So I actually went to home depot today to try to see what I can get for now. I bought a couple 30W $20 4' led lights, which output 3000 lumen at 100 lumen/watt.
I did a test with my ppfd meter to try to aim for 200 ppfd in my 2' x 4' grow area, and it seems like I need to hang both lights around 5" from the plants. I feel like I'd need 3 lights though to evenly cover the whole area, for 90W total.
Compared to my grow lights though I'm not sure if it makes sense in the long run anymore. I used my dimmer on my grow lights to try to match the same ppfd at 5" from the plants, and I can turn it down all the way to 35W to get the same ppfd.
At 0.14$/kwh electricity cost, 15h light time per day, my projected costs are something like:
| 3 shop lights | 2 shop lights | grow light |
| Upfront cost: | 60 | 40 | 200 |
| Yearly cost | 68.985 | 45.99 | 26.8275 |
| Year | | | |
1 | 128.985 | 85.99 | 226.8275 |
2 | 197.97 | 131.98 | 253.655 |
3 | 266.955 | 177.97 | 280.4825 |
4 | 335.94 | 223.96 | 307.31 |
5 | 404.925 | 269.95 | 334.1375 |
6 | 473.91 | 315.94 | 360.965 |
With the added benefit of the grow lights having some resale value, and they're dimmable so I can turn up the brightness if the ppfd drops due to lower LED efficiency over time.
In terms of lumens, my grow lights are around 166 lumens/watt, so around 1.66x more efficient than the shop lights. I think some newer models have even higher lumen/watt.
It would really only make long term sense for me if I can somehow work with just 2 shop lights per 4 ft space. I think there were slightly higher lumen/watt shop lights at home depot too, but they were also more expensive.