a 400w light on 18 hrs a day will cost you about £2 a week.
how high are you planning on building your box, my guess is that it will have to be at least 6ft tall. to allow for growth of plants and the distance from the top of your plant to the light.
i cut a piece of plyboard to exactly fit into my window frame, i closed the curtains and squeeze the board in and no light escapes. it just looks like your cutains are drawn all the time.
jolly green giant Reviewed by jolly green giant on . Rookie Grower 1. How much more on your energy bill for a 400 watt Sodium light? 2. If I were to create a 4x4 box in a room, would I really want to line it with tin foil on the inside? Is that 400 watt light enough for 6-8 plants? I worry about the neighbors seeing these lights on, thats why I wouldnt want to make the whole room a grow room. Any suggestions to get me going. Rating: 5