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An ECOP User Story

Odd Monitor Power-Save Behavior

I'd like to point out something that ECOP showed us about the beta test site. The background for this case is that we're monitoring the circuit that feeds the office, which has a dual-monitor computer, a back-up power supply, and a small Ethernet switch, all of which are nearly always powered up, and a CFL ceiling light which is almost never on. Figure 1 is a reduced-size image of the actual graph, but you can still see the transitions clearly.

Figure 1: Office for the week of Jan. 24, 2010

Notice that for Sunday the usage is flat, but for the first half of Monday there is a shallow dip for nearly 12 hours. Wondering why this happened on Monday but not on Sunday, we started to theorize. We thought that maybe, under some circumstances, the computer monitors in the office were not entering power-save mode. Some trial-and-error testing confirmed this to be the case. A further bit of testing also verified that when the monitors are off a matching drop in the load can be seen in real-time using ECOP (Figure 2). We are now absolutely certain this is related to the monitors and the screen shot below shows the measurements we used to prove it.

Figure 2: Annotated screenshot of ECOP (real time) showing drop in usage on Office circuit (orange).

So, now that we know we're dealing with the monitors, we can see that on Sunday they never entered power-save mode. Sometime after 1 am on Monday they did, which we see as the drop in the graph line just after the first vertical green line in the weekly report. We verified that this is when the user stopped using them that day, and also that he started using them again a bit before noon that same day. We see this when the graph line pops back up to the higher level at that time, in between the first and second green lines. Incidentally, you can see a large drop in usage just before noon on Tuesday and this is when the consumer completely turned off the computer (though it was still plugged in so there were likely “phantom” loads from it included in that lower level usage total).

The ECOP historical reports clearly show this usage and can help save the consumer part of a penny every hour if they can determine why this happens and change the system to let power-save mode work consistently or change their behavior and just shut the monitors off manually. That may not seem like much, so let's crunch some numbers and put it into relatable terms. We'll round the lower measurement to .29 kW and the upper one to .36 kW. The difference comes to roughly .07 kW (70 watts).

Now if the consumer pays 10 cents per kWh, that comes to .7 cents per hour that can be saved by removing this particular load when it is not needed (shutting the monitors down). As an exercise, let's assume that this load should be dormant for 15 hours per day. If it never goes dormant the load costs 10.5 cents per day more than it would if it did go dormant. That's $3.15 for a 30-day month. Discover and solve just a few cases like this and you save significant costs on power, and without lowering your standard of living at all. You might save enough to go out to eat one more time each month, thereby (arguably) raising your standard of living.

To recap:

.36 kW - .29 kW = .07 kW saved when monitors are off

$.1 per kWh * .07 kW = $.007 per hour cost savings

15 hours of downtime per day * $.007 = $.105 per day cost savings

$.105 per day * 30 days = $3.15 cost savings for a 30 day month

This is obviously a simplified representation of energy billing, so the actual savings are likely much harder to determine. It is, however, a perfect real-world example that supports the studies which show that monitoring usage will reduce it because informed people can and do adapt to reduce usage, while ignorant (meaning not informed) people simply cannot reliably adapt. They have no feedback to guide them. Being more efficient is easy if you have the tools that provide that feedback.