A 35W draw will cost you $5/mo at $0.20/kWh. This will either let you run an oldish laptop continuously, or you can go down the path of newer hardware to optimize your constant draw, and spend that energy budget on in-use amenities (nice monitor or faster processing).
But looking at the bigger picture, why would you want to set a limit on your computing costs so low? Today's dominant business model is to use scaled computational processes to trick people into overpaying for products/services. One of the least prudent things an individual could do is further hinder their ability to exercise their own computational agency!