I grow lettuce and spinach in 2ft by 4ft shelf gardens in the storage room in my basement. I use my version of the Kratke method of hydroponics. It is very cheap and easy to do. From the time I plant the seeds to when I can start picking loose leaf ButterCrunch and Merlot lettuce is 30 days. My electrical costs per year in 2023 was $5.15. I have not been able to find an in-door hydroponic system, commercial or DIY that operates this efficiently.