This option applies to a Rate M or G9 contract whose maximum power demand has been at least 500 kilowatts (kW) during a consumption period included in the 12 consecutive monthly periods preceding the date of the sign-up request.

Rate option structure

The price applicable to additional electricity, which covers both power and energy, varies month to month and is based on Hydro‑Québec’s marginal supply costs. It cannot be lower than * per kilowatthour.

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

Hydro‑Québec will notify you of the price of additional electricity seven business days before the beginning of each calendar month. This price will remain fixed for the entire monthly period.

* Rate in effect as of April 1, . This information does not replace the Electricity Rates document in any way whatsoever.

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 corresponding energy are billed at the prices and conditions in effect for Rate M or G9.

How to sign up for this rate option

You must submit your initial written request to Hydro Québec at least 15 business days before the start of the consumption period for which you would like to avail yourself of the option.

Subject to installation of the appropriate metering equipment, agreement on the reference power and Hydro‑Québec’s written approval, the option takes effect at the beginning of the consumption period following the period during which Hydro‑Québec receives your written request.

Thereafter, you must submit a written request to Hydro‑Québec at least five business days before the start of the consumption period to which you would like the option to apply.

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

This information has been simplified. For more details about the Additional Electricity Option for medium-power customers, consult Section 7 of Chapter 4 of the Electricity Rates [PDF 1.44 MB].

Maximum power demand

Maximum power measured during a consumption period. It is the higher of the following two values: real power in kilowatts (kW), or a percentage (90% for domestic rates and small- and medium-power rates, or 95% for large‑power rates) of the apparent power in kilovoltamperes (kVA).

Monthly periods

Period of 30 days, which may begin on any day of the month, established by Hydro‑Québec for billing purposes.


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 price of additional electricity

The price of additional electricity cannot be lower than an average price, expressed in cents per kilowatthour.

  • The reference power and corresponding energy consumption are billed at the prices and conditions in effect for Rate D, DP, DM, G, M, G9, or LG.
  • All excess consumption is billed at the applicable rate for additional electricity.

Reference power

The reference power reflects the customer’s normal consumption profile at Rate D, DP, DM, G, M, G9 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.