These outdoor heaters can be used indoors as well. The heaters have a G4 stainless steel shell that never rusts. This particular unit heats an area up to 4m x 4m and has a quartz dual element that converts 90% of the electricity supplied into heat. The unique technology means that the heaters heat only solid objects and not the air inbetween. Also this unit is not affected by wind. Delivered free to any UK mainland location within 3-4 working days from order.