Load calculations

Electrical load calculations in Edmonton to size services and feeders, check room for EV chargers, heat pumps and renovations, and support permit applications.

Why load calculations matter

Every electrical service has a limit. A 100 amp house service, a 400 amp shop service or a large industrial supply can only deliver so much before the main breaker trips or equipment overheats. A load calculation tells you how close you are to that limit and what happens when you add something new.

In Edmonton, we see this question come up constantly as people add EV chargers, heat pumps, air conditioning, hot tubs, basement suites and shop equipment. In businesses, it comes up with new kitchen equipment, server rooms, process machinery and expansions.

How the calculation works

The Canadian Electrical Code sets out how to calculate the minimum service or feeder size, in Section 8. The method depends on the type of building: single homes, apartments, commercial and industrial occupancies each have their own approach.

The method does not simply add up every nameplate. Not everything runs at full power at the same time, so the code applies demand factors to arrive at a realistic figure. Large loads like heating, air conditioning, EV chargers and ranges are handled in specific ways.

For existing buildings, actual demand data from your utility can sometimes support the decision, depending on what the code and permit authority allow for your situation.

When the numbers do not fit

If the calculation shows you are over, there are usually several options:

• A service upgrade to a larger supply.
• Load management, such as an EV energy management system that pauses charging when other loads are high.
• Choosing more efficient equipment, such as a heat pump instead of added resistance heat, where it suits.
• Moving some loads to a separate supply in commercial settings.

We explain each option and what drives its cost, so you can pick the one that fits your plans and budget.

What you receive

You get a written summary of the loads, the calculation method, the result and our recommendations. Permit authorities often ask for a load calculation with service changes, EV chargers and larger renovations, and our summary is prepared to support that application.

Cost depends mostly on building size and complexity, the number of loads to inventory, and whether a site visit or meter data review is needed. Simple residential calculations are quick; commercial and industrial calculations take more time.

Common Edmonton scenarios

These are the situations where we run load calculations most often:

• A 1960s or 1970s bungalow with a 60 or 100 amp service adding an EV charger.
• A house switching from a gas furnace to a heat pump with electric backup heat.
• A basement suite with its own kitchen and laundry.
• A detached garage with a heater, welder and compressor.
• A restaurant moving into a unit built for retail.
• A shop adding new machinery or a second shift.

In each case, the answer is rarely just yes or no. The calculation shows how much room there is and which option, upgrade or load management, makes the most sense.

Questions we hear