GHG emissions from utility data, and keeping ENERGY STAR Portfolio Manager in sync

Emissions reporting for buildings is arriving from several directions at once: Montreal's by-law discloses and rates emissions, Vancouver sets emissions limits, Toronto's reporting by-law is described by the City as the foundation for emissions performance standards, and lenders and investors ask for portfolio carbon figures. For most owners the underlying calculation is the same: consumption from utility data multiplied by an emission factor per commodity.

This article explains where the factors come from, what to watch for in the multiplication, how emissions appear in the VE-MAP monthly review and annual benchmark report, and how the same validated data is kept in sync with ENERGY STAR Portfolio Manager.

The calculation

Operational emissions from a building fall into two groups. Direct emissions come from fuel burned on site, mainly natural gas for heating and domestic hot water. Indirect emissions come from purchased electricity, and from district heating or cooling. Each is consumption times a factor:

• Natural gas: cubic metres times a combustion factor in grams of CO2 per cubic metre.
• Electricity: kWh times the grid intensity factor for the province, in grams of CO2e per kWh.
• District energy: the supplier's published factor per unit of heat or cooling delivered.

Where the factors come from

Environment and Climate Change Canada publishes emission factors and reference values drawn from Canada's National Inventory Report. That document lists, for example, an Ontario electricity consumption intensity of 30 g CO2e per kWh for 2023 and 2024 and 38 g for 2025, and a marketable natural gas factor for Ontario of 1,921 g CO2 per cubic metre. Two things follow. Grid factors change year to year, so an emissions trend must use the factor for each year, not one factor for all. And provincial factors differ enormously; the same building in Alberta and Quebec would show very different electricity emissions for identical consumption.

What to watch in the multiplication

• Consumption first. Every error in the consumption data, a doubled bill, a missing month, an adjusted rather than metered kWh, becomes an error in emissions. The validation checks run before any factor is applied.
• Calendar alignment. Annual emissions need calendar-year consumption, which needs a consistent reporting month rule.
• Units. Gas is billed in cubic metres in Ontario and sometimes shown in gigajoules elsewhere; factors are per cubic metre or per gigajoule and must match.
• Intensity denominators. Emissions per square metre is the comparable figure across buildings; the floor area must be the same one used for energy intensity and for Portfolio Manager.

Emissions in the monthly review and annual report

The monthly review shows a trailing twelve month donut of emissions by commodity beside the cost donut, and an emissions intensity indicator against the portfolio average and the Energy@Work average. The comparison is usually the first time a property team sees that gas, not electricity, dominates their emissions in Ontario, which changes the priority list: heating controls and envelope ahead of lighting. The annual benchmark report carries the year's totals and the ENERGY STAR data alongside.

A worked illustration with the ECCC factors above: a building using 1,000,000 kWh of Ontario electricity and 200,000 cubic metres of natural gas in 2024 would show roughly 30 tonnes CO2e from electricity (1,000,000 times 30 grams) and roughly 384 tonnes CO2 from gas (200,000 times 1,921 grams). The gas figure is more than ten times the electricity figure, and it will stay that way even as the electricity factor rises, which is the arithmetic behind the priority order. Emissions intensity per square metre lets a 40,000 square foot building and a 400,000 square foot building be compared on the same basis.

Keeping Portfolio Manager in sync

ENERGY STAR Portfolio Manager computes its own emissions and the score, which adjusts for weather and property use details, from the meter entries it holds. If those entries lag the bills or contain the errors above, the filed figures and your internal figures diverge, and someone has to explain the difference to a board or a regulator. The practical fix is to push validated consumption to Portfolio Manager every month rather than re-keying it every June.

1. Connect the Portfolio Manager account; the platform reads each property's profile, meters and metrics.
2. Map each building's commodities to Portfolio Manager meters (electricity in kWh; gas and water in cubic metres), creating a meter where none exists.
3. Preview the push: the rows and the exact data to be sent are shown for a chosen date range.
4. Confirm. The push reads what the meter already holds and skips overlapping periods, so re-running it adds only new months.
5. Pull the property back for the annual benchmark report, so the filed site EUI and score are printed beside the utility-based figures with the difference explained. See ENERGY STAR Portfolio Manager for Canadian multi-residential buildings.

Reporting programs that use these numbers

Ontario's EWRB filing and Toronto's by-law are energy and water programs, but Toronto's BEPS page describes the reporting requirement as the foundation for emissions standards. Montreal's by-law 21-042 discloses and rates emissions from energy data submitted through Portfolio Manager by June 30 each year. Vancouver's by-law sets emissions intensity limits for large commercial buildings from 2026, per the Institute for Market Transformation. The comparison is in building energy reporting rules in Toronto, Montreal and Vancouver.

FAQ

Should we use location-based or market-based electricity factors?

Location-based factors (the provincial grid average) are what public programs generally use and what the ECCC values above represent. Market-based accounting applies where an organization buys specific clean electricity products. Use location-based for reporting unless a program says otherwise, and keep the choice as a documented setting.

Do Green Button data include emissions?

No. Green Button carries consumption and billing data. Emissions are computed from it with the factors above.

Can VE-MAP produce our sustainability report's carbon figures?

It produces the building-level consumption and emissions with the factor set you choose, exported to PDF, Excel, Power BI or Portfolio Manager. How those roll into a corporate disclosure is your reporting framework's job. Details on the about page and the use cases page.