Ontario · Energy · checked September 28, 2026

Heat loss calculations in London

The heat loss calculation is how a heat pump or furnace gets sized for your house, and the key input is the design temperature: −18.4°C for London, from NRCan's HOT2000 climate data for London.

Get matched in London → The CSA F280 heat-loss calculation
A kitchen table with a house floor plan, a laser measure, a tape measure and a laptop showing the plan

Design temperature

−18.4°C

Heating degree-days

3,809

Standard

CSA F280

Typical cost

$150–$400 standalone

How London is built

London's houses by when they were built Ten house shapes, one for each tenth of London's 119,295 houses. Before 1961: 25%, 1961–1990: 41%, 1991–2000: 11%, 2001 or later: 24%. Older houses glow hotter.
  • Before 1961 25%
  • 1961–1990 41%
  • 1991–2000 11%
  • 2001 or later 24%
Each house stands for one in ten of London's 119,295 houses (single-detached, semi-detached, row and duplex), drawn by when it was built. The glow shows the usual pattern: older houses tend to be leakier and less insulated. Snowfall scales with heating degree-days. Sources: Statistics Canada 2021 Census (table 98-10-0233-01), NRCan HOT2000 climate data.

Why the design temperature matters in London

−18.4°C is the 28th-mildest design temperature of the 70 cities we cover. The F280 calculation works out how much heat each room loses on that design day, from the house's actual walls, windows, air leakage and ceiling insulation.

At −18.4°C, a cold-climate heat pump sized to the calculation can carry most of the season, and the number shows how much backup heat the coldest days need.

In the London area, 73% of households heat mainly with a forced-air furnace; natural gas is the main heating energy for 61% of households and electricity for 24% (Statistics Canada, 2023).

Why skipping it costs money

Contractors who size by square footage routinely oversize. An oversized heat pump costs more to buy, cycles on and off, dehumidifies poorly in summer and wears faster. An undersized one leans on backup heat. The F280 report is the evidence either way, and it's worth having before you compare quotes.

What it costs

About $150–$400 as a standalone calculation (a September 2026 planning range; quotes vary). Many energy advisors bundle it with an EnerGuide evaluation, which also gives the calculation measured air-leakage data instead of an assumption.

NRCan-licensed service organizations serving London

Many energy advisors also do room-by-room CSA F280 calculations for an extra fee; HVAC designers do them too. Ask for the F280 report itself, not just an equipment recommendation.

Only assessments from the seven HRSP-approved organizations qualify for the $600 Home Renovation Savings rebate and its assessment-path upgrade rebates; each listing below says whether it's one of them.

Source: NRCan list of licensed service organizations, checked September 28, 2026. Call to confirm your street is covered and ask about wait times.

Heat pump programs in London

Provincial · needs an evaluation Home Renovation Savings — Home Energy Assessment path Up to $10,000 per home for insulation, windows and air sealing, plus $600 back on your assessments — if the follow-up assessment is done by December 31, 2026 Open · deadline Provincial Home Renovation Savings — direct rebates (no assessment) Heat pumps up to $7,500 ($12,000 ground-source), solar with battery up to $10,000, plus attic, thermostat and appliance rebates — no assessment needed Open Federal CMHC Eco Improvement premium refund 25% back on your CMHC mortgage insurance premium after $20,000 of energy renovations Open Municipal BetterHomes London loan City of London program (FCM Green Municipal Fund-supported) with a free retrofit coach: loans up to $40,000 at a 2.5% fixed rate, terms up to 20 years, repaid through property taxes, with up to 50% of approved costs paid up front. The project must cut energy use by at least 25% (typically a $20,000-$30,000 investment); at least 80% of costs must be energy efficiency. For detached, semi, townhomes, duplexes and triplexes used as a full-time primary residence. Participants usually pay for the initial energy assessment ($500-$700) before financing approval; EnerGuide assessment costs are eligible for financing. Site updated Sept 2026. Municipal BetterHomes London income-qualified incentives Grants that do not have to be repaid, deducted from the loan balance after renovations. Paid on a sliding scale by energy savings: $2,500 at 25%, $3,000 at 30%, $4,000 at 40%, $5,000 at 50%, $6,000 at 60%, $7,500 at 75%, up to $10,000 at 100%. Household income must be under $95,000 for one person or under $115,000 for two to five people. Rental properties are not eligible.

Heat loss calculation in London: common questions

What design temperature is used for heat pump sizing in London?

NRCan's HOT2000 climate data gives −18.4°C for London. Your designer may use the building code's design value for London, which can differ slightly; ask which one the calculation uses.

How much does a heat loss calculation cost?

About $150–$400 standalone as a planning range; often less when bundled with an EnerGuide evaluation.

Who does F280 calculations in London?

Many of the 25 NRCan-licensed organizations serving London offer them, as do HVAC designers. Ask for the F280 report itself.

Do rebate programs require a heat loss calculation?

Requirements vary by program and change often. Even where it isn't required, it is the best protection against an oversized or undersized system.

Heat loss calculation near London

Heat loss calculation in Waterloo79 kmHeat loss calculation in Kitchener81 kmHeat loss calculation in Brantford82 kmHeat loss calculation in Cambridge90 kmHeat loss calculation in Chatham-Kent98 km All 70 cities →

Sources

Checked September 28, 2026. Census figures are for the municipality (Ontario); climate data is NRCan's HOT2000 station London (10 km away).

Get matched with a registered advisor in London

Tell us your postal code and what you’re planning. We’ll connect you with one licensed service organization serving your area. No spam, no shared lead lists.

Email us what you’re planning, your postal code and the type of building (a house, a duplex or triplex, or a larger multi-unit building) — we’ll reply with registered service organizations for your area and which rebates apply.

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