Ontario · 16 local services · checked September 28, 2026

Home energy audits and home testing in London

London gets about 3,809 heating degree-days a year (a moderate heating season), 25% of its houses were built before 1961, and 25 NRCan-licensed service organizations list its postal codes. Pick a service for the local details.

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A Victorian red-brick semi-detached house with a front porch in autumn

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. More snow in the drawing means more heating degree-days: a longer, colder heating season. Sources: Statistics Canada 2021 Census (table 98-10-0233-01), NRCan HOT2000 climate data.

London at a glance

Climate

London gets about 3,809 heating degree-days a year, a measure of how much heating its climate needs, and its winter design temperature, the cold day heating systems are sized for, is −18.4°C. Those figures come from the climate data for London in HOT2000, the home-energy software Natural Resources Canada (NRCan) gives energy advisors. A moderate heating season with warm summers: fixes should cut heating bills and keep the house cool.

Housing

Of London's 119,295 houses (single-detached, semi-detached, row houses and duplexes), 25% were built before 1961 and 66% before 1991, according to the 2021 Census. The typical house dates from 1971–1980.

Heating

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).

Radon

Health Canada's 2012 survey found 1.8% of 109 homes tested in the Middlesex-London Health Unit health region above the guideline. The larger 2024 Cross-Canada survey reports 3.5% (1 in 29) of houses at or above the guideline for the London, ON (London CMA) metro area.

Great Lakes–St. Lawrence Southern Ontario and southern Quebec

What homes in London need

Cold winters and hot, humid summers: seal the attic, dry the basement, plan cooling.

This region has real winters and hot, humid summers, so bills come from both heating and cooling. Natural gas heats most Ontario homes, while most Quebec homes use low-cost electricity. An EnerGuide evaluation here should cover air sealing and the attic, cooling and dehumidification, and keeping the basement dry before insulating it.

In London: London's summers are hot and humid, with about 55 days a year at a humidex of 30 or more, and lake-effect snow can pile up in winter. Plan right-sized cooling and dehumidification, plus attic air sealing to prevent ice dams.

What drives bills and comfort here

  • Both seasons cost money: winters are cold, and summers bring 37 to 74 days a year with a humidex of 30 or more.
  • Gas heats 50% to 85% of homes in Ontario cities; in Quebec most homes use electric heat, and 16% already heat with heat pumps.
  • Electricity costs about 8.3¢/kWh in Montreal versus 14.4¢ in Ottawa and 15.6¢ in Toronto (April 2025), which shapes heat-pump savings.
  • Basement flooding is a growing cost: 2024 storms flooded basements from Toronto to Montreal, with insured losses in the billions.

Local risks to plan for

  • Two tornadoes touched down south of the city during the May 2022 derecho.
  • About 7 days a year with freezing rain or drizzle.
  • About 19 days a year with a humidex of 35 or more.
  • Radon: about 1 in 8 Ontario homes tested at or above the guideline in 2024.

What to check first, and why

  1. Seal air leaks and top up the attic

    Air sealing is still the first retrofit. In the snowier Ottawa–Montreal–Sherbrooke belt, a leaky, under-insulated attic also causes ice dams.

    Ask your energy advisor: Ask for a blower door test and attic inspection, and whether old vermiculite insulation needs testing before any attic work.

    Blower door testAttic inspectionAsbestos and vermiculite check

  2. Right-size cooling to control humidity

    In humid summers, an oversized air conditioner or heat pump cools quickly but shuts off before removing moisture, leaving rooms clammy. A heat pump replacing the air conditioner also covers much of the heating.

    Ask your energy advisor: Ask for a room-by-room heat-loss calculation and a duct and airflow check before replacing your air conditioner or furnace.

    Heat-loss calculationDuct leakage test

  3. Keep the basement dry before insulating

    Basements can be about 20% of heat loss, but insulating a damp basement from the inside can rot the new wall. Flash floods have hit Toronto and Montreal repeatedly.

    Ask your energy advisor: Ask the advisor to check grading, downspouts, foundation cracks and the sump, and to look for damp spots or white mineral stains.

