I've replaced a wall mounted 1500w space heater with an S9. It will take a while for the BTC reward to pay off the upfront cost, but I'm super happy with the results so far, three weeks in.
To heat a good sized bathroom with cold tile floors, I run it at 600 watts, fan speed 40%. It's quiet, quieter than the really nice but in wall mounted heater. This has been producing a consistent 7-7.5 TH/s.
Obviously no massive BTC reward comes out of that, but if you're going to use electric heat to keep some rooms warm anyway, I highly recommend doing this.
Maybe it takes a few years to pay off the cost, as we only run it 6-7 months of the year and not always 24/7. But, I really enjoyed learning more about how mining rigs connect to pools etc. There's also something very satisfying about contributing a tiny bit to the Bitcoin network hash rate.
Highly recommend.
I used BTC sessions YouTube walkthrough, and the crypto cloaks PDF outline.
I did not buy the crypto cloaks fan attachments and shell though. Instead I used some pieces of plywood. I'm a cheap-ass and wanted to keep my upfront costs as low as possible just in case this didn't work out like I thought. Plus I like wood work and will be making my own case this winter.
Stay warm!