Buildings
Overview
Building emissions increased by 1.7% or 0.4 megatonnes in 2024.
Building emissions come from two sources: from natural gas combustion onsite for space and water heating, and those associated with the electricity consumed in a building. Natural gas used for space and water heating generates roughly 82% of total building emissions.
In 2024, natural gas emissions declined 2.7% across the GTHA. However, when normalizing the data to remove the impact of weather, that decline becomes just 0.8%, indicating that the reduction in natural gas emissions was largely due to a milder winter. Electricity emissions on the other hand increased 28% because of the increasing carbon intensity of the provincial electricity grid.
Buildings remain the highest-emitting sector in Halton, Toronto, and Peel. Per capita building emissions range from a low of 2.4 tonnes of carbon per person in Durham to a high of 5.1 tonnes of carbon per person in Hamilton. As our region continues to grow, building retrofits and deep energy efficiency improvements are needed to achieve and sustain significant annual emissions reductions.
Building emissions performance standards (BEPS) are a key policy tool for improving the performance of existing buildings by limiting operational carbon emissions. They typically mandate environmental performance targets that become stricter over time, continuously driving improvement across the existing building stock.
In addition to reducing emissions, BEPS also creates local green jobs, drives demand for retrofits, and leads to healthier homes. As decarbonizing the existing building stock is critical to achieving net zero, TAF recommends all GTHA municipalities develop and implement BEPS in their jurisdictions.
Scope 3 Embodied Carbon: Together, production of concrete and steel are responsible for nearly half of total embodied carbon emissions in buildings. A TAF-funded study benchmarked the embodied emissions of building materials, reporting that the average annual embodied emissions of all new low-rise homes built in the GTHA is 0.84 MtCO2eq. Another TAF-funded study showed that high-rise building materials account for 465 kgCO2eq/m2, totaling 1.6 MtCO2eq annually in the GTHA. Adding these two sectors together means that the GTHA’s total embodied emissions in new buildings are at least 2.5 MtCO2eq.
Natural Gas
Natural gas emissions decreased by 2.7% in 2024, reaching 20.4 megatonnes.
"Natural gas," also known as methane or fossil gas, is largely consumed onsite for space and water heating and continues to be the major contributor to building emissions.
Natural gas emissions decreased by 2.7% in 2024, reaching 20.4 megatonnes. When normalized to account for weather variability, however, emissions decreased by only 0.8%. This indicates that much of the reduction in natural gas emissions observed in 2024 was attributable to a milder winter. Broken down by customer class, the residential sector saw a 3.2% decrease in weather normalized gas emissions while the industrial sector increased 2.9% and the commercial sector decreased 0.1%.
The largest increase in gas consumption occurred among industrial customers in the Town of Halton Hills, rising by 16%. The number of industrial customers in Halton Hills also rose by two. However, given the limited data available, it is not possible to determine whether the increase in consumption was driven primarily by one or both new customers, or whether it was more evenly distributed across multiple existing customers.
Normalized for weather and population, natural gas emissions decreased by 4.8% across the GTHA, from 2.88 to 2.74 tonnes per person.
Scope 3 Fugitive Methane: TAF reports on Scope 3 fugitive methane that leaks from extraction, fracking, pipelines, and distribution, the full life cycle of natural gas. Including fugitive methane demonstrates that natural gas combustion emissions are 30% higher than typically reported.
Ignoring this important source of upstream emissions can undermine climate action priorities, particularly where natural gas is marketed as a “clean” fuel source.
Electricity
Electricity emissions increased by 28% in 2024, rising from 3.5 to 4.5 megatonnes.
This continued a steady upward trend that began in 2019, with emissions increasing by more than 150% over that span. Electricity emissions are now the highest since 2015, when the last of the province’s coal-fired units were still being phased out.
Electricity consumption in the GTHA rose by 2.4% in 2024, reaching 60.3 terawatt hours. Consumption has remained largely unchanged over the past decade, with 2024 consumption being only 2.2% higher than in 2015.
Electricity Demand: Electricity demand in Ontario is projected to rise by 75% between now and 2050, driven primarily by the rapid growth of energy-intensive data centres needed to support the proliferation of artificial intelligence.
Consequently, it is essential that data centres consider all cost-effective measures for reducing their overall demand on the electricity grid, including behind-the-meter generation, battery storage, waste heat reuse, and demand response.
Meeting residual electricity demand with non-emitting resources will be key to preserving Ontario’s clean grid advantage.
See Electricity Grid
IESO and NIR Discrepancies
In the past, TAF noted discrepancies in the electricity generation from natural gas combustion reported by IESO and NIR, beginning in 2020. We flagged this to Environment and Climate Change Canada, and they have since resolved the cause of the discrepancy and updated their figures. There is now close alignment between the generation reported by IESO and NIR, as shown in the table below. TAF uses IESO electricity generation data in this inventory.
NIR and IESO Reported Generation
Electricity generation from natural gas combustion reported by IESO and NIR
2020 | 2021 | 2022 | 2023 | 2024 | |
|---|---|---|---|---|---|
IESO | 35 | 43 | 49 | 59 | 73 |
NIR | 37 | 43 | 49 | 59 | -- |
Difference | 6% | 0% | 0% | 0% | –– |
TAF recently published updated Ontario Electricity Emissions Factors and Guidelines to support best practices in greenhouse gas quantification. The update is based on available data and consultation with other experts and stakeholders and should be used to plan climate strategies as accurately as possible.