- I have 8 white widows growing in a closet 4 ft by 2 ft. - There is currently a single 400W switchable lamp in there. I am going to buy another Switchable lamp. Should I A) use a single lamp with 1ooo watts B) use a 400 Watt and a 100o watt lamp. (is 1400 watts per hour additional to regular electric usage suspicious?) C) use 2 400 watt lamps Anything else you guys suggest WILL be taken into consideration.