Basement apartments are the GTA's favourite mortgage helper, and electrical is one of the two big-ticket trades in making one legal (fire separation is the other). Here's where the money actually goes.
Why a second unit costs double a rec room
A standard basement finish — pot lights, outlets, a bathroom fan — runs $3,500–$7,000. A legal second unit layers code requirements on top: a kitchen with its own dedicated 20A small-appliance circuits, fridge circuit, and range or cooktop feed; interconnected smoke and CO alarms wired so that an alarm in either unit sounds in both (a strict Ontario Building Code requirement for second units); egress lighting; bathroom and laundry circuits; and usually a sub-panel so the tenant has their own breakers. Stack it up and $7,000–$15,000 is the honest range for the electrical scope alone.
The single most common surprise is service capacity. Two kitchens, two laundry setups, and any electric heating routinely push the load calculation past what a 100-amp service supports, which adds a 200A panel upgrade to the budget. We run the load calculation at the estimate stage specifically so this surprise happens on paper, not mid-construction.
Metering: three options, decide early
Most landlords include hydro in the rent — simplest and cheapest, no extra equipment. A full separate utility meter gives the tenant their own hydro account but costs $2,000–$4,000 in electrical work plus utility coordination. Private sub-metering (a check-meter you read yourself, billing the tenant per the lease) lands in between. The choice changes how the unit's feeder is wired, so make it before rough-in, not after drywall.
Permits, inspections, and doing it in the right order
A legal second unit involves a municipal building permit, and the electrical work needs its own ESA notification with inspections at rough-in and final — the building inspector will ask for the ESA paperwork. The sequence that avoids re-work: load calculation and design first, building permit, electrical rough-in inspection before insulation and drywall, then final. We coordinate directly with your contractor and the interconnected alarm requirements that trip up most DIY conversions.
Renting out an un-permitted unit risks insurance denial and municipal orders — the $10,000 done right protects the $200,000 asset. Call 416-837-4038 for a free site visit; we'll give you the load calculation and an itemized quote so you can budget the whole conversion accurately.