Ads cost energy -- the electrical kind -- to make. But CHI & Partners, quite creatively, has used client Direct Energy's 'Free Power Day' scheme to produce all of its advertising for no money at all.

Direct Energy customers get a free power day, where they can choose a day of the week to get all their electricity for free -- and do their big energy-using tasks like vacuuming, laundry and cooking on those days.

So the agency recorded its radio advertising (the videos seen here are the behind the scenes look at the work) inside a customer's home on free power day.

Check out all the executions on the right.