Rate option structure

The price applicable to additional electricity, which covers both power and energy, varies month to month and reflects Hydro‑Québecʼs marginal supply cost. It cannot be lower than 4.988¢ per kilowatthour.

On the basis of load management requirements and system availability, Hydro‑Québec reserves the right to prohibit, on two hours’ notice, consumption of additional electricity.

Calculation of billing amount

Energy billed as additional electricity is calculated in 15-minute blocks.

  • Consumption that exceeds the reference power is billed at the applicable price for additional electricity.
  • The reference power and the rest of the energy are billed at Rate L or LG prices and conditions.

Conditions of application

Hydro‑Québec will inform you of the price of additional electricity seven business days prior to the start of each calendar month. The price remains the same for the full month.

To take advantage of this option, you must apply to Hydro‑Québec at least five business days prior to the start of the consumption period.

The option goes into effect at the beginning of the consumption period, subject to an agreement on reference power and Hydro‑Québecʼs acceptance.

You must agree to adhere to the Additional Electricity Option for a whole consumption period.

More information

If you have any questions about this rate option, contact your commercial officer or designated agent. You can also reach our Business customer services by phone at 1 800 463‑9900 or by email at business@hydro.qc.ca.

This information has been simplified. For more details about the Additional Electricity Option for medium power customers, consult Section 3 of Chapter 6 of the Electricity Rates [PDF 4.75 MB].


Total amount of electricity supplied at a given time. Expressed in kilowatts (kW), power is the combined effect of voltage, expressed in kilovolts (kV), and current, expressed in amperes (A).


Power used by electrical equipment over a given period of time. Expressed in kilowatthours (kWh), energy is calculated as power, expressed in kilowatts (kW), multiplied by the time during which the power is used, expressed in hours (h).

The formula for energy is as follows: energy (in kilowatthours) is equal to power (in kilowatts) multiplied by duration of use (in hours).

Minimum for the price of additional electricity

The price of additional electricity cannot be lower than the average price at Rate L, expressed in ¢/kWh, for 120 kV service and a 100% load factor.

  • Billing of the reference power and corresponding energy consumption is based on the prices and conditions for the applicable Rate L or LG.
  • All excess consumption is billed at the applicable rate for additional electricity.

Reference power

Reference power must reflect the customer’s normal consumption at Rate L or LG. It is expressed in kilowatts (kW).

Consumption period

Period during which electricity is delivered to the customer and which extends between the two dates used by Hydro-Québec for calculation of the bill.