If you are already using electric space heaters to supplement specific rooms it's a roughly 1:1 exchange but with the added benefit of mining a bitcoin subsidy.

Depending how you do it. You could save electricity overall by lowering your whole-house thermostat and simply plugging the s9 into the specific rooms you want additional heat (like am office during the day and a bedroom at night). Cheaper overall than heating your entire home and rooms you aren't using all day and night.