The proof-of-waste system means that, at market equilibrium, the cost of burning electricity to mine one block and get the 25 bitcoin reward should be equal to the cost of buying it on the open market.<p>Currently this works out as about $7 of electricity per transaction. <a href="https:&#x2F;&#x2F;blockchain.info&#x2F;charts&#x2F;cost-per-transaction" rel="nofollow">https:&#x2F;&#x2F;blockchain.info&#x2F;charts&#x2F;cost-per-transaction</a>