    Mould and humidity check

  4. Test for radon

    About 1 in 6 homes in the Ottawa–Gatineau and Montreal areas tested at or above Health Canada's guideline in the 2024 survey; Kingston and Sherbrooke ranked among the highest municipalities.

    Ask your energy advisor: Run a 3-month test in the heating season, and retest after air sealing or basement work.

    Radon test

  5. Plan backup heat for power outages

    Recent ice storms and the May 2022 derecho windstorm each left hundreds of thousands of customers without power. Every heat-pump plan needs backup heat and a safe way through an outage.

    Ask your energy advisor: Ask how your home would stay warm in an outage, and keep baseboards or the furnace as backup when adding a heat pump.

Tests that matter most here

  • Blower door test Measures leakage (ACH50) and, with a thermal scan, finds where air gets in. Best timing: Any season; pair it with a thermal scan in winter.
  • Infrared (thermal) scan Shows missing insulation and air leaks as cold spots. Best timing: December to February, early morning or on an overcast day, with at least 10°C between inside and outside.
  • Heat-loss calculation Prevents oversized equipment that short-cycles and dehumidifies poorly, and is needed to choose the right heat pump. Best timing: Before replacing an air conditioner or furnace, based on the house after planned upgrades.
  • Radon test Moderate to high regional radon, and upgrades can change indoor levels. Best timing: At least 91 days, mostly in the heating season; retest after upgrades.
  • Combustion safety test In gas-heated homes, tightening can cause spillage from older furnaces and water heaters. Best timing: During the blower door visit.

Upgrades that usually pay off here

  1. Air sealing plus attic insulation. Usually the best envelope payback. Today's new-home attic minimum here is about R-49, a good target for older homes. Don't disturb old vermiculite insulation until it's tested for asbestos.
  2. Heat pump instead of a new air conditioner. One machine gives efficient cooling and most of the heating. In Ontario it often pairs with the gas furnace; in Quebec, baseboards can stay as backup. Choose a cold-climate model in colder cities such as Ottawa, Montreal and Sherbrooke.
  3. Basement insulation, once it's dry. A large heat-loss area. Fix water entry first, then insulate.
  4. Covered sump and better drainage. NRCan lists a covered sump among basement moisture fixes. Extending downspouts and sloping soil away from the house help keep storm water out.
  5. ERV for balanced ventilation. Brings in fresh air while recovering heat; NRCan suggests ERVs where cooling loads are high, as they are here.

Heating and cooling equipment

  • In colder cities such as Ottawa, Montreal and Sherbrooke, choose a cold-climate heat pump. Along Lakes Erie and Ontario, good variable-speed units cover most hours, with backup heat.
  • When a heat pump replaces the air conditioner, size it to balance heating and cooling; NRCan's guide caps cooling capacity at about 125% of the cooling load.
  • Electric backup (baseboards or strips) can run with the heat pump; a furnace in a hybrid system takes over instead of running at the same time.
  • For dehumidification, run the indoor fan on low in cooling mode, and size equipment so it runs long cycles.

Health and comfort

  • Damp basements: run a dehumidifier in summer, and keep indoor relative humidity below about 40% in cold weather to avoid condensation and mould.
  • Wildfire smoke can travel far: Ottawa's fine-particle level hit 511 on June 7, 2023 (normal is 4 to 11), and Montreal briefly had the world's worst air that month.
  • Heat: Ottawa reached a humidex of 47 in the 2018 Canada Day heat wave. Make sure at least one room can be kept cool.
  • Radon: about 1 in 6 homes across Central Canada tested at or above 200 Bq/m³ in the 2024 survey, though only about 1 in 22 in the Toronto area.

Common mistakes in this climate

  • Insulating a damp basement from the inside. Trapped moisture rots the new wall and feeds mould. Fix drainage and leaks first.
  • An oversized air conditioner or heat pump. It short-cycles, removes less humidity and wears out faster.
  • Tightening a gas-heated home without a safety test. Older gas appliances can spill exhaust into a tighter house. Ask for a combustion safety test.
  • Leaving hybrid controls on factory settings. The switchover between heat pump and furnace should match your gas and electricity prices. Ask how it's set.

