even though the photo period would be reduced, all the white snow outside will reflect a lot of extra light. In Minnesota you can get sunburned in winter due to the light bouncing off the snow. and as far as supplemental lighting you can get compact daylight spectrum flourescent bulb that puts out an equivalent of a 100W bulb. It only takes 23 watts though. Maybe a few in some desk lamps would help. that will be my set up, although i only have 1 nep.