The rule, and the loophole it closes
Section 21(1): a landlord "shall not at any time during a tenant's occupancy of a rental unit and before the day on which an order evicting the tenant is executed, withhold the reasonable supply of any vital service, care service or food that it is the landlord's obligation to supply under the tenancy agreement or deliberately interfere with the reasonable supply".
Section 21(2) deems the landlord to have withheld the service where the landlord owes another person for it, fails to pay, and the supplier withholds as a result. An unpaid gas bill is legally the same act as turning the gas off.
The prohibition runs until an eviction order is actually executed. A tenant who has been ordered out, or who has stopped paying rent, still gets heat and water.
Heat in a Toronto winter
Toronto Municipal Code Chapter 497, Heating, is sharper than anything in the Act and is enforced by the City rather than by the Board. Section 497-1.2 requires a landlord to ensure "a minimum air temperature of 21 degrees Celsius is maintained in all areas of the dwelling unit from October 1 in each year to May 15 in the following year". Those dates were changed by By-law 1395-2024, in force 30 April 2025 — a great deal of published advice still quotes the older range, so check the Code rather than a summary.
Two qualifiers sit with it. Section 497-1.2.B applies the requirement only to a dwelling unit that is normally heated at the landlord's expense. Section 497-1.2.C adds that where a unit is already at 21 degrees, the landlord is not required to operate a heating unit. Contravention is an offence carrying a fine of up to $100,000, and each day is a continuing offence of up to $10,000.
So a furnace failure in February is three problems at once: a section 20 repair obligation, a section 21 vital service, and a municipal standards violation with its own enforcement. It is never a routine ticket.
If heat cannot be restored the same day, supply temporary heaters and record that you did. The question afterwards is what you did in the gap, and "we were waiting for the part" is only an answer if something else was keeping the unit warm.
Air conditioning is not a vital service, but there is a rule
Section 36.1, added in 2023, lets a tenant install and use a window or portable air conditioner in a unit where the landlord does not supply air conditioning, unless the landlord prohibits it in prescribed circumstances.
The conditions are on the tenant: notify the landlord in writing before installing, do not damage the unit or the complex, and install it safely and securely. Where the landlord pays for the electricity, the tenant's notice must include what they know about the unit's energy efficiency and their anticipated usage, and the landlord may in prescribed circumstances charge a seasonal fee.
Practically: a tenant telling you they are putting in a window unit is complying with the Act, not asking permission. Log the notice and inspect the installation for safety rather than treating it as a dispute.
Planned interruptions
A planned shutoff to do work is not withholding a vital service, but it is an interference with reasonable enjoyment under section 22 if it is handled badly. Give written notice with the date and the hours, keep it short, and restore when you said you would.
Where the work requires entry into units, the shutoff notice does not replace the section 27 notice of entry. They are different notices and you need both.