by electrical capacity and temperature rise |
| Venting | Requires an approved combustion exhaust system; exact requirements depend on the model | No combustion exhaust vent is required |
| Utility requirements | A properly sized gas supply and an electrical connection for controls or fans on many models | Adequately sized electrical service, dedicated circuits, and wiring specified by the manufacturer |
| Installation complexity | Can be high if gas piping or venting needs upgrades | Can be high if the electrical panel, service, or wiring needs upgrades |
| Indoor installation | Requires approved venting and combustion provisions | Does not require combustion air or exhaust venting |
| Operating cost | Depends on gas prices, efficiency, usage, and maintenance | Depends on electricity prices, efficiency, usage, and required output |
| Best fit | Homes with high demand and suitable gas infrastructure | Lower-demand applications, point-of-use installations, or homes with sufficient electrical capacity |
Neither fuel is automatically cheaper or better in every home. The most important factors are the actual capacity required, installation cost, local utility rates, and how much hot water your household uses.
1. Hot Water Output: Which Type Can Handle More Showers?
For many households, hot water capacity is the most important difference between gas and electric tankless water heaters.
Gas tankless water heaters
Gas-fired units can provide substantial heating input, which often makes them suitable for homes that run several fixtures at once. A properly sized model may supply a shower while another person uses a sink or appliance, provided the required flow rate and temperature rise are within its performance limits.
However, gas units are not unlimited. Their output still depends on the model’s maximum heating capacity, gas supply, incoming water temperature, and the number of fixtures operating simultaneously.
Electric tankless water heaters
Electric tankless heaters can work very well for a single sink, bathroom, small application, or other limited hot water demand. Whole-home electric models are also available, but their output is constrained by the amount of electrical power the home can deliver.
In colder regions, incoming water can be much colder in winter. The heater must raise that water to the desired delivery temperature, and a greater temperature rise reduces the flow rate the unit can maintain. A model that performs adequately in a warm climate may not deliver the same flow in a colder one.
How much flow rate do you need?
Estimate which fixtures might operate at the same time, then add their expected flow rates. The following figures are illustrative planning estimates, not guaranteed values for every fixture.
| Fixture | Illustrative flow rate |
|---|---|
| Water-efficient shower | 1.5–2.0 GPM |
| Standard shower | 2.0–2.5 GPM |
| Bathroom faucet | 0.5–1.5 GPM |
| Kitchen faucet | 1.0–2.2 GPM |
| Dishwasher | Varies by appliance and fill cycle |
For example, a shower using 2.0 GPM and a kitchen faucet using 1.5 GPM would require approximately 3.5 GPM if they operate simultaneously. The selected heater must be able to provide that flow at the required temperature rise.
Use our detailed guide to what size tankless water heater you need to estimate GPM and temperature rise before comparing models.
2. Installation Requirements: Gas Line vs. Electrical Panel
The existing infrastructure in your home can determine which option is more affordable. A low-priced unit can become an expensive project if your house needs a major utility upgrade.
Gas tankless installation requirements
A gas tankless water heater generally requires:
- A natural gas or propane supply with enough capacity for the heater’s rated input.
- Gas piping sized according to the appliance, pipe length, other gas appliances, and applicable code.
- An approved combustion exhaust and venting arrangement for the specific model.
- Combustion air provisions where required by the appliance design and installation instructions.
- An electrical connection if required for ignition, controls, fans, or other components.
- Condensate drainage for condensing models.
- Required clearances, permits, and code-compliant installation.
Some high-efficiency condensing gas models use a secondary heat exchanger and require an approved vent system and condensate drain. ENERGY STAR explains these design differences in its guide to how gas tankless water heaters work.
If your home already has gas service, do not assume the existing pipe is large enough. A tankless unit can have a high instantaneous gas demand, especially when other gas appliances are running. A qualified installer must verify the supply and pressure.
Electric tankless installation requirements
An electric tankless water heater does not burn fuel, so it does not need a combustion exhaust vent or combustion air supply. Its main installation challenge is delivering enough electricity safely.
A whole-home model may require multiple dedicated circuits, appropriately sized conductors and breakers, and enough available capacity in the electrical service. Depending on the model and the home’s existing system, an electrical panel or service upgrade may be necessary.
Before buying, have a qualified electrician verify:
- The unit’s voltage, current, and circuit requirements.
- The number of dedicated circuits and the specified breaker sizes.
- The capacity of the existing panel and electrical service.
- Whether other major electrical loads can operate safely at the same time.
- Compliance with local electrical code and permit requirements.
Do not select a whole-home electric tankless unit based on its physical size alone. A compact heater can still require a major electrical upgrade.
For a more detailed installation checklist, read tankless water heater installation requirements.
