Full Spectrum Light Bulbs
In the fall and winter you have to use supplemental lighting for your growing to increase the length of light even in bright areas of the country. You have to convince the grass that it is Spring so that it keeps on growing. If it knows that it is Winter then the growth will slow down and you won't get your regular dose of juice.
You have to give the sprouter light for 14 hours total. That could be ten hours of normal light plus 4 hours of extra lights or any combination that works in your climate.
Some people have asked if keeping the lights on all the time is a good idea. Nope, all living things need a rest period when different work is accomplished in the dark.
You can also grow your wheatgrass year round in the basement by using full spectrum lights. The light I recommend is a flourescent fixture disguised as an incandescent. Meaning that you can screw it into any fixture you already have that takes screw-in lightbulbs. It uses 75% less energy than regular incandescents, which are totally outdated and environmentally unsound. If you replace all the incandescent bulbs in your house you would be doing a service to the environment.
I was selling a good version of these lights but the company went out of business and when I researched I found that you can get pretty good ones much cheaper now at Home Depot and other places. You don't need any of the fancy lights sold for growing flowers because the wheatgrass never comes to bloom.
Someone asked which bulb specifically so I found one at Home Depot made by N:Vision. It is daylight - 5600 Kelvin. The 27 watt bulb is equivalent to 100w incandescent and it was under ten dollars. If you can't find this one then any that are over 5000 Kelvin would do. Soft white will not do, it doesn't have the full spectrum of light that plants need.
Many people will only need one of these bulbs to grow their grass. If your house is pretty dark in the winter then two would be better. If you are growing in the dark, then three would be best. I would recommend using clip-on lamps attached to furniture close to your sprouter or the cheap gooseneck floor lamps will do also. You'd want the light 1-2 feet above the sprouter and shining down at a 45 deg angle so the light goes into the top 3 trays.
If you have two lights have one on each side of the sprouter and if you just have one, then turn the trays as you water them each day.