Gas Water Heaters
Review and Buying Tips

Searching for the best gas water heaters? Compare the tank-type vs. tankless heating, and explore the main components, differences, and advantages. How does it work? Who are the top manufacturers? Buying and sizing guide, installation and maintenance tips. Gas vs. electric. Venting options.

Highlights

Types

There are three types of gas-powered water heaters:

  • Storage tank
  • Tankless
  • Combination type (used for both heating the potable water and space)

Tank-type

Gas water heaterGas water heater

Gas water heaters with the storage tank-type are the most common and popular type in North America. The main purpose of the storage water tank is to hold the hot water, and it usually comes with the capacity from as low as 2 gallons to over 100 gallons. Heaters with the smaller capacity such as 20 gallons and less, are mainly designed for point-of-use service and a single application.

Larger ones are built for the whole house use and those with the capacity from 50 to 80 gallons are the most popular - they provide sufficient amount of hot water for families with 4-5 members. Most of the tank-type models are designed simple with the average energy efficiency, while the advanced models come with the condensing technology and have ultra-high energy factors. A great example is Vertex from AO Smith.

AO Smith Vertex (sold by Amazon) is the best tank-type from this manufacturer that comes with the efficiency of over 90%, stainless steel heat exchanger and environment-friendly gas burner.

Most of the available gas water heaters utilize natural gas, but if this fuel source is not available, the unit can be converted to use propane gas instead.

Water heating with the tank-type heaters is the most popular in North America, while tankless heaters are mainly used in Germany, Italy, France, UK, Japan...

How does it work

Gas tank-type water heaterGas tank-type water heater - Inside

Hot water is always ready in tank-type heaters. Even when there is no demand for hot water (i.e., the tap is open) a tank-type heater must cycle periodically to maintain the set temperature. If the water temperature inside the heater's tank drops below the set value, the thermostat sends the signal to the gas control valve to open.

Then, the pilot flame lights the gas inside the combustion chamber, which then heats the water. When small draws are made, the gas burner does not usually fire.

Cold water is coming into the tank through the inlet pipe or dip tube, while the hot water rises up and goes to the open hot water tap through the outlet pipe.

Products of gas combustion are then, traveling through the venting system out, either naturally or forced by the blower.

Selecting the right size of the gas water heater should be done by considering the family size and other factors. Keep in mind also that the tank has about 70% of the usable space, so if you have a 50-gallon gas model, the tank can store 35 gallons.

Where to use gas water heaters with the storage tank

Tank-type and gas-powered water heaters can be found in sizes from 20 gallons to over 100 gallons. These heaters can be used in residential, commercial applications, and manufactured or mobile homes.

The residential heater is usually installed in a garage, attic, basement or utility room, and it depends on the room space and installation requirements. Tank-type gas hot water heaters cannot be installed in the bathroom or bedrooms and must be installed indoor as close as possible to the outside wall or chimney.

Venting options

Based on how flue gases are vented out, gas hot water heaters are designed as atmospheric, direct, power or power-direct vented units. They must be installed per codes and manufacturer's instructions.

Each type is designed for different house type, and location of the unit has to take into account the type.

Atmospheric vented models are the most common type. The vent runs vertically, above the roof-line and are using the vertical standard B type vent or masonry chimney.

Direct vented (DV) heaters do not use the electrically powered blower and chimney. They have a sealed combustion chamber and two pipes; one for extracting gases out and one for the air intake, from the outside.

Power vented (PV) units utilize a blower to move the flue gases out. This type is more flexible than the atmospherically vented heaters, as the vent can run vertically or horizontally and through the roof or the wall. The heater can also be at the certain distance from the termination point, but it is more expensive.

Power direct vent models (PDV) are used in homes that lack sufficient air for gas combustion. Since the inside air cannot be used for combustion, the air is drawn from outside using the vent pipe while the electric blower moves the flue gases out. They are also used in homes that require flexible installation, such as when longer vents are required. The venting pipes can run either horizontally or vertically.

More about venting types, layout, problems and installation tips here.