3. Energy Efficiency: Is Gas or Electric More Efficient?
Efficiency ratings need context. Electric resistance tankless heaters convert nearly all the electricity they consume at the unit into heat, but that does not automatically mean they have the lowest operating cost. Electricity and natural gas have different prices, and the upstream energy used to generate electricity is not reflected in the same way as the heater’s on-site efficiency.
Gas tankless models lose some energy through combustion and exhaust. High-efficiency condensing units recover additional heat from combustion gases, improving their efficiency compared with conventional non-condensing gas tankless models.
ENERGY STAR states that its certified gas tankless models use a secondary heat exchanger and use about 9% less energy than conventional gas tankless water heaters. That is a comparison within the gas tankless category, not proof that gas is cheaper than electric in every home. See the official ENERGY STAR explanation.
When comparing individual products, review their published efficiency information, including Uniform Energy Factor (UEF) where applicable, and compare models using consistent test conditions. Do not rely on an efficiency percentage alone to predict your monthly bill.
4. Operating Costs: Which One Is Cheaper to Run?
The cheaper fuel depends on your local utility rates, hot water usage, and the efficiency of the exact models being compared. A gas heater can be cheaper to run where natural gas is relatively inexpensive. An electric model may be competitive where electricity rates are low or gas service is unavailable.
To estimate operating costs, consider:
- Your monthly hot water consumption.
- The temperature of incoming water and the temperature rise required.
- The unit’s energy consumption and efficiency rating.
- Your actual electricity rate in dollars per kWh or gas rate in dollars per therm.
- Fixed utility charges, where relevant.
- Maintenance costs and any efficiency changes over time.
A useful comparison should include both the initial installation and ongoing energy use. If one option requires a new gas line or extensive venting, while the other requires an electrical service upgrade, the installation difference can outweigh several years of projected energy savings.
For a broader view of water heating expenses, read how much it costs to run a water heater per month and whether a tankless water heater is worth it.
5. Upfront Cost and Installation Expenses
The purchase price is only one part of the project. Installation cost depends heavily on the home’s existing gas piping, venting, electrical service, plumbing layout, location of the heater, and local labor rates.
| Potential expense | Gas tankless | Electric tankless |
|---|---|---|
| Equipment | Varies by capacity, efficiency, and brand | Varies by capacity, electrical requirements, and brand |
| Utility upgrade | Possible gas piping or gas service upgrade | Possible panel, service, wiring, or circuit upgrade |
| Venting | Approved venting and termination may add cost | No combustion venting required |
| Condensate drainage | May be required for condensing models | Typically not needed for the heating process itself |
| Permits and labor | Depend on local code and installation scope | Depend on local code and installation scope |
There is no reliable universal installation price for either technology. Ask contractors to itemize equipment, labor, permits, venting or electrical work, gas piping, condensate drainage, and any required upgrades. Compare written quotes for systems that meet the same hot water demand.
6. Maintenance, Reliability, and Lifespan
Both gas and electric tankless water heaters can provide years of service when correctly installed and maintained. Their maintenance needs differ because gas units have combustion-related components that electric units do not.
Gas tankless maintenance
- Inspect the venting system and air intake according to the manufacturer’s instructions.
- Check for signs of gas leaks or combustion-related problems and arrange professional service if needed.
- Flush and descale the heat exchanger as recommended, particularly in hard-water areas.
- Inspect condensate drainage on models that produce condensate.
Electric tankless maintenance
- Follow the manufacturer’s instructions for descaling and flushing.
- Inspect plumbing connections for leaks.
- Have electrical connections checked by a qualified professional if there are signs of overheating, nuisance breaker trips, or other electrical problems.
- Address hard-water scale, which can reduce performance and damage components.
Water hardness, usage, installation quality, and maintenance all influence lifespan. Neither gas nor electric technology guarantees a particular service life. For more detail, see our guide to how long water heaters last.
7. Environmental Considerations
A gas tankless water heater burns natural gas or propane at the home, producing combustion emissions that must be vented safely. An electric tankless heater has no on-site combustion emissions, although the environmental impact of its electricity depends on how the power is generated.
If reducing household emissions is a priority, compare the local electricity mix, the efficiency of the proposed equipment, and your hot water consumption. You may also want to consider a heat pump water heater, which moves heat rather than generating all of it through electric resistance.
Explore our related guide to heat pump water heater vs. tankless to compare these technologies, and review the best heat pump water heaters of 2026 if you are considering an alternative.
