Are Tankless Water Heaters Gas or Electric?
Tankless water heaters come in both gas and electric versions. The right choice for your home depends on what utilities you already have, how much hot water your household uses, and where you plan to install the unit.
Want to replace your water heater but don't know where to start? Take the residential water heater selector quiz to find personalized options based on your needs.
Article Summary
Tankless water heaters run on gas or electricity. Gas versions burn natural gas or propane to heat water quickly and can handle multiple showers running at the same time, but they need venting pipes to push exhaust outside. Electric versions don't need venting and fit in tighter spaces, but most homes need electrical panel upgrades to power them.
How Tankless Water Heaters Work
Gas and electric tankless water heaters work by heating water only when you turn on a faucet or shower. Cold water flows into the unit, where either a gas burner or electric heating elements heat it instantly to your set temperature.
The units adjust their heat output based on your incoming water temperature. If your water comes in colder during winter, the unit automatically increases heating to deliver the same hot water temperature you set.
Gas Tankless Water Heaters: What You Need to Know
Gas tankless water heaters use natural gas or propane to quickly heat water as it flows through the unit. These models can supply two or more showers running together without anyone losing hot water pressure or temperature.
Natural Gas vs. Propane Options
Natural gas models connect directly to your home's gas line for a continuous fuel supply without deliveries or refills. Propane models function the same way but pull from a propane tank on your property, making them a good fit for rural areas without natural gas service. The choice comes down to which fuel source you already have available.
Installation Requirements
Gas tankless water heaters need venting to send combustion gases outside. Vent pipes can be run through your roof or out of an exterior wall. Your home's gas line also has to supply enough fuel to keep up with the heater's demand. We recommend that you hire a professional for installation. They'll confirm your venting is set up right, your gas line can handle the load, and everything follows local codes.
Performance and Operating Costs
Gas tankless water heaters can run multiple showers while someone is doing laundry or running the dishwasher. No one experiences temperature drops or pressure loss when the system is sized correctly for your household. Natural gas typically costs less than electricity for heating water, though gas tankless models require a higher upfront investment for equipment and installation. Total costs for gas tankless water heaters vary based on the model size you need and your home's existing gas lines and venting setup.
Water Heater Selector Quiz
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Electric Tankless Water Heaters: Clean and Simple
Electric tankless water heaters connect to your home's electrical system and use heating elements to warm water as it flows through. They don't need venting since there's no combustion, which opens up more options for where you can install them.
Electrical Requirements
Electric tankless water heaters pull a lot of power from your home's electrical system. Most homes need electrical panel upgrades and new dedicated circuits to handle the load.
Have an electrician check your current electrical service before buying one. Older homes often need their main panel upgraded to support an electric tankless water heater.
When Electric Models Make Sense
Electric tankless water heaters fit well in smaller homes with one bathroom or as add-ons for a single sink or shower far from your main water heater. They also work when you don't have gas service or can't vent a gas unit. These models heat less water per minute than gas versions. One person can shower comfortably, but running two showers will stretch the system too thin.
Where You Can Install Them
Electric tankless water heaters don't need venting or gas lines, so you have more options for placement. You can mount them in closets, under cabinets, or other tight spaces as long as the electrical service reaches there.
Water Heater Selector Quiz
Need Help From A Pro?
A. O. Smith water heaters are professionally installed by local independent contractors.
Comparing Your Options: Which Type Is Right for You?
Your home's existing utilities can determine which tankless water heater is best for you. Here's how to decide:
When Gas Makes Sense
Gas tankless water heaters work best when:
- You have natural gas or propane service
- Multiple showers need to run simultaneously
- Lower fuel costs matter long-term
- You have space and budget for venting installation
- You want hot water during power outages
What Electric Models Offer
Electric tankless water heaters work best when:
- You don't have gas service
- You need a compact unit for tight spaces
- Hot water at one fixture is sufficient
- You can upgrade your electrical panel
A. O. Smith: Trusted Tankless Water Heating Solutions
A. O. Smith has built water heaters for over 80 years. Our ADAPT® line includes gas and electric tankless models. Gas versions have X3® Scale Prevention Technology that stops mineral buildup inside the unit. You never need the yearly cleaning most tankless water heaters require.
Not sure which type fits your home? Our XPERT™ Residential Water Heater Selector walks you through 8 simple questions about your household's hot water needs and recommends the right A. O. Smith model. Then connect with a certified local installer who can confirm your home's setup and handle the installation.
Frequently Asked Questions
Gas tankless water heaters work best for large families because they can supply multiple showers simultaneously while someone runs the dishwasher or washing machine, without temperature drops or pressure loss. For homes with multiple bathrooms and several people needing hot water at the same time, gas tankless provides the continuous hot water needed during busy mornings. Electric tankless models work better as supplemental units for a guest bathroom or single fixture rather than whole-home solutions for large families.
Tankless water heaters come in both gas and electric versions. Gas models burn natural gas or propane and can supply multiple fixtures simultaneously—ideal for larger households with several bathrooms. They work during power outages but need venting for combustion gases. Electric models use heating elements and don't need venting, making them perfect for tight spaces or homes without gas service. When sized appropriately, electric models provide continuous hot water for smaller applications like a single bathroom, though whole-home electric systems are available for homes with adequate electrical service.
Gas tankless water heaters need an existing gas line with adequate fuel capacity and venting through your roof or exterior wall. Electric tankless models require strong electrical service—whole-home units need dedicated high-amperage circuits, so homes with older electrical panels often need upgrades. Other factors include your incoming water temperature and the number of fixtures you use simultaneously. A professional installer can evaluate your gas lines, electrical panel, and venting options to confirm which system fits your home and meets local building codes.
Installing a tankless water heater yourself is not recommended. Gas tankless water heaters need precise venting to prevent carbon monoxide buildup and gas line connections that meet building codes. Electric models require high-amperage dedicated circuits and proper electrical panel connections—incorrect wiring creates fire hazards. Both types need plumbing connections, permits, and code-compliant installation. Most tankless water heater warranties require professional installation. Hire a licensed installer to ensure your system operates safely and to protect your warranty.