The fallacy that it doesn’t cost much to leave equipment running

• Off-peak electricity rates are from 11pm to 7am and all day on weekends
• The period 6 pm to 11 pm is still at peak rates
• Assuming peak electricity costs $0.12 and off peak $0.04, a 100 watt load left on 24/7 year round will use around $31 worth of electricity a year during the 50 hours a week the office is occupied, and $37 when its unoccupied
• There is no peak/off-peak distinction when it comes to greenhouse pollution – electricity generation doesn’t magically become any cleaner during off-peak hours. A 100 watt load will produce 860 kgs of greenhouse pollution when the office is unoccupied, compared with 360 kgs during occupied times.

Leaving equipment on

• costs money
• causes unnecessary greenhouse pollution
• can reduce equipment life and add to maintenance costs.

What is a reasonable percentage of out of hours use?

• This depends on cleaners' schedules, if there are staff who work back very late or start very early and if the site has a server room.
• Aim for a target of 20% to 30% if there is no server room.
• This means that off-peak use will be around 15% to 22% of your total electricity usage, or roughly one-fifth to one-quarter of your peak use.

Check your electricity bills for the percentage of off-peak use and aim to make it one-fifth of your peak use.