Does running your gas fireplace in winter cost you energy?

According to the 2007 NRCan Survey of Household Energy Use, almost a quarter of all homes in Canada have a gas-burning fireplace. When a fireplace is operated in close proximity to a house’s central thermostat, it can cause the setpoint temperature of the thermostat to be satisfied and furnace operation will be reduced. As a result, the fireplace ends up essentially replacing the furnace as the main source of heat in the home. Unfortunately, not only is the fireplace usually less efficient than the furnace, but many gas fireplaces only direct heat to the room that they are located in – and can leave other rooms cooler in the process.

During the past two winters, CCHT researchers have used the twin houses to measure the impact of operating a gas fireplace on energy consumption and on room temperatures. Project results show that operating the fireplace for 6 hours in the evening required 144 MJ of natural gas per day for the fireplace. It reduced furnace gas consumption by 40%, and resulted in an average increase in total energy consumption for heating of 36 MJ/day (12.5%) during the experiment. In addition, the temperature in the second floor bedroom, furthest away from the fireplace, dropped by up to 2°C in the evening.

In another experiment, the fireplace was controlled 24 hours per day by a dedicated thermostat, set 2°C above the house setpoint temperature during the experiment. Under thermostat control, the fireplace consumed 249 MJ of natural gas per day, on average, and reduced furnace natural gas consumption by 59%. This resulted in an average increase in total heating system energy consumption (for both furnace and fireplace) of 38 MJ/day (9.8%). Because of the near continuous operation of the fireplace, temperatures in the bedrooms on the second floor of the house were 1 to 2°C cooler, on average, than the rest of the house.

Consumption with and without fireplace operation on sample winter days is shown in the figure below. The pilot light alone consumed 38 MJ/day (equivalent to 440 watts operated continuously), when the fireplace was not in operation. However, the pilot light released some heat into the home and reduced furnace operation, resulting in an average increase of 18 MJ/day (5.0%) in total energy consumption for heating. While other models of fireplace and other house layouts would likely give diff erent results, this experiment highlights the potential for a gas fireplace to increase home energy use, and reduce room temperatures.

This project was funded by Canada Mortgage and Housing Corporation. The full project report is available in our project section.

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