If you are adding on to a Burlington home this summer (a kitchen extension, a primary-suite addition over the garage, a sunroom and great-room build off the back) the framing portion of the quote is going to read predictably from one bid to the next. The electrical scope is where the variation lives, and homeowners almost always underestimate it. Here is how we think about an addition's electrical from the design stage forward, and where the dollars actually go.
The framing is repeatable. The electrical is not.
Two 600-square-foot additions in two Burlington neighbourhoods can read identically on the architectural drawings and have completely different electrical scopes. The variables: where the existing panel sits, how loaded that panel already is, whether the existing service has spare capacity, whether the addition includes a kitchen or bathroom or just bedroom and living space, how the HVAC is being handled, and whether the homeowner is planning for an EV charger, heat pump, or hot tub in the next ten years that the new wiring should accommodate.
The framer's quote can come in within $5,000 of every other framer in town. The electrical quote, even with everyone working from the same drawings, can vary by tens of thousands depending on what the contractor is including. The reason is that more than half of the cost variability is about the existing service capacity, the subpanel question, and what the addition makes us redo in the existing house. None of those costs are visible on the architectural drawings.
The service-capacity question: first conversation
Before any wire gets pulled, we do a load calculation on the existing house plus the proposed addition. Real demand calc, not a rule of thumb — installed loads at OESC demand factors, continuous loads at the 125% multiplier, and the new loads from the addition.
The outcomes are usually one of three:
- 200A panel with comfortable headroom. The new circuits land in the existing panel. No service work. Cleanest case.
- 200A panel that is full of breakers but has demand-side capacity. The new circuits land on a subpanel fed from the main, with the subpanel located in the addition. Adds the feeder run, the subpanel itself, and a slot in the main panel for the feeder breaker — but does not require utility-side work.
- 100A panel or 200A panel at demand limit. The conversation opens to a service upgrade as part of the project. New meter base, new service-entrance conductors, new main panel. Adds a full day on site and a utility-coordinated power-off.
This is the single conversation that drives the largest cost swing on the entire project. The customers who get it wrong are the ones who took a flat-rate quote from a contractor who never did a load calc — and then found out at rough-in that the panel cannot accept the new circuits.
Subpanel placement: get it right at framing
If the addition is going to need a subpanel (and most 400-square-foot-plus additions do), the placement of that subpanel during framing will save thousands later. The right spot has three properties:
- Accessible. Not behind a finished wall, not in a closet that will be drywalled and forgotten, not where the laundry sink will be installed in front of it. The OESC requires working space in front of every panel.
- Short feeder run. The shorter the run from the main panel to the subpanel, the smaller the feeder conductor needs to be for voltage drop. A 30-metre feeder run drives the conductor up in size; a 12-metre run is much cheaper.
- Near the heavy loads. Kitchen, bathroom, HVAC equipment, EV charger location. Branch circuit runs from the subpanel out to the loads should be short.
We sit down with the framer or the general contractor at the framing stage and locate the subpanel before drywall. A subpanel that gets relocated after drywall is going up costs more than the panel itself.
Fixture count: bigger than you think
A 600-square-foot addition reads small on the drawings. The fixture count rarely does. A typical kitchen-and-great-room addition that we wire might include:
- 20-30 pot lights on multiple zones
- Under-cabinet lighting in the kitchen — separate transformer or driver, separate switch
- Pendants over the island — separate dimmer
- 4-6 wall sconces and decorative fixtures
- Exterior fixtures on the new walls — soffit pots, wall packs, motion lights
- Ceiling fan rough-ins on the great-room and primary suite
- 15-25 receptacles depending on layout — kitchen counter circuits, island, dining, living, primary
- Dedicated 240V for range, dryer, hot tub, future EV charger if applicable
- HVAC disconnects, electric baseboard or in-floor heat if specified
- Smoke and CO interconnect tied back to the existing house system
- Low-voltage rough-in for Cat6, coax, AV, security
That count is what drives the labour line on the quote. A contractor who is quoting a flat rate for "electrical on the addition" without itemizing the fixture count is either generous (they are eating the variance) or about to surprise you on the change-order side.
Low-voltage rough-in: cheap now, expensive later
Pull the Cat6, the speaker wire, the conduit sleeves to the exterior security camera locations, and a conduit run to the EV-charger location before drywall. Every one of those is a tenth of the cost of doing it after the addition is finished. We pull the low-voltage rough-in as part of the addition's electrical scope on most jobs, and it pays back the first time the homeowner adds something that needs the cabling.
What we routinely rough in on a Burlington addition:
- Cat6 to every major room — corner of the living room, primary suite, office, kitchen island
- Conduit sleeve from the basement or attic to the panel for future smart-home gear
- Camera locations at exterior soffits with power and Cat6
- EV charger conduit run from the panel to the garage wall — even if the charger is not going in this year
- Speaker wire to ceiling pre-blocks in the great room and primary suite
What the inspector will catch
The ESA inspection on an addition is on the rough-in and on the final. The findings that come up most often:
- Box fill calculations — too many conductors crammed into a box
- Tamper-resistant receptacles missing in dwelling-unit locations
- Smoke and CO interconnect not tied back to the existing house
- Bathroom fans not on their own circuit or sharing GFCI in a way that drops the lighting on a trip
- AFCI protection missing on bedroom circuits in the new construction
- Bonding of metal water lines and gas lines where the addition introduces a new branch
We design around these from day one. The customers we end up rescuing are the ones who hired the framer's friend to do the rough-in.
Coordinating with the rest of the trades
An addition is the most-coordinated-trade job in residential work. The rough-in week has the framer wrapping up, the plumber running supply and DWV, the HVAC contractor pulling ductwork, and us pulling wire. The order matters — duct runs that block planned wire paths, plumbing that ends up in front of a planned receptacle box, fireplace gas runs that turn into "where do we route the conductor now?" conversations. We walk the framing with the GC before any wire goes in and resolve the conflicts at the chalk line, not at the inspection.
When to call us
If you are planning an addition in Burlington, Waterdown, Oakville, or anywhere in our service area, talk to us at the design stage — not at the rough-in stage. We do a free pre-design load calc on the existing house, we walk the architectural drawings, and we tell you whether the addition triggers a service upgrade or whether the existing panel will carry the new load. Request a design-stage consult. Spending an hour with us before the framer starts is the cheapest hour you will spend on the project.