When the last person out at night turns off the lights how many of us are lulled into a false sense of security into thinking that the energy consumption of our offices or factory also switches off for the night?
We always fit energy loggers to record out-of-hours electricity consumption as part of the energy review carried out to implement the ISO 50001 Energy Management System.
The results, as might be imagined, are very mixed but on several occasions the logging equipment revealed some alarming instances where the non-working hours demands when the building(s) are unoccupied were not massively different from the working hours demands.
The chart that follows illustrates an example of one of our energy loggers monitoring the air conditioning consumption on just one floor of a six-storey office building in North London.
The blue rectangle highlights the electricity consumption between 7:00pm and 6:00am and reveals that nearly 300 kWh were consumed by the air conditioning system for maintaining a set point temperature of 19.0 degrees Celsius in the offices despite the building being unoccupied.
By extrapolating the kWh result by the number of non-working hours per year the estimated wasted energy amounted to a staggering £16,640 per year and that was on just one floor of the six-storey building.
Further investigation of the air conditioning system revealed that the timer function on the local controllers appeared to have not been properly setup since the split units were installed several years previous.
Occupancy sensors that may be purchased as an optional extra from the suppliers or even retrofitted also switch off the air conditioning when no people are present and thus help to make a further dent in energy bills.
The findings of the energy review supported our previous observations made under ESOS whereby significant improvement in energy performance can often be achieved with little or sometimes no capital outlay.