Where Do Heating Emissions Come From at Home?
Heating a house and its water accounts for well over half of household energy use in Canada, so it is a major source of residential emissions. How large depends on the fuel, the efficiency of the equipment and the building, and, for electric heat, the province's grid.
Why does home heating matter for emissions?
Canadian homes spend many months below comfortable indoor temperature, and space heating plus water heating usually make up well over half of household energy use. Where that energy comes from decides the emissions. Burning natural gas, heating oil or propane releases carbon dioxide at the point of use, while electricity releases it, if at all, at the power plant.
The national figures change each year and are published by the federal government in its inventories and energy-use tables. Look up the latest edition if you need the exact share instead of relying on a rounded statement.
Heating oil and propane have higher emissions per unit of heat than natural gas, while wood burned from sustainably managed sources is often counted as low-carbon in inventories, though smoke and fine particles remain a health concern.
How much does a gas furnace emit?
Natural gas gives off roughly 50 kg of carbon dioxide per gigajoule burned, a figure close to what the federal emission-factor tables give. As a worked example, assume a house needs 100 GJ of delivered heat a year and its furnace is 95 percent efficient. It burns about 105 GJ of gas, which comes to roughly 5.3 tonnes of CO2. Methane leakage upstream adds to the footprint, and is usually accounted for separately.
A lower-than-100 GJ load changes all of this proportionally, which is why reducing demand comes first; the method for finding the load is in home energy audit in Canada. Cost aspects of the same load are discussed in home heating costs in Alberta.
When does a heat pump beat a furnace on emissions?
It depends on the grid. Keep the same 100 GJ of heat and assume a seasonal COP of 2.5. The heat pump then uses 40 GJ of electricity, about 11,100 kWh. For its emissions to match the furnace's 5.3 tonnes, the grid would need to emit roughly 470 g of CO2 per kWh. Anything cleaner favours the heat pump, anything dirtier favours the furnace on this narrow measure. A higher COP moves the break-even upward.
Provincial grid intensities vary enormously, from nearly zero in provinces dominated by hydro to far higher in those that burn fossil fuels, and they also fall over time as generation changes. Look up the current provincial figure in the federal inventory before concluding anything. The operating-cost side of the same choice is covered in heat pump vs furnace in Canada and natural gas vs electric heating.
Seasonal COP is not a fixed figure. It falls on the coldest days and rises on mild ones, and it depends on the model, the installation and the temperature of the water or air the system must deliver. Use a measured or rated seasonal value from the installer, not a brochure maximum.
What about solar heat?
Solar thermal heat has almost no operating emissions once built, though manufacturing and installation carry some. The Drake Landing Solar Community supplied 97 percent of space heating from the sun by 2012 and 100 percent in the 2015-16 season (see the performance results page). Those results came from a specially built district system that has since been decommissioned, so the lesson is about what is physically possible rather than a ready option.
What cuts heating emissions fastest?
Usually the order is: reduce the load, choose cleaner supply, then manage how and when heat is used. Airtightness and insulation come first, with sequencing set out in home insulation upgrade priorities. Then compare the equipment options in renewable heating options in Canada. A smaller house load also makes any later equipment switch easier to size and cheaper to run.
Behaviour has a place too. Small changes in set-points and scheduling reduce the load a little, as covered in smart thermostat savings in Canada, but they are a modest lever next to envelope and equipment upgrades.
Quick answers
How much CO2 does a typical gas-heated home produce?
It varies widely with house size, climate and efficiency. As an illustration, a home needing 100 GJ of heat from a 95 percent furnace would emit roughly 5 tonnes of CO2 a year.
Do heat pumps always cut emissions?
Not always, but in most provinces they do. They cut emissions when the grid emits less than roughly 470 g CO2 per kWh at a seasonal COP of 2.5.
Where can I find my province's grid emission factor?
The federal government publishes electricity emission intensities by province in its national inventory reports and emission-factor tables.