A often-missed point about home mining: essentially 100% of the electricity your PC uses ends up as heat. A 400W rig in the corner of your office is, physically, a 400W space heater that happens to also hash Malairte blocks. In winter this is not waste - it is heating you would have paid for anyway.
The offset, in plain numbers
If your home is already heated with electric resistance heating (baseboards, plug-in heaters) at the same kWh rate, your mining electricity is essentially free during heating season - it does the heating job a dedicated heater would have done. If you heat with natural gas or oil, the offset is partial: your mining electricity costs more per kWh of heat than gas does, but you still avoid some heating cost.
Where to put the rig
- A small office, study, or den where you spend time benefits the most.
- An uninsulated garage or basement loses heat to the outside; the offset is weaker.
- Bedrooms work in cold months but quickly become uncomfortable in spring.
The summer flip side
From May to September the same heat becomes a problem. If you run air conditioning, your AC now has to remove the mining heat as well as the normal household heat - effectively doubling the energy cost of those mining watts. Many home miners reduce hours or shut down entirely in peak summer for this reason. See the separate guide on summer cooling considerations.
Practical tip
Treat the rig as a supplementary heater, not the primary one. A 400W rig outputs roughly 1,365 BTU/hr - enough to noticeably warm a small room, not enough to heat a house. Keep the door open so the heat circulates rather than cooking the rig itself.