Yes, and the plants make it easy. A leaf counts photons and cannot tell whether they came from the sun or from a diode, so plants under grow lights only build sugar the same way an outdoor plant does. The number that decides everything is how many photons land on the leaves each day. Hit that target and a window stops mattering.
A windowless basement shelf grows crisp lettuce all winter. A bright kitchen window often never ripens a single tomato. That looks backward until you count photons instead of hours of brightness. The shelf delivers the same dose every day of the year, while the window swings with the weather and the season. Sole source lighting wins on consistency before it wins on anything else.
The measurement behind all of this is the daily light integral, the running total of photons a plant collects between lights on and lights off. Iowa State University Extension puts low light foliage houseplants at 3 to 6 mol/m²/day and fruiting herbs and vegetables at 18 to 30. Five to six times the light for the same patch of shelf. That gap is why a pothos does well under a cheap strip light while a pepper plant sulks under the exact same fixture.
Two dials get you to the same daily total. Brightness at the leaf and the hours you run the fixture multiply together, so a modest light running 14 hours can deliver more than a bright one running four. That is why the basement shelf keeps up with the window. The window may win at noon, but it quits early, and it quits much harder in winter.
The same math sorts houseplants into tiers. Ordinary foliage plants sit near 4 to 6 mol/m²/day, shade plants near 6 to 8, part shade types around 10 to 12, and full sun plants want 14 to 20. A fern on a dim shelf needs a fraction of what a rosemary plant needs. One fixture that keeps the fern glossy will leave the rosemary thin and stretched.
Crop numbers make the split obvious. Lettuce wants 12 to 17 mol/m²/day, basil 15 to 25, and a tomato 20 to 30. Leaves are cheap for a plant to build, so leafy crops move indoors without much fuss. Fruit is expensive. A tomato has to fund flowers first and then pour sugar into every fruit, which is why it asks for close to double what a salad crop asks for.
So the practical answer splits by crop. Herbs, salad greens and most foliage houseplants do fine on electric light alone, and plenty of growers have run them that way for years. Fruiting crops work too, but you pay for every photon you deliver. One commercial comparison put the payback for sole source LEDs against high pressure sodium at 3 to 5 years. Nobody has published that math for a shelf at home.
Do not fix a low daily total by leaving the lights on around the clock. Keep the total at 16 hours a day or less, because most plants need a dark period. Treat that ceiling as fixed, then find the rest of your photons somewhere else.
You have four levers for raising the daily total. Put in a different fixture, add more fixtures, move the light closer to the canopy, or stretch the run hours up to that 16 hour cap. Most people reach for hours first because it costs nothing, and then they run out of room. Moving the fixture closer is often the cheaper win. Growing plants without sunlight is mostly arithmetic. Pick the target for your crop and measure what actually reaches leaf height. One of those four levers closes the gap.
Read the full article: Grow Lights for Indoor Plants: What Really Works
