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Division (e) Calculation methods

United Kingdom

Original text. Later amendments are not shown.

The TEC value reflects assumptions about how many hours a day the product is in general use, the pattern of use during those hours, and the default delay times that the product uses to transition to lower power modes. All electricity measurements are made as accumulated energy over time, and then converted to power by dividing by the length of the time period.

The calculations are based on imaging jobs comprising two clusters each day with the unit going into its lowest power mode in between (as during a lunch break), as illustrated in Figure 2 further below. It is assumed that weekends have no usage, and no manual switching-off is done.

Final time is the period of time from the last job being initiated to the start of the lowest power mode (Auto-off for copiers, digital duplicators and MFDs without print capability; and sleep for printers, digital duplicators and MFDs with print capability, and fax machines) minus the 15-minute job interval time.

The following two equations are used for all product types:

  • Average job energy = (Job2 + Job3 + Job4)/3

  • Daily job energy = (Job1 × 2) + [(Jobs per day — 2) × Average job energy)]

The calculation method for printers, digital duplicators and MFDs with print capability, and fax machines also uses the following three equations:

  • Daily sleep energy = [24 hours — ((Jobs per day/4) + (Final time × 2))] × Sleep power

  • Daily energy = Daily job energy + (2 × Final energy) + Daily sleep energy

  • TEC = (Daily energy × 5) + (Sleep power × 48)

The calculation method for copiers, digital duplicators and MFDs without print capability also uses the following three equations:

  • Daily auto-off energy = [24 hours — ((Jobs per day/4) + (Final time × 2))] × Auto-off power

  • Daily energy = Daily job energy + (2 × Final energy) + Daily auto-off energy

  • TEC = (Daily energy × 5) + (Auto-off power × 48)

The specifications of the metering equipment and ranges used in each measurement must be reported. Measurements must be conducted so as to result in a total potential error in the TEC value of no more than 5 %. Accuracy does not need to be reported for cases where the potential error is below 5 %. When the potential measurement error is close to 5 %, manufacturers should take measures to confirm that it complies with the 5 % limit.