Are high efficiency gas water heaters worth buying?
A high efficiency gas water heater captures more of the fuel's heat than a standard tank, through a condensing heat exchanger, sealed combustion or on-demand firing. It typically costs more to buy and install, so the payback depends on how much hot water the household uses and what gas costs locally.
What counts as a high efficiency gas water heater?
Three designs are sold as high efficiency.
- Condensing storage tank. A second heat exchanger pulls heat from the exhaust, and the cooled gases leave through plastic pipe with a condensate drain.
- Power-vent or direct-vent tank. A fan or sealed system moves exhaust outside and draws combustion air from outside the house. Efficiency gains are smaller than with condensing, but the unit is safer around house air.
- Condensing tankless. Heats water on demand and condenses its exhaust. It saves standby loss as well. See tank versus tankless.
A standard atmospheric-vent tank is the baseline they are compared with. It loses heat up the chimney and through the tank walls whenever it is idle.
How do you read the efficiency rating?
Look for the Uniform Energy Factor, or the older energy factor, on the label and in the manufacturer's data. A higher number means more of the fuel ends up in the water over a typical day. Compare the number across models of similar size, and check whether the unit is certified under a recognized energy-efficiency program. Natural Resources Canada and the Government of Canada energy-efficiency pages list the labelling and certification programs.
A rating is a lab result. Real savings depend on the volume of hot water used, the incoming water temperature and the standby loss of the tank. Households with a small draw see little gain from a premium unit, while a busy home sees more. Our look at hot water tank sizing helps you judge your own use.
What venting and installation changes should you expect?
High efficiency units commonly need more than a swap. Condensing models require plastic venting and a floor drain or condensate pump nearby. Power-vent models need an electrical outlet and a wall or roof penetration for the vent pipe. A tankless gas unit may need a larger gas line and a bigger vent. Combustion air may also need to come from outdoors.
Gas work needs a licensed gas fitter, and a permit may be required, so check with the local authority or installer. Quotes should list venting, gas line and electrical work as separate lines, as discussed in hot water tank replacement. The installation costs can outweigh a small efficiency gain, which is why an apples-to-apples quote matters.
When does the extra cost pay back?
A simple way to think about it: extra purchase and installation cost divided by yearly gas savings gives a payback in years. The yearly savings are the energy the new unit saves multiplied by your gas price. Both numbers come from your quotes, your bills and the unit's rating, so use your own rather than a general figure. Prices vary by region and year.
Beyond gas, think about the long run. If you expect to switch to electric heating or a heat pump water heater in the next several years, a premium gas unit may never pay back. See heat pump water heaters in Canada and natural gas versus electric heating. Rebates for efficient water heaters change often, so check the provincial energy ministry and your gas utility before buying.
Quick answers
Is a condensing gas water heater worth it?
It can be for households with high hot water use and a drain and vent route that are easy to install. For small households the extra cost may take years to repay.
Do high efficiency gas water heaters need special venting?
Yes. Condensing units use plastic venting and a condensate drain, and power-vent units need electricity and a sealed vent pipe.
What is the Uniform Energy Factor?
It is a rating of how efficiently a water heater turns energy into hot water over a standard test day. Higher is better, and the figure appears on the label.