Instead of buying an electric heater, I'd like to buy a server that automatically sells its power on a market like this to subsidise my electricity bill.
If all electric heaters in the world provided CPU power for us as well, where would we be?
The CPU time on a server located in a data center is worth money, but CPU time on a server in your house is worthless due to bandwidth and other issues.
That's not true. It depends on the kind of workload, which can be CPU-bound, IO-bound, network-bound, etc...
If a workload is truly distributed, simply fetches data blocks to process then goes computing for a while (Example: folding@home), the amount of bandwidth doesn't matter.
Also, some people have substantial amounts of bandwidth to their house :)
If all electric heaters in the world provided CPU power for us as well, where would we be?