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Advanced Plumbing and Rooter Service

231 Market Place, Suite 540
San Ramon, CA 94583

Phone: 925-383-6100

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Close-up of woman's hand pressing a button on a residential gas water heater

Types of Gas Water Heaters | 4 Common Types

Do you want a water heater solution that both saves you money and saves the environment? A gas water heater could provide the ideal solution. Gas water heaters cost less upfront and produce 25-33% less greenhouse gas emissions than electric heaters. When you choose a tankless gas water heater you can save even more, while still enjoying an endless hot water supply. Understanding the differences between the four most common types of gas water heaters can help you choose the right one for your home.


A conventional gas heater looks just like an electric tank water heater and works in a similar way.

Capacity: Conventional tank gas heaters consist of a tank that can hold between 20 and 120 gallons of water that can be stored hot and is available for use.

Operation: Cold water is drawn to the bottom of the tank where it is heated and then rises to the top. A gas burner heats the water at the bottom, and the tank stores the hot water until it is used.

Efficiency: Conventional gas water heaters are simple and relatively inexpensive. They can recover hot water 2-3 times faster than an electric system. However, storage-style water heaters are generally less efficient than on demand systems as there can be energy losses during the water storage time.

Gas water heater with digital control panel.

Gas Tankless Water Heaters

Tankless gas water heaters rapidly heat water as it flows through the unit. Because they don’t store hot water, they are very small and can even be hung on a wall.

Capacity: Tankless systems work in terms of flow rate rather than capacity. This is based on how many gallons of hot water they produce per minute. Flow rates are usually 2-5 gallons per minute, and gas tankless heaters produce higher flow rates than electric.

Operation: When the hot outlet is opened, cold water flows through the unit and is heated by a gas burner for instant hot water.

Efficiency: Tankless water heaters are usually about 80% efficient, which is 24-34% more efficient than tank-style heaters.

Direct Vent Gas Water Heaters

Direct vent water heaters draw in air from outside the home and convey exhaust gases directly outside as well. This is different to regular ‘atmospheric vents’ which only use air from inside the room that contains the water heater. Direct venting ensures a supply of fresh air for the gas heater and prevents ‘back drafting’. Back drafting is where combustion gases flow out of the vent rather than fresh air being pulled in. This can lead to deadly carbon monoxide production around the water heater and into the house. This could lead to a very dangerous situation or even death.

Regular atmospheric vents also produce a net negative effect drawing air out of the home. On the other hand, direct vents keep the air in the home neutral and balanced. This is done by providing a fresh air supply for combustion while effectively removing all exhaust gases from the home. Direct vents rely on the hot exhaust rising to be taken out of the home, so don’t require any power for operation either.

Power Vent Gas Water Heaters

A power vent works in a similar way to a direct vent, drawing fresh air in from outside and releasing exhaust directly outside. The difference with a power vent is that it uses a powered fan to facilitate the removal of gases from the vent. This means that a power vent has to use some electricity to function. If you don’t have access to a chimney or vertical vent, a power vent may be the better alternative.

The Gas Alternative: Electric Water Heaters

Like gas water heaters, electric water heaters are available in both tank and tankless varieties. They work in a similar manner to a gas water heater, except that they use an electric heating element instead of a gas burner to heat the water. In general, gas powered water heaters are more efficient than electric powered water heaters.

While gas powered water heaters can save you money by providing the most efficient option, there are a lot of advantages to an electric water heater.

  • They do not have the danger of exploding due to a gas leak.
  • Installation is easier
  • The tank requires less space
  • No pilot light
  • You can put them on a timer