They will work for seedlings but usually not for setting fruit. You need to keep them close to the plants - an inch or so max from the top leaves.

Mike

I don't believe you should have any trouble with those lights getting too hot for those shelves. Just don't mount the lights directly to the wood and you're sure to have no problems. If you do mount them to the wood, check the face they're mounted to periodically for discoloration.

But wood burns spontaneously at something like 450F or more, and those lights don't get too hot to touch so it should be fine.

You'll need more light for high-energy plants like tomatoes but if you're growing lettuce or something like that they should work fine to maturity.

Basic calculation:

Your fluorescent lights probably have somewhere between a 15% and 30% external quantum efficiency (hard to say exactly without seeing what types you bought). Probably 20%-ish. So, roughly, multiply 20% times your wattage, divide by 93W/ft^2, and divide by the number of square feet you're illuminating. The result will be the percent of how much light your plants will be getting in comparison to the full summer sun shining directly overhead on a cloudless day. So, if you bought 200W of lights and are covering three square feet, that's 200 * 20% / 93 / 3 = 11%. Then adjust that up or down based on how optimal your frequencies are for plant growing and for any re-reflection of light that you do, how good your light penetration is in comparison to the sun's, and factor in that the sun doesn't hover perfectly overhead on cloudless days 24/7. So, if reflections are doubling your light, your penetration is equivalent, your frequency spread is about as efficient as the sun's, and that clouds and the angles of the sun mean it averages only a quarter as efficient as its peak while your system always stays at peak, then your plants are getting about 88% as much energy as they'd get outside.

Which is a complicated math way of saying "yes it will grow plants but not as well as direct sunlight".

No indoor light really duplicates sunglight anyway.

Hydroponica, when you say not as well as direct sunlight, is that limited to outside? Or can that also mean 8 hours of direct sun in a heated sun room indoors?

Thanks!

Even the cleanest glass will filter a little light. However, a great deal more still comes through. You can easily get a sunburn through glass, for example, and the severity of burn you'd get compared to no glass is virtually identical.

If you can get extended direct sunlight through windows there won't be any real difference between that and without the windows, particularly when you account for the possible problems that weather, bugs, and so on can cause you.

And the difference between the average indoor growing light - even very strong ones - and sunlight is, if you'll pardon the pun, like day and night.

Some light is better than none, and more light is better than some. You want to maintain a certain minimum amount for a certain duration (depending on plant type), but with few exceptions you'll see more growth with more light.

Oh, and if you've got plants growing in windows, make sure to clean the glass - both sides - regularly. It makes a big difference. Clean glass won't block much light, but dirty glass definitely will.