When to book: Book the evaluation in winter (December to February) for clear thermal scans, and start a 3-month radon test in fall. Check the basement after spring thaw or heavy rain, and line up cooling work before summer.

Sources for this climate guide · checked October 26, 2026

Local service guides for London

Energy audits and tests

An energy advisor’s kit on a front-hall bench: infrared camera, pressure gauge with tubing, tape measure, headlamp and a floor sketch

Home energy audit

25 licensed organizations Companies NRCan licenses to do EnerGuide evaluations
A red blower-door panel with a large fan fitted into the front doorway of a brick bungalow, a pressure gauge on a stool inside

Blower door test

3,809 degree-days A moderate heating season
Hands holding an infrared camera aimed at a ceiling corner beside a frosty window; the screen shows a cold streak

Thermal imaging inspection

3,809 degree-days A moderate heating season
A kitchen table with a house floor plan, a laser measure, a tape measure and a laptop showing the plan

Heat loss calculation

Design temp −18.4°C The cold day heating is sized for
A duct-testing fan on a basement floor connected by flexible duct to a furnace, a pressure gauge hanging from a joist

Duct leakage testing

73% forced-air Share of homes with ducts that can leak
A gloved hand inserting a combustion analyzer probe into a furnace flue pipe in a basement

Combustion safety test

61% heat with gas Gas appliances need a venting check
A heat recovery ventilator on a basement wall with four insulated ducts running up between the joists

Ventilation and humidity assessment

24% built since 2001 Newer, tighter homes rely on fans or an HRV
Loose-fill insulation between attic joists, a yellow ruler showing its depth and frost on the roofing nails above

Attic insulation inspection

66% built before 1991 Older attics usually need more insulation
Utility bills and a phone showing a monthly energy-use chart on a kitchen table

Energy bill analysis

London Hydro Download 12 months of usage from your account

Home health tests

A small digital radon monitor on a bookshelf in a finished basement family room

Radon testing

3.5% at or above guideline (2024) Neighbours' results don't predict yours: test
A carbon monoxide alarm on an upstairs hallway wall outside the bedrooms at night

Carbon monoxide testing

Required by law
A moisture meter pressed into water-stained basement drywall, an air-sampling pump on a tripod nearby

Mould and indoor air quality testing

66% built before 1991 Older homes have more damp spots
A gloved hand holding a sealed sample bag above vermiculite insulation between attic joists

Asbestos and vermiculite testing

66% built before 1991 Common in materials until about 1990
A gloved hand swabbing layers of cracked old paint on a wooden window sill

Lead paint testing

25% built before 1961 Pre-1960 paint probably contains lead
Filling a water-sample bottle at a farmhouse kitchen tap with the aerator removed, snowy fields and a barn outside

Well water testing

Wells in some areas Only homes on private wells need it

For businesses and buildings

An auditor walking between rooftop heating and cooling units on a snowy commercial roof

Commercial energy audit

5 incentive programs

Who does energy evaluations in London

25 NRCan-licensed service organizations list London postal codes. See the list with phone numbers and coverage →

Ontario directory: verified advisor profiles for London, with prices where published.

City programs in London

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.

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.

Rebates and financing for London homes

Provincial · needs an evaluation Home Renovation Savings — Home Energy Assessment path Up to $10,000 per home ($5,000 if heated with Enbridge gas), including $600 back on your two assessments, for insulation, windows, air sealing and more — 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 National Heat Pump Rebate Announced October 8, 2026 and opening early 2027: up to $10,000 below the median income, $2,000 for other eligible homeowners Announced · opens 2027 Federal CMHC Eco Improvement premium refund A 25% energy-efficiency rebate on your CMHC mortgage insurance premium after $20,000 of energy renovations Open

Cities near London

Waterloo79 kmKitchener81 kmBrantford82 kmCambridge90 kmChatham-Kent98 kmGuelph102 km All 70 cities →

Sources

Checked September 28, 2026.

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