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Calculator · E-502

Service capacity & headroom calculator

How much of an existing service a building already uses, from its recorded peak demand, and whether the loads you plan to add fit.

Service capacity & headroom · E-502Metric · SI
A
kW
From the demand line on the utility bill: the highest in the last 12 months.
PF
If the bill reports kVA, set PF to 1 and enter the kVA as the peak.
kVA
—

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Planning estimate only. The code-compliant load calculation for a permit is done by a qualified person.

CCT 01How it works

The service’s capacity is its rating in kVA: √3 × V × A ÷ 1,000 for three phase. The building’s peak apparent power is the recorded peak kW divided by the power factor. Headroom is capacity minus the peak minus what you plan to add, shown in kVA and in amps at the service voltage.

ENMAX Power meters larger services through current transformers1 and records demand, so most commercial accounts already have the peak on the bill. See CT metering explained.

CCT 02Assumptions and limits

  • The Canadian Electrical Code has its own rules on when recorded demand may be used for a load calculation and how new load is added (Section 8). A contractor or engineer applies them for the permit; this calculator shows the arithmetic, not the code result.
  • Twelve months of data catch winter heating and summer cooling peaks; a shorter record can understate the peak.
  • Whether ENMAX can supply more capacity at the address is a separate question, answered through a service application. See ENMAX commercial service connections.

Questions people ask

How do I know if my building needs a service upgrade?

Start with the peak demand on the bill and the main breaker rating, then add the loads you plan: EV chargers, heat pumps, kitchen equipment, a new tenant. If the result approaches the service rating, a load study and a conversation with ENMAX come next. Read commercial service upgrades.

Where do I find peak demand?

On a demand-metered account it is printed on the bill, in kW or kVA, for the billing period. Ask the retailer or ENMAX for twelve months of interval data if you need the pattern, not just the peak.

Can load management avoid an upgrade?

Often, for EV charging: an energy management system shares the headroom between chargers instead of reserving full power for each. See the EV parkade capacity calculator.

Sources

  1. Get the power flowingENMAX Power Corporation · retrieved 2026-09-25