how much power does your system need?

I wonder if my system is good or bad. My server needs 0.1kWh.

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You might have your units confused.

0.1kWh over how much time? Per day? Per hour? Per week?

Watthours refer to total power used to do something, from a starting point to an ending point. It makes no sense to say that a device needs a certain amount of Wh, unless you're talking about something like charging a battery to full.

Power being used by a device, (like a computer) is just watts.

Think of the difference between speed and distance. Watts is how fast power is being used, watt-hours is how much has been used, or will be used.

If you have a 500 watt PC, for example, it uses 500Wh, per hour. Or 12kWh in a day.

I forgive 'em cuz watt hours are a disgusting unit in general

idea	what	unit
speed	change in position over time	meters per second m/s
acceleration	change in speed over time	meters per second, per second m/s/s=m/s²
force	acceleration applied to each of unit of mass	kg * m/s²
work	acceleration applied along a distance, which transfers energy	kg * m/s² * m = kg * m²/s²
power	work over time	kg * m² / s³
energy expenditure	power level during units of time	(kg * m² / s³) * s = kg * m²/s²

Work over time, × time, is just work! kWh are just joules (J) with extra steps! Screw kWh, I will die on this hill!!! Raaah

Could be worse, could be BTU. And some people still use tons (of heating/cooling).
Power over time could be interpreted as power/time. Power x time isn’t power, it’s energy (=== work). But otherwise I’m with you. Joules or gtfo.
- Whoops, typo! Fixed c:

kWh is the stupidest unit ever. kWh = 1000J/s * 6060s = 3.610^6J so 0.1kWh = 360kJ
If you have a 500 watt PC, for example, it uses 500Wh, per hour. Or 12kWh in a day.
A maximum of 500 watts. Fortunately your PC doesn't actually max out your PSU or your system would crash.

130 comments