[imtringued]

If running a Bitcoin heater costs half as much as running a regular Bitcoin miner then you can spend the savings on twice as many miners to get more Bitcoin. If everyone does then the effect is net zero. However, your miner can't be a heat pump so in practice it would be net negative.

[beiller]

Yes so now 20 million people (very small amount) install these space heaters, heck install 3. Now they are at equilibrium except the mining difficulty has gone wayyy up (because 20 million ASIC miners will double the global hashrate approximately). Now mining in server racks is no longer profitable because dealing with waste heat is a major expense for them. So not only is hashing now very distributed, but also not 100% wasted.