Summer Cooling Savings in Ontario: Stay Comfortable for Less

Ontario summers have become hotter and more humid, and air conditioning is now standard in most homes. Cooling usually costs less over a year than heating, but it is concentrated in the most expensive electricity hours, and a heat wave can make a bill jump. With smart settings, shading and basic maintenance, most homes can stay comfortable for noticeably less.

Know when electricity costs the most

Summer Regulated Price Plan hours (1 May to 31 October), using prices that took effect 1 November 2026:

Plan	Summer weekday hours	Commodity price
TOU on-peak	11 a.m.–5 p.m.	18.9¢/kWh
TOU mid-peak	7–11 a.m. and 5–7 p.m.	14.6¢/kWh
TOU off-peak	7 p.m.–7 a.m.; weekends and holidays all day	9.1¢/kWh
ULO ultra-low overnight	Every day 11 p.m.–7 a.m.	3.7¢/kWh
ULO on-peak	Weekdays 4–9 p.m.	37.7¢/kWh
Tiered	600 kWh/month threshold in summer	11.2¢ (Tier 1), 13.2¢ (Tier 2)

Note that the Tiered threshold drops to 600 kWh a month in summer, so homes running central air often move into Tier 2. If you are on ULO, a hot weekday afternoon and evening from 4 to 9 p.m. can be very expensive. Compare options in our electricity price plan calculator.

Thermostat settings that work

• Set cooling to about 24–26 °C when home, and a few degrees higher when away.
• As a rough rule, each 1 °C higher setpoint can save a few percent of cooling energy. The exact amount depends on your home and climate.
• Pre-cool on TOU: Lower the setpoint by 1–2 °C before on-peak starts (before 11 a.m. on TOU, or before 4 p.m. on ULO), then let the temperature drift up a little during peak. A well-insulated home holds the cool longer.
• Do not set the thermostat very low to "cool faster". Air conditioners cool at the same rate regardless.
• Use the "auto" fan setting rather than "on". Running the fan continuously can re-evaporate moisture from the coil and raise indoor humidity.

Block the heat before it gets in

Sunlight through windows is one of the largest summer heat sources.

Measure	Typical cost	Effect
Close blinds or curtains on east windows in the morning, west windows in the afternoon	Free	Reduces solar heat gain significantly
Exterior shades, awnings or solar screens	$100–$500+ per window	More effective than interior blinds because heat is stopped outside
Light-coloured or reflective interior blinds	$30–$150 per window	Helps on sunny sides
Shade trees on south and west sides	$100–$500 per tree (planting)	Long-term benefit; deciduous trees let winter sun through
Attic insulation and air sealing	Varies	Keeps upstairs bedrooms cooler; see our attic insulation guide

Control humidity

Ontario summers are humid. Lower humidity makes a higher temperature feel comfortable.

• Aim for roughly 40–55% relative humidity indoors in summer.
• Run bathroom fans during and after showers and use the range hood when cooking.
• In basements, use an ENERGY STAR dehumidifier set to about 50% and empty or drain it regularly.
• An oversized air conditioner cools quickly but removes less moisture, leaving a cold, clammy feel. Proper sizing matters; see our air conditioning buying guide.

Keep the equipment efficient

Task	When	Who
Replace or clean the furnace or air handler filter	Every 1–3 months in cooling season	Homeowner
Clear leaves, grass and debris from around the outdoor unit (about 60 cm / 2 ft)	Spring and as needed	Homeowner
Gently rinse the outdoor coil with a garden hose (power off)	Once a season	Homeowner
Check that the condensate drain is flowing	Spring	Homeowner
Professional tune-up: refrigerant charge, coil cleaning, electrical checks	Every one to two years	HVAC contractor (refrigerant work requires ODP certification)

Avoid planting shrubs or building enclosures tight around the outdoor unit; it needs airflow to work efficiently.

Caution: Refrigerant handling requires an Ozone Depletion Prevention (ODP) certificate. A system that needs repeated "top-ups" has a leak that should be found and repaired.

Use fans and ventilation wisely

• Ceiling fans let you raise the thermostat by roughly 1–2 °C with similar comfort. Turn them off when you leave the room, as fans cool people, not rooms.
• On cool nights (common in late spring and early fall), turn off the AC, open windows and use window fans to flush hot air out. Close up in the morning.
• Run heat- and moisture-producing appliances (dryers, dishwashers, ovens) in the evening, which also aligns with off-peak hours.

If you are replacing your air conditioner

If your central air conditioner is more than 15 years old, uses R-22 refrigerant, or needs a major repair, consider your options before it fails in a heat wave:

• A heat pump provides both cooling and heating. It usually costs more than a central AC to install, but it also takes on some or all of your heating. The Home Renovation Savings Program has offered incentives for qualifying cold-climate heat pumps installed by participating contractors with pre-approval. See our heat pumps guide.
• New equipment is rated by SEER2. Higher SEER2 means more efficient cooling.
• Newer equipment uses A2L refrigerants (such as R-454B or R-32) as the industry phases down R-410A.

A typical central AC replacement costs roughly $5,000–$9,000 installed (estimate).

Heat safety

Energy savings should never come at the expense of health. Extreme heat is dangerous, especially for older adults, young children and people with chronic conditions.

• During heat warnings, prioritize staying cool over cost.
• Check on elderly neighbours and relatives.
• Many Ontario municipalities open cooling centres during heat events; check your city's website.
• Never leave children or pets in parked vehicles.

Frequently asked questions

Is it cheaper to leave the AC on all day or turn it off?

For most homes, raising the setpoint by a few degrees when away saves energy. Turning it fully off on very hot days can leave the house hard to cool, so a moderate setback is usually the best balance.

Are portable air conditioners efficient?

They are usually less efficient than window units or ductless mini-splits. Dual-hose portable units perform better than single-hose models.

Should I close vents in unused rooms?

Closing a few is fine, but closing many can reduce airflow and harm system efficiency.

Do smart thermostats help with cooling?

Yes, if you use scheduling and pre-cooling features. They help most for households away during the day.