Manufacturers

The most popular manufacturers of tank-type gas hot water heaters are:

Note: AO Smith, Rheem and Bradford White manufacturers from this list are the largest manufacturers in North America while other manufacturers or brands are their subsidiaries or re-brands.

Popular

Main components

When comparing the above brands, you will see that they have many similar parts. Of course, the quality varies. The elements shown below can be found in the majority of today's gas water heaters:

Tankless type gas water heaters

Rinnai tankless water heaterTankless

In the last decade or so, gas powered tankless water heaters are getting more and more on popularity. The main advantages are endless hot water, on-demand heating, small and compact size and wall mounted installation.

Tankless gas water heaters can provide hot water for any home size or application, but it depends on the model and installation options. They can work as the single unit where some brands such as Noritz NRC1111, can provide the high flow rate of 11 gallons per minute or function as the multi-system (some manufacturers offer features to connect up to 24 units into one system).

Tankless heaters are also using natural gas and propane (LPG) gas as the tank-type. These on-demand units are more energy-efficient than conventional tank-type heaters, as they don't have a standby heat loss. They produce fewer greenhouse gases, and that is why they are called "green."

More advanced gas water heaters are using condensing technology, which increases the energy efficiency to over 90% and provides significant savings. A great example is Rinnai RUR98. 

When you buy Rinnai RUR98 (sold on Amazon) you will get a superior device with the efficiency of 96%, the most innovative electronics, recirculation, Wi-Fi connectivity and more.

Tankless water heaters are much smaller than the above tank-type and are usually mounted on the wall. Instead of heating water that is stored inside the tank, they use an on-demand technology that utilizes heat exchangers, so water is delivered in endless supply when needed. Efficiency is much higher.

Main components

  • Heat exchanger - most of the tankless heaters have one exchanger while condensing have two
  • Power or direct venting
  • Gas burner
  • Gas valve
  • Electrodes for lighting
  • Electronic board
  • Control panel
  • Sensors (flow, temperature...)

Manufacturers

Popular

Tank vs. tankless

  • Water tank heaters are cheaper than tankless while installation and venting costs are lower.
  • Some tank-type units do not require electricity.
  • Flow rates are higher on storage tanks.
  • Tankless provides endless and fresh supply of hot water.
  • Tankless are smaller, wall mounted and do not occupy floor space. Some tankless models can be installed in the bathroom or kitchen.
  • Tankless have low operating costs.
  • Indoor and outdoor models are available.
  • Energy efficiency is higher on tankless.
  • An advanced electronic system for the precise temperature control and diagnostics.

More about tank vs. tankless here.

Gas vs. electric

  • Gas heats water faster.
  • Gas models are Energy Star compliant.
  • Gas heaters have lower operating costs.
  • Some gas models do not require electricity to operate.
  • Electric models are more straightforward and cheaper.
  • Electric units have lower installation costs.
  • Electric models are safer.
  • There is no venting in electric models.
  • Electric has higher energy efficiency but is not Energy Star.

Sizing tips

When you are choosing a gas water heater, it is essential to do proper sizing, so the unit meets the needs of the whole household. The size of the water heater (capacity in gallons) depends on the number of people in your home and how many applications are to be used at the same time.

Check the Energy Guide label of the gas water heater to determine the first-hour rating (FHR). It is essential to have the FHR number higher to get enough hot water during the peak hour. The first-hour rating is the measure of how much hot water the unit will deliver during the peak time.

If your family counts for 1-2 people, a 40-gal unit is sufficient. For 3-5 people, choose a 50-gal unit and for more people select a water heater with 60 and more gallons.

Use the sizing chart below to see how much water is used per application:

  • Shower - 10 gallons
  • Bath - 20 gallons
  • Dishwasher - 6 gallons
  • Washing machine - 7 gallons
  • Shaving - 2 gallons

Summary

When searching for the gas water heaters, the recommendation is to look for the high energy factor - EF, Energy Star approved models and high first-hour delivery or water flow rate (GPM). They save energy, do the work efficiently and provide savings with the lower consumption, government grants, and utility company rebates.

When comparing gas vs. electric, gas powered heaters are better solution as they heat water faster, have a higher recovery rate, cost less to operate and offer better selection of the products.

(updated 2019)

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