It's something we take largely for granted - until it goes off. But maintaining our electricity supply is a busy job.
Engineers from Northern Powergrid spend much of the summer checking cables, poles and pylons for any problems that could cause power cuts in the winter. But with much of the infrastructure criss-crossing country fields, there's only one effective way to do it.
Between July and October, two helicopter flights per day, five days per week fly over power lines stretching 10,000 miles. Engineers inspect up to 100,000 poles, and send ground teams to about 1,000 potential problems.
They say without these flights, we'd all have to suffer many more power cuts.