Comparing it to as a percentage to what servers use is a spurious relationship. An energy saving is an energy saving. Servers need to be on and lights don't. 20W*hundreds of racks (plus extra for heat extraction) is still greater than a couple of 5 watt headlamps - why spend money on this if you don't need to?
By some estimates, Google has the equivalent of 25000 racks of hardware, maybe at most a quarter of them hosted in the shared facilities where they turn the lights off, say 6000 racks of hardware. Continuing my calculation, that would be 3000 ~20W fluorescent light strips. If running 24/7, they would consume 530 MWh/year. This is only $53k/year at the average utility rate of $.10/kWh.
If you continue to argue that Google, a company making $30B+ of revenue/year, turned off the lights to save a meager $53k/year, you are making a fool of yourself. They would save more by merely firing this secretary who smokes cigarettes in the bathroom during lunch breaks.
Google is all about efficiency, down to giving technicians scooters to quickly move through large data centers, and choosing the optimal placement of velcros strapping hard disks to the chassis for ease of service. I bet they would rather leave the lights on rather than fumble with headlamps or flashlights...
Clearly the article is right, Google did it for privacy reasons.
You did not take into account the energy to create those headlamps, and to replace worn batteries. I estimate each headlamp uses as much energy as a 15 watt lamp burning continuously for a year.
Depending on how much they use them (they probably last around 500 hours before being worn out) they may come out ahead or behind, but it's not a slam dunk.
> plus extra for heat extraction
To extract the heat takes 1/3 as much energy as was emitted, if that helps your calculations.
I also didn't include the energy (or cost) to create thousands of fluoro tubes, nor the human wages paid to constantly replace the ones that go... which is going to be far more than a couple of headlamps you can buy from the $1 store and some rechargable batteries.
> Depending on how much they use them (they probably last around 500 hours before being worn out) they may come out ahead or behind, but it's not a slam dunk.
I agree that 'how much you use them' is important. None of us really know how often they are accessed, but to me even for a very heavily accessed facility it does feel like a 'slam dunk'. If you feel the opposite maybe we just disagree here.
I'm not sure what wears out after 500 hours by the way: Batteries? LED lighting? Neither are going to cost an arm and a leg.
