Gas vs. Electric Water Heaters: How They Differ

The fuel a storage tank uses changes far more than the energy bill. It changes how fast the tank reheats after a long shower, what the heater does when the power goes out, what the installation actually requires behind the wall, and whether the unit has a flame and a vent to worry about at all. Those differences, not a single “which is cheaper” verdict, are what usually decide the choice. This guide compares the two fuel types on the axes you actually feel day to day, and it is honest about the one axis (operating cost) where no general answer holds.

Both types do the same job: they keep a tank of water hot and ready. According to the U.S. Department of Energy, conventional storage water heater fuel sources include natural gas, propane, fuel oil, and electricity. Natural gas is available in many areas of the country, while electricity is widely available. What follows assumes you have a real choice between a gas-fired and an electric tank. If only one fuel reaches your home, that constraint often settles the question before any of the trade-offs below come into play.

How Each One Heats Water: Burner and Flue vs Electric Elements

A gas tank heats from underneath with a flame; an electric tank heats from inside with elements.

In a gas-fired storage heater, a burner sits below the tank and fires up when the thermostat calls for heat. The flame heats the bottom of the tank, and the hot combustion gases rise up through a flue that runs through the center of the tank, giving up heat to the water on the way out. Those gases then leave the house through a vent. That flue path is also why gas and oil heaters carry an extra penalty the DOE calls venting-related energy losses: some heat goes up the vent rather than into the water.

An electric storage heater has no flame, no burner, and no flue. Instead it uses electric heating elements that sit directly in the water. Most residential electric tanks have two elements, an upper and a lower one, that switch on as the water around them cools. Because the heat is added straight into the water with nothing venting to the outside, an electric tank avoids the flue losses a gas unit has. Both fuel types still lose some heat through the tank walls even when no one is drawing water, which the DOE calls standby heat loss.

This single structural difference, a vented flame underneath versus elements submerged inside, is the root of almost every other difference in this guide.

Recovery Rate and First-Hour Delivery: Where Gas Usually Leads

Recovery rate is how quickly a tank can reheat a fresh batch of cold water after you have drawn down the hot. Gas tanks generally recover faster than comparable electric tanks of the same size.

The reason is how much heat each source can pour in. The DOE explains that a tank’s first hour rating, the gallons of hot water it can deliver in a busy hour starting full, depends on tank capacity, the source of heat, and the size of the burner or element. A gas burner can typically add heat to the water at a higher rate than standard electric elements can, so a gas tank refills its hot supply sooner. The DOE makes a related point for on-demand units: a 70 degree Fahrenheit temperature rise is possible at about 5 gallons per minute through a gas-fired demand water heater versus about 2 gallons per minute through an electric one. That gap reflects the same underlying truth for tanks, that gas can deliver more heat input per hour.

What this means in practice: if your household runs back-to-back showers or fills a large tub, a gas tank of a given size is more likely to keep up, and an electric tank of the same size may need a longer wait to fully recover. The fix on the electric side is usually to size up the tank or its first hour rating rather than expect faster reheating. To compare models on the metric that actually predicts running-out, the DOE recommends choosing by first hour rating rather than tank size alone. The detailed how-to of sizing for your household belongs in our guide on water heater sizing (063), so this post stays focused on the fuel comparison itself.

Operating Cost: Why It Depends on Your Local Energy Prices

There is no honest universal answer to “is gas or electric cheaper to run.” It depends on the price of gas and electricity where you live.

This is the axis where generic comparisons go wrong, so it is worth being blunt. The DOE is explicit that fuel type alone does not determine operating cost, and it tells homeowners to contact their utility for current fuel costs or rates. It even gives a counterintuitive example: an electric heat pump water heater might have lower energy costs than a gas-fired conventional storage water heater, even where local natural gas prices are lower than electricity rates, because efficiency, not just fuel price, drives the bill. The DOE also cautions that a higher energy factor does not always mean lower annual operating costs, especially when you compare different fuel sources.

So the practical move is to compare three things for your own address: the local price of natural gas, the local price of electricity, and the efficiency rating of the specific models you are weighing. A standard electric resistance tank and a heat pump water heater are both “electric” but have very different running costs, which is why fuel type alone cannot tell you the answer. If you want to dig into efficiency itself, see our guide on making a water heater more energy-efficient (066). Any dollar figure you see quoted as a flat “gas saves you $X a year” should be treated with suspicion unless it is built on your local rates.

Installation Needs: Gas Line and Venting vs Electrical Circuit

A gas tank needs a gas supply and a vent to the outdoors; an electric tank needs an adequate electrical circuit. Switching fuel types adds real cost because you have to build whatever the new heater requires.

An electric storage heater connects to a dedicated electrical circuit sized for its elements, typically a 240-volt circuit in a U.S. home. It has no combustion, so it needs no gas piping and no flue. That simplicity is part of why electric tanks can go in closets and interior spaces where venting a flame would be difficult.

A gas tank needs two things an electric tank does not: a gas line delivering fuel to the burner, and a vent that carries combustion gases safely outside. It also needs enough combustion air reaching the burner to burn cleanly. The DOE flags this directly when discussing fuel conversion, listing “adding a breaker or running a gas line to the water heater and venting it outside” among the extra cost considerations of switching fuels. In other words, the heater is only part of the bill if you change fuel types.

