From the article: "Full-spectrum LEDs seem to output about 75 lumens per watt, so if our panel is 20k lumens then we should expect our panel to draw 266 watts.

From the article: "Full-spectrum LEDs seem to output about 75 lumens per watt, so if our panel is 20k lumens then we should expect our panel to draw 266 watts. This seems reasonable to me. If you leave it on 8 hours a day, you’re going to use 25 cents per day in electricity (at $.12 per kWh)." Almost anything can be solar powered.