Calculating Energy Cost

When a run is complete, we are interested in several data points:

• The SYSmark* 2004 SE overall score

• Completion time of the test run

• Average system power draw during the Internet Content Creation test run

• Average system power draw during the Office Productivity test run

• Idle system power draw

• Standby system power draw

For example, Intel has measured the following performance and energy cost for the Intel® Core™ 2 Duo E4300 processor with integrated graphics on the Intel® Express Intel® DG965SS motherboard. For full system configuration details, please see final page of this document. Note that both Enhanced Intel® SpeedStep™ Technology and Minimal Power Management are enabled.

Energy Cost per KWh $0.07765

Avg. System Power Idle (watts) 49.892

Avg System Power Standby (watts) 2.898

Avg. System Power OP (watts) 56.934

Avg. System Power ICC (watts) 62.821

Time to Complete - OP (minutes) 51.4

Time to Complete - ICC (minutes) 45.25

Time to Complete - Total (minutes) 96.64

Idle Time After Run (minutes) 15

Standby Time After Run (minutes) 8.36

Performance tests and ratings are measured using specific computer systems and/or components. Actual results may vary.

Note that the kilowatt-hour figures will be small decimal numbers and will be eventually multiplied by much larger numbers. As such, it is important to avoid rounding off until after the final energy cost calculation has been made.

For this example, we are using an energy cost of $0.10/Kilowatt-Hour (KWh). This figure will vary by country, and a localized energy cost value can easily be substituted.

So, to calculate a daily energy cost, we first need to understand how much energy is consumed during the course of a single SYSmark* 2004 SE run.

We first take the average power during the Office Productivity (OP) and Internet Content Creation (ICC) runs:

OP avg. power draw x completion time

56.934W x 51.4 minutes = 2926.408 watt-minutes

Then convert to watt-hours:

2926.408 watt-minutes / 60,000 = 0.048773 KWh

ICC avg. power draw x completion time

62.821W x 45.25 minutes = 2842.65 watt-minutes

Then convert to kilowatt-hours:

2842.65 watt-minutes / 60,000 = 0.047378 KWh

Now calculate energy use during single two-hour window:

OP energy + ICC energy = total SYSmark*

0.048773 + 0. 047378 = 0.096151 KWh

Then comes 15 minutes of the system at idle:

49.9W x 15 minutes = 748.5 watt-minutes

Then convert to kilowatt-hours:

748.5 watt-minutes / 60,000 = 0.012473

Now the system goes to sleep for the remainder of the two-hour work window.

18.35 minutes of Standby x 2.898 W = 24.215 watt-minutes

Then convert to kilowatt-hours:

24.215 watt-minutes / 60,000 = 0.000404 KWh

Next, calculate energy use during the entire workday:

Four Two-Hour Windows

(0.096151 + .012473 + 0.000404) * 4 = 0.436110 KWh

Lunch

60 minutes of standby x 2.898W = 174 watt-min

174 watt-minutes / 60,000 = 0.0029 KWh

After-Hours

900 minutes of Standby x 2.898 W = 2610 watt-minutes

3060 watt-minutes / 60,000 = 0.0435 KWh

Adding the three figures, we get:

0.436110 KWh (four two-hour windows)

0.0029 KWh (lunch)

0.0435 KWh (after-hours Standby)

0.48251 KWh over 24 hours

Getting down to dollars and cents, here’s what we see:

Workday Daily Energy Cost:

0.48251 KWh x $0.07765/KWh = $0.0374669

On non-Working days, the system is asleep, so:

2.898 W x 1440 minutes (which is 24 hours) = 4,176 watt-minutes

Then convert to kilowatt-hours:

4,176 watt-minutes / 60,000 = 0.0696KWh

Converting to dollars:

0.0696KWh x $0.07765/KWh = $0.005405

Yearly Energy Cost (assumes 240 workdays + 125 non-workdays where system is at standby)

($0.0374669 x 240) + ($0.005405 x 125)