I've just connected up a new UPS, and this one has an LCD screen that tells me what it's doing. Apparently, under the minimal loading that my "24/7" nettop provides (which the UPS tells me is 73W including USB disks, router, wireless AP and satellite modem etc.) the UPS is running at 93% efficiency. Which is OK, except that it occurs to me that inside the UPS is a battery charger, inverter and various switching circuits, and inside (actually outside) the nettop is a power supply that takes 240VAC and converts it to the various low voltages that the computer actually uses.
Is this the optimum way of doing this? Perhaps a 12VDC ATX power supply running directly from a battery might be more efficient? Especially in a PV-battery-inverter scenario?
Edit:
I realise this is chasing "single watt" savings and therefore not financially viable. It's just for fun!