8. Pros and Cons of Gas vs. Electric Tankless Water Heaters
| Option | Advantages | Disadvantages |
|---|---|---|
| Gas tankless | Often suitable for higher hot water demand; can deliver strong output; may have lower operating costs where gas is inexpensive | Requires gas service, approved venting, and combustion safety provisions; gas piping or vent upgrades can be expensive |
| Electric tankless | No combustion vent; compact; can suit point-of-use applications; no on-site fuel combustion | Whole-home models may require substantial electrical capacity; output can be limited at high temperature rise; electrical upgrades may be costly |
9. Which Is Better for Different Homes?
Choose gas tankless if:
- Your household has several bathrooms or frequent simultaneous hot water demand.
- You already have suitable natural gas or propane service.
- Your gas piping can support the required input, or an upgrade is cost-effective.
- You have a practical, code-compliant route for the required venting.
- Local gas prices make the projected operating costs attractive.
Choose electric tankless if:
- You need hot water at a single sink, bathroom, or other point of use.
- Your household’s required flow rate and temperature rise are within the model’s capacity.
- Your electrical service can support the heater without an uneconomical upgrade.
- You want to avoid combustion venting and on-site fuel combustion.
- Local electricity rates and installation costs make the overall project competitive.
Consider a different type of water heater if:
- You want high hot water capacity without relying on a large electrical service.
- Your home would require expensive gas and electrical upgrades for either tankless option.
- You prefer stored hot water to cover short periods of high demand.
- You want to compare the operating savings of a heat pump water heater.
A traditional tank water heater or a heat pump water heater may be a better fit depending on your household, utility prices, and installation conditions. Start with our complete water heater buying guide for a broader comparison.
Frequently Asked Questions
Is a gas tankless water heater better than an electric one?
Gas is often better for high whole-home hot water demand when gas service and venting are available. Electric can be a good choice for lower-demand applications or homes with sufficient electrical capacity. Neither is universally better.
Are electric tankless water heaters cheaper to run?
Not necessarily. Operating cost depends on local electricity and gas prices, hot water consumption, temperature rise, and equipment efficiency. Compare the expected energy use of specific models using your actual utility rates.
Does an electric tankless water heater need a special breaker?
Whole-home electric tankless models typically require dedicated circuits and breakers sized to the manufacturer’s specifications. The exact requirements depend on the model. A qualified electrician should verify the panel and service capacity before installation.
Does a gas tankless water heater need electricity?
Many gas tankless models need electricity for ignition, controls, and fans. Requirements vary by design, so check the manufacturer’s specifications. A gas heater should not be assumed to operate during a power outage.
Which tankless water heater is better in cold climates?
Both types must raise colder incoming water to the required delivery temperature. The best choice depends on the required GPM, the model’s output at that temperature rise, and the home’s utility infrastructure. Always check performance specifications for the expected winter inlet temperature.
Can an electric tankless water heater run two showers at once?
Some models may support multiple fixtures under suitable conditions, but many whole-home electric units have limited output at higher temperature rises. Add the expected fixture flow rates and compare the total with the model’s published performance at your incoming water temperature.
Do gas tankless water heaters need venting?
Yes. Gas-fired units need an approved system to exhaust combustion products. Vent materials, route, clearances, and termination requirements depend on the model and local code. Condensing units may also need condensate drainage.
Is a tankless water heater more efficient than a tank water heater?
Tankless units avoid the standby heat losses associated with storing hot water, but real-world savings depend on fuel type, usage patterns, efficiency, and installation. Electric tankless units may offer limited savings over conventional electric tanks in some homes, while gas tankless savings depend on the comparison unit and local fuel costs.
Final Verdict: Gas vs. Electric Tankless Water Heater
For many homes with high hot water demand, a properly sized gas tankless water heater is the stronger option when the property already has adequate gas service and a practical venting route. It can provide high output without requiring the same level of electrical capacity as a whole-home electric tankless unit.
An electric tankless water heater can be an excellent fit for point-of-use applications and selected homes where the electrical service can support the required output. Its lack of combustion venting simplifies some installations, but it does not eliminate the need for careful capacity planning.
Before you decide, calculate your peak GPM and temperature rise, verify the home’s gas or electrical capacity, and obtain itemized installation quotes. Then compare the total installed cost and estimated annual energy expense—not just the price on the box.
Sources and Further Reading
- ENERGY STAR — How Whole-Home Gas Tankless Water Heaters Work
- ENERGY STAR — Whole-Home Tankless Gas Water Heaters
- U.S. Department of Energy — Consumer Water Heaters
- U.S. Department of Energy — Measure Guideline: Transitioning to a Tankless Water Heater
Disclaimer: This article is for general informational purposes only and is not a substitute for professional advice. Gas piping, combustion venting, electrical service upgrades, and water heater installation must comply with manufacturer instructions and applicable local codes. Consult qualified professionals before selecting or installing equipment.