Greenhouse lights

I intend to grow lettuce during the winter in my greenhouse. Are the full spectrum plant lights expensive? Would ordinary shop lights with 40 watt tubes work just as well?

Hello Lettuceman....try your idea in a small section. I intend to do the same. I know people who grow pot in their closet using [a] 40wt bulb and it seems to work okay for that purpose.
My idea is using a 60wt would give more radient heat, which seems to be suitable for my purpose. I also will need to check the temp on a morning, evening and night time basis. I will have to record any differences and adjust bulb wts accordingly.
Hopefully I have helped you.

Lettuceman, you don't need the full spectrum grow lamps.

Cool-white fluorescents, in the blue spectrum, should work just fine for lettuce. If you are growing flowering plants, you can combine one cool white with one warm white tube in the same fixture.

Fluorescent fixtures need to be very close to seedlings to be effective. Keep you lamp 2-3" away from the plants.

SB