Just got this at work, not heard of it before now -

The UK's first Energy Saving Day (E-Day) will
happen between 6pm on Wednesday 27 February
and 6pm on Thursday 28 February. The day will
highlight the potential for energy saving measures in
the course of a typical 24 hours and will be trying to
show how even small energy saving measures can
be made to add up, and potentially play a part in
tackling climate change.
During this experiment everyone in the country will be
invited to see if they can save energy in their home,
school or office, by leaving off electrical items such as
lights in rooms that are not being used, televisions left
on standby, mobile phone chargers left plugged in.
The National Grid will assess what difference the day makes to
national energy consumption and the cumulative effects of
millions of energy saving measures will be updated on the EDay
website, on a minute-by-minute basis.
From 6pm on Wednesday 27th February please remember to switch off all
unused items at home and at work, and to check the E-Day website to see how
well the country is doing.