Case Study: Installing “presence detectors” to reduce running costs of the lighting

We have a project on Installing motion sensors to cut costs to a property.

This calculation is based on the following factors:

  1. Electricity price of 10 pence per KW unit.
  2. 36 x 28watt 2D fittings
  3. 10 x 50watt low voltage fittings
  4. 3 x 60w HQI fittings (external)

If the existing internal light fittings are on 24hrs a day and the external are on an average 12hours a night the costings are the following:

36 x 28w 2D light fittings = 1008w.  1008w x 24hrs = 24192watts per day (24kw)

24kw x 365 days = 8760kw per year.

8760kw x 10pence = £876 per year

10 x 50w = 500w.  500w x 24hrs = 12000watts per day (12kw)

12kw x 365 days = 4380kw per year

4380kw x 10pence = £438 per year

3 x 60w = 180w. 180w x 12hrs (dusk to dawn sensors) = 2160watts per night (2.1kw)

2.1 x 365 nights = 766kw per year

766kw x 10 pence = £76 per year

This equates to about 47,000 kg’s of CO2 per year.

If motion sensors are to be installed where required, then the average time the lights are on is about 4 hours a day.

36 x 28w = 1008w.  1008w x 4hrs = 4032watts per day (4kw)

4kw x 365 days = 1460kw per year.

1460kw x 10pence = £146 per year

10 x 50w = 500w.  500w x 4hrs = 2000watts per day (2kw)

2kw x 365 days = 730kw per year

730kw x 10pence = £73 per year


The external lights would stay as they are.

Projected savings of about £1000 per annum

This would produce about 8000 kg’s of CO2 per year. Saving a massive 39,000 kg,s of CO2.

For more info Please contact our Contracting Team on 020 7486 9075 or Email :


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