A heat pump for a garden suite or secondary suite is usually the simplest way to heat it well: one small ductless unit can heat and cool an open suite, and it gives the suite its own thermostat. The catch is the building code. A suite is a separate dwelling unit, and BC's rules on shared heating and ducts shape which system you can use. This guide covers those rules, sizing small spaces, running costs and rebates.
Does a secondary suite need its own heating system in BC?
The BC Building Code treats a secondary suite as its own dwelling unit, and the heating rules exist mainly to stop smoke spreading between units in a fire. Here is how two building departments describe the requirements:
- Shared systems need smoke control. Saanich's secondary suite code handout says the ideal solution is a separate ventilation system for the suite, and that if a heating and ventilation system serves more than one dwelling unit, it must be designed to stop circulating smoke on a signal from a duct-type smoke detector. Ducts that pass through the fire separation, with openings on both sides, need fire dampers.
- Each unit needs its own temperature control. The City of Prince George's 2024 building bulletin reads the 2024 BC Building Code as requiring new secondary suites (from January 1, 2024) to have separate heating with separate temperature controls for the main home and the suite. It lists acceptable ways to do it, including separate systems, separately controlled radiant zones, or a single forced-air furnace with an in-duct smoke alarm plus a separate heat source controlled in the suite.
Municipalities word this differently, and the rules for new suites are stricter than for legalizing an existing one. Confirm with your own building department before you choose a system.
Heat pump options for a garden suite or secondary suite
| Option | Best for | Code and comfort notes |
|---|---|---|
| Single-zone ductless (one head) | Open-plan suites and studios | Separate from the house; simplest and usually the lowest cost. Bedrooms with doors closed may run cooler. |
| Multi-zone ductless (two heads, one outdoor unit) | One or two bedroom suites | Heats a closed bedroom properly. The outdoor unit can serve only the suite, keeping the systems separate. |
| Ducted mini-split (small air handler) | Garden suites designed with a bulkhead | Ducts serve the suite only. Quiet and hidden; needs space planned at design. |
| Extending the main house's ducted heat pump | Rarely the right answer | Shared ducts trigger smoke detector shutdown and fire damper requirements, and the suite still needs its own control. |
| Heat pump plus electric baseboard in bedrooms | Tight budgets | Heat pump covers the main space; small baseboards cover closed rooms. Higher running cost in those rooms. |
For the wider comparison, see our ducted vs ductless heat pump guide and our ductless mini-split guide for Victoria.
How to size a heat pump for a small suite
Suites are easy to oversize, because square-footage rules of thumb were built for whole, older houses. An oversized unit short-cycles, dries the air poorly in summer and wastes energy.
- Work out the real heat loss. A new garden suite built to Step Code is airtight and loses little heat. A basement suite gains warmth from the house above. Both need less than square footage suggests.
- Choose the smallest variable-speed unit that covers the design load, and check how low it can turn down, not just its maximum output.
- Place the head where air can reach the whole space, usually high on the wall facing down the longest open run.
- Plan for closed bedrooms. Either a second head or a small backup heater in the bedroom.
- Think about noise. Keep the outdoor unit away from the suite's and neighbours' bedroom windows.
Our guide to what size heat pump you need explains BTUs and heads.
Garden suites: new-build rules apply
A detached garden suite is a new building, so it gets its own heating by definition and must meet the BC Energy Step Code level your municipality sets. In Langford and Colwood, new houses also have to meet Emissions Level 4 of the Zero Carbon Step Code, which means electric heating and hot water; Colwood has required this since March 2024 and Langford from building permit applications on December 1, 2026. Confirm how your municipality applies these rules to a garden suite. Our guide to heat pumps for Westshore new builds covers the details. The overall cost and planning of a suite project, beyond the heating, is a separate question for your builder; this guide covers only the heating system.
What does it cost to heat a suite with a heat pump?
For scale, Natural Resources Canada lists about 30 GJ of yearly heat for a 1,000 sq ft inside-unit townhouse in Victoria. Our heat pump operating cost guide works that out to roughly $390 a year at a seasonal COP of 3.0 and BC Hydro's 14.08 cent Step 2 rate. A smaller or newer suite should come in under that. Electric baseboards for the same heat would cost about three times as much.
Who pays depends on metering. If the suite shares the house's BC Hydro meter, the suite's heating lands on the owner's bill, and a separate thermostat at least lets the tenant control comfort. If the suite has its own meter, the tenant pays for what they use.
Can you get a rebate for a suite heat pump?
Possibly, for an existing suite. The CleanBC Better Homes Home Renovation Rebate Program lists a secondary suite in a single-family home as eligible where the home and suite are individually metered. The standard heat pump rebate (up to $4,000 whole home or $1,500 partial) is for electrically heated homes: the heat pump must replace a primary electric heating system such as baseboards. Homes must be at least 12 months old, so a brand-new garden suite does not qualify. BC Hydro's bonus of up to $1,000 also needs the install completed, invoiced and paid by October 31, 2026. Check your situation in the heat pump rebate checker or our rebate summary.
Adding or upgrading a suite? Get a free estimate for suite heating, or see our heat pump services.