Windows home server build that is energy efficient [migrated]

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http://serverfault.com – I want to build a home server and I plan to run windows server 2012 essentials. I want to use it for storage, file sharing, dlna to my tv, host a couple of websites (not much traffic if any at all) and maybe run a minecraft server on it (but not essential obviously). I'm concerned that having a computer running 24/7 is going to blow out my electricity bill so is there a way to minimize power usage? What sort of wattage should I expect a server to use? What hardware component uses the most power? (HowTos)