Like many other mining enthusiasts no doubt, I have migrated from S1's to S3's and now have S1's gathering dust. So what to do with them? They are undervolted and lowered frequency using 150watts at 128Gh. Running costs are £0.50p per day each. They run almost silent. l intend using one per bedroom to warm the room up and maybe point them at a solo pool.. you never know your luck or l could stay with my usual pool and then the running costs drop to £0.10p per day.
As an aside I have 6 S3's all providing heating. It's winter here in England with outside temperatures ranging from 0 to 10C. One S3 is in the shed to keep the place from freezing, 3 in the lounge hidden in a corner.. the temperature there now never drops below 22C.. and 2 in my study which keeps it comfortably warm. Fan noise is not a problem having replaced all fans with much quieter ones.
I too have undervoltaged S1s (8 of them) and S3s (5). They're all in my basement and help heat the whole house. We live in Ohio and have a quad-level home. Current outside temperature about 36 F, keeps basement at about 78 F; 2nd level at 72 F; third level about 69 F; and 4th level at about 65 F. The bedroom we sleep in is upstairs and prefer the cool temp so works out great. Making about 1.5 BTC a month. I check the electric bill each month and compare to the BTC made during same period and will continue running as long as still making money. Furnace hardly runs at all so also saving on natural gas bill. Noise not a problem because of location.