I would combine both. have the start-up setting in the BIOS running so start it. have a shutdown script on a schedule for every day at 7PM. but then beyond that, have a physical power timer there set to as close to 7:00 AM as you can. then have it shut off about 7:15 PM. this way you have clean start and clean shutdown but you also cut any other power draw during the 12 hours downtime.
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