Uselessly filling storage devices incurs a needless and wasteful environmental cost, just the same as computing hashes does. At least Filecoin provides distributed storage, which allows the storage devices to be put to something resembling their intended use.
From what I read about Chia, the marketing is the exact opposite : most people have unused storage space, and they will never use it (phones and computers). The Chia network proposes to make that free space more "useful".
Filecoin enforces tremendous waste, only a small portion of total network space is used for storage. The equipment needed to mine costs tens of thousands of dollars.
With Chia, anyone can farm with minimal electricity cost (after plotting).
it increases security per unit of energy significantly making the amount of energy needed to secure the network orders of magnitude smaller than bitcoin. its also asic resistant, and having a lower barrier to entry makes it so the people with 0 cost basis just filling up extra space on their drive will outcompete & push out any large data farms increasing decentralization as well.
Your point about electricity cost is true. Once plotting is done (which takes hours per plot, few days for most drives), the only power draw is on idle drives. The transactions don’t require endless plotting the way proof of work would require endless mining.
Storj recommends you have a server with at least 128GB of ram and a powerful GPU before joining the network. The problem is the whole system is zero trust so you must constantly be calculating proofs to show you have all of the data and that it is always available.
It’s much more efficient to just have one large data enter with a reputation and trust. They have to store all of the data to keep their reputation.
