Peak Demand Charges in Canada: What Happens When You Go Over

In Canada, commercial and industrial electricity bills have two parts: energy (kWh you consume) and demand (your highest measured kW or kVA in a billing interval). Going "over" does not trigger a fine — it resets the demand figure your utility bills you on, and in many tariffs that higher figure follows you for up to 11 more months through a ratchet clause.

Canadian utilities meter your average power over a short interval — commonly 15 minutes, 30 minutes in some tariffs — and bill the highest interval of the month as your billing demand. If your normal peak is 400 kW and one morning start-up pushes a single interval to 550 kW, you are billed for 550 kW that month at your tariff's $/kW rate, even though the surge lasted minutes. Nothing is switched off and no fine is issued; the line item simply grows. The extra cost of that one interval is (150 kW × your demand rate), repeated for every month the higher figure applies.

Demand rates vary widely by province and by rate class, so check the tariff sheet for your own account rather than assuming a national number. Broadly: Ontario large users are billed through Global Adjustment and delivery demand charges; Class A customers under the Industrial Conservation Initiative pay a share of provincial GA based on their demand during Ontario's five annual system peak hours, which makes peaks disproportionately expensive. Quebec's Hydro-Québec Rate M applies a per-kilowatt billing demand with a minimum tied to the highest demand of the preceding 12 months. BC Hydro's medium and large general service rates include a demand charge plus a minimum tied to prior months. Alberta transmission and distribution charges for larger sites are also demand-based. In every case, energy rates are in cents per kWh while demand rates are in dollars per kW — the demand line is where a short surge does real damage.

This is the part that surprises people. Many Canadian commercial tariffs set your billing demand as the higher of (a) this month's measured peak and (b) a percentage — often 65% to 90% — of the highest peak recorded in the previous 11 or 12 months. Hydro-Québec's Rate M and several BC Hydro and utility-specific large general service rates use this structure. The practical consequence: a single unplanned simultaneous start-up in February can raise your floor demand through the following January. Read your tariff for the exact ratchet percentage and look-back window; those two numbers determine how long a mistake costs you.

Ask your utility or your retailer for your interval data — most Canadian utilities provide 15-minute or hourly consumption data through a customer portal (Hydro-Québec, BC Hydro, Hydro Ottawa, Toronto Hydro and others offer downloadable interval files). Then do three things. First, plot the month and find the single highest interval — that is your billing demand. Second, compare it to the demand kW printed on your invoice; if the invoice number is higher than this month's measured peak, a ratchet from an earlier month is already active. Third, look at what was running during that interval: in most sites the culprit is coincidence, not capacity — a compressor, a chiller, a charger and a production line all starting inside the same quarter hour.

Sequencing and interlocks come first and usually cost nothing but engineering time: stagger motor starts, prevent two large loads from starting in the same interval, and add soft starters or VFDs where inrush is the problem. Next is load shedding on a real-time signal — a controller that watches the running 15-minute average and drops non-critical loads (space heating, some ventilation, non-urgent charging) before the interval closes. EV fleet charging in Canada is a common new peak driver and is highly schedulable; shifting it out of the plant's peak window is often the single biggest win. Battery storage is the last resort and the most capital-intensive: it discharges through the peak so the meter never sees it, and it also opens arbitrage and backup value. Size it against your measured peak profile, not against a rule of thumb.

Several Canadian jurisdictions actively pay for peak reduction rather than only charging for peaks. Ontario's Industrial Conservation Initiative lets qualifying Class A customers reduce their Global Adjustment cost by curtailing during system peak hours. The Independent Electricity System Operator runs demand response procurement in Ontario. Save on Energy in Ontario, Efficiency Manitoba, Hydro-Québec's efficiency programs for business customers, and BC Hydro's industrial and commercial energy management offerings have supported metering, controls and efficiency measures. The federal Canada Greener Homes and various clean-technology investment tax credits target different segments. Program names, budgets and eligibility change frequently — confirm current terms directly with the utility or program administrator before building a business case on them.