Sizing the vent, providing combustion air, and connecting gas piping are governed by code, and the requirements vary by jurisdiction. The International Fuel Gas Code and the fuel-gas provisions of the International Residential Code set the rules for venting and combustion air, and local jurisdictions adopt their own versions and amendments. This is licensed work. Gas line and venting installation is not a do-it-yourself task, and this guide gives no steps for it. Have a licensed plumber or qualified gas installer size and connect the gas supply and venting and confirm what your local code requires. The general picture of gas piping and why it is pro-only is covered in our guides on how residential gas lines work (172) and why you should never DIY gas line work (174).

What Happens in a Power Outage With Each Type

When the electricity goes out, the difference between the two fuels becomes very practical.

An electric storage tank stops making new hot water the moment the power fails, because its elements cannot run without electricity. You still have whatever hot water is already in the tank, but once that is drawn down, it stays cold until power returns. Heat pump water heaters are electric too, so they behave the same way.

Gas tanks split into two camps depending on how they light the burner. A gas heater with a standing pilot light, a small flame that stays lit continuously, does not depend on household electricity, so it can keep heating water through an outage. A gas heater with electronic ignition is different: it uses electricity to light and control the burner, so without power, or without its own battery backup or a generator, it will not fire either. So “gas works in an outage” is only reliably true for the older standing-pilot style. If outage performance matters to you, the ignition type of the specific gas model is the detail to check, not just the fuel.

Venting and Combustion Safety Considerations Unique to Gas

A gas water heater burns fuel inside your home, which creates safety responsibilities an electric tank simply does not have. This is the part of the gas-versus-electric decision that is about safety, not convenience.

Because a gas unit produces combustion gases, it must vent them fully to the outdoors and must draw enough combustion air to burn cleanly. When venting or combustion air is wrong, a gas appliance can spill exhaust, which can include carbon monoxide, back into the living space. That is why the venting and combustion-air rules above are code-required and pro-installed rather than optional. A working carbon monoxide alarm is a sensible companion to any fuel-burning appliance.

Gas also brings the possibility of a fuel leak, which electric tanks have no equivalent of. Utilities add a rotten-egg odorant to natural gas so a leak can be smelled. The U.S. Consumer Product Safety Commission is direct about what to do: if you smell or hear gas leaking, leave your home immediately and contact your local gas authorities from outside the home, and do not operate any electronics, such as lights or a phone, before leaving. Recognizing a leak and responding to it is covered in our guide on how to recognize a gas leak and what to do (173).

None of this makes a gas heater unsafe when it is installed and vented correctly by a professional. It does mean a gas tank carries a category of risk, combustion and venting, that an all-electric tank does not, and that is a fair thing to weigh alongside recovery speed and operating cost.

Frequently Asked Questions

Is a gas or electric water heater cheaper to run?
It depends entirely on local energy prices. The Department of Energy says fuel type alone does not determine operating cost and advises contacting your utility for current gas and electricity rates. Efficiency matters too: an electric heat pump water heater can have lower energy costs than a gas tank even where gas is the cheaper fuel. Compare your local gas price, your local electricity price, and the specific models’ efficiency before assuming either is cheaper.

Which heats water faster, gas or electric?
Gas tanks generally have a faster recovery rate, meaning they reheat a fresh batch of cold water sooner than a comparable electric tank, because a gas burner can deliver more heat per hour than standard electric elements. An electric tank of the same size may need a longer wait to fully recover, which is why first hour rating, not just tank size, is the number to compare.

Will my water heater work during a power outage?
An electric tank stops making new hot water during an outage, though you keep whatever is already heated in the tank. A gas tank with a standing pilot light can keep heating because it does not need household electricity. A gas tank with electronic ignition will not run during an outage unless it has battery backup or a generator, so check the ignition type if outage performance matters.

Does a gas water heater need a vent?
Yes. A gas unit produces combustion gases that must vent fully to the outdoors, and it needs adequate combustion air to burn safely. Venting and combustion air are governed by code that varies by jurisdiction, and the installation is licensed work, not a do-it-yourself job. An electric tank has no flame and no vent.

Can I switch my electric water heater to gas myself?
No. Converting fuel types means adding a gas line and venting (or, going the other way, a suitable electrical circuit), which the DOE lists as significant added costs. Gas line and venting work is licensed, code-governed work. Have a licensed plumber or gas professional handle the conversion and confirm local code requirements.

This article is general information, not professional advice. Gas, venting, and combustion-air work must meet local code and should be performed by a licensed professional; consult one for your specific situation.

Sources

• Storage Water Heaters, U.S. Department of Energy: https://www.energy.gov/energysaver/storage-water-heaters
• Selecting a New Water Heater, U.S. Department of Energy: https://www.energy.gov/energysaver/selecting-new-water-heater
• Estimating Costs and Efficiency of Storage, Demand, and Heat Pump Water Heaters, U.S. Department of Energy: https://www.energy.gov/energysaver/estimating-costs-and-efficiency-storage-demand-and-heat-pump-water-heaters
• Tankless or Demand-Type Water Heaters, U.S. Department of Energy: https://www.energy.gov/energysaver/tankless-or-demand-type-water-heaters
• Sizing a New Water Heater, U.S. Department of Energy: https://www.energy.gov/energysaver/sizing-new-water-heater
• Safety of Natural Gas Appliances, U.S. Consumer Product Safety Commission: https://www.cpsc.gov/content/Safety-of-Natural-Gas-Appliances
• Air for Combustion and Ventilation (International Fuel Gas Code / International Residential Code Chapter 24, Fuel Gas), International Code Council: https://codes.iccsafe.org/content/IFGC2018/chapter-5-chimneys-and-vents