It'd be all new wire run (120 is split at the panel, we aren't running 240v all over the house) and currently electricians are at a premium so it'd likely end up costing a thousand+ to run that if you're using an electrician, more if there's not clear access from an attic/basement/crawlspace.
Though I think it's unlikely we'll see an actual need for it at home, I imaging a 800w cpu is going to be for server class CPUs and rare-ish to see in home environments.