What are you paying for electricity? So for me that makes just sense if I have excess solar energy (and of course for fun).
Discussion
It doesn't cost me all that much more than my heat pump. I believe I pay 9.7 cents per kWh.
Hmmmm..... I've been considering installing a heatpump on my RV trailer for electrical efficiency reasons, but dangit, this makes me think that I could start off with one of these for heat this winter...
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.