mini project

Low watt = turn down the power. 😹💚 I think you are about high efficiency. That's a difficult topic depending on LED driver, LED type and so on. Two steps without much knowledge: Make sure that your LED has efficient LEDs. ~2 years ago I guess Samsung LM301H had the highest efficiency (don't know if there is anything new - EVO has a lower efficiency if I remember right). Count the LEDs - Higher number - Higher efficiency. I think without testing this is all you can do. Nonetheless, DIY can be built more efficiently than anything on the market, as you can just take the most efficient LEDs in a higher number than anything available. This would mean a rather pricey lamp, but with less heat and such, its longevity is improved, too. Everything in theory, e.g. if you solder the contacts (if you don't have plugs) badly, you lose efficiency. Anyway, if you ask for low watt LED, you probably shouldn't go for DIY, electricity is dangerous ;-) Edit: There is just so much a company can spare compared to private users. Another good hint is the price - I wouldn't buy something if it's below (!) 1€/Watt, because at some point you have to save on quality / parts.