Here's my ghetto rig, almost 35 years old:
It started out with 6 salvaged florescent shop lights and a homemade shelf unit.
Some lights have failed and been replaced with LEDs.
For bottom heat:
Old-style Christmas tree lights, aluminum brownie pan under an overturned lattice 10x20. Depending on the heat load required, I unscrew one or two bulbs. All three will keep a full 10x20 about 75°F.
The lights are on a timer: 12 hrs for the LED, 16 for the fluorescent.
Cheap, but I have room for 12 10x20's, which supplies about everything my kids, the neighbors, and I need. When the garden was larger, I could theoretically accomodate twice as many 10x20's by switching out every 12 hours...but I never had to. By the time I was repotting tomatoes and peppers, some cabbage, etc was outside.
As the weather warms, things go outside to be parked on the southern exposure garage apron. First onions and crucifers, eventually everything.
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