Calculating Energy Cost

When a run is complete, we are interested in several data points: * The SYSmark* 2007 Preview overall score * Average system power-draw during the Video Content Creation test run * Average system power-draw during the Office Productivity test run * Average system power-draw during the E-Learning test run * Average system power-draw during the 3D Modeling test run * Completion time of the overall test run (sum of the four sub-test runs) * 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® Desktop Board DQ965GF 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.

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.

The energy cost amount will vary by country, and a localized energy cost value can easily be substituted. For this example we use 7.705 cents/KWh, which is the average of industrial and commercial energy prices in the United States as of May, 2007, according to the US Department of Energy.1

So, to calculate a daily energy cost, we first need to understand how much energy is consumed during the course of a single SYSmark* 2007 run.

We first take the average power during each of the four application segment runs:

	Average Power (watts)	Execution Time (minutes)	Energy Used (watt-minutes)
eLearning energy	71.9	11.12	799.528
video creation energy	74.2	14.83	1,100.386
office productivity energy	68.9	6.38	439.582
3D modeling energy	86.4	7.97	688.608
TOTALS		40.3	3,028.104

Then convert to kilowatt-hours, we first divide by 60, to make the units watt-hours, and then by 1,000 to make the units kilowatt-hours (KWh). So, we reduce this to a single operation by dividing by 60,000:

3,028.104 watt-minutes / 60,000 = 0.0504684 KWh

One note about SYSmark* 2007 Preview time: the EEP 2.0 model requires that each work period (morning and afternoon) contain at least three SYSmark* 2007 Preview Edition runs, and a 15-minute break. This means that a platform’s run-time on SYSmark* 2007 Preview cannot exceed 75 minutes, since three runs of that time-length plus the 15-minute break exactly equals 240 minutes, or four hours. If a system’s run-time on SYSmark* 2007 Preview does exceed 75 minutes, it is disqualified from being evaluated using this model.

Now calculate energy use during the morning period. First we determine the amount of time remaining at the end of the morning period. Recall that the first thirty minutes of this time the system will be idle, and then it goes to sleep:

Item	Time (minutes)
First SYSmark* 2007 run	40.3
Second SYSmark* 2007 run	40.3
Break	15
Third SYSmark* 2007 run	40.3
	135.9 minutes

So, we have 104.1 minutes remaining in the morning work period. The first 30 minutes of that will be at idle, so there will be 74.1 minutes of sleep during the morning work period.

Let’s next figure out the energy usage during the idle periods (15-minute break and 30-minute idle) and the sleep time of 74.1 minutes.

Total Idle time is 45 minutes, and the system idles at 59.6 watts. So:

59.6 watts x 45 minutes = 2,682 watt-minutes

Then convert to kilowatt-hours:

2,682 watt-minutes / 60,000 = 0.0447 KWh

Our example draws 3.2W of power when asleep. Now we figure out the energy consumed during the 74.1 minutes of sleep:

3.2 watts x 74.1 minutes = 237.12 watt-minutes

Then convert to kilowatt-hours:

237.12 watt-minutes / 60,000 = 0.003952 KWh

So, summing all the components of the morning work period, we have:

Item	Energy Used (KWh)
SYSmark* 2007 Run 1	0.0504684
SYSmark* 2007 Run 1	0.0504684
Break (15 minutes)	0.0149
SYSmark* 2007 Run 1	0.0504684
Idle Period (30 minutes)	0.0298
Sleep Period	0.003952
Total for Morning Session:	0.2000572

Next we calculate the energy used while the system is asleep during the lunch hour:

60 minutes x 3.2 watts = 192 watt-minutes

Then converting to kilowatt-hours:

192 watt-minutes / 60,000 = 0.0032 KWh

The afternoon work session is identical to the morning session, so the complete workday consists of:

Item	Energy Used (KWh)
Morning Session	0.2000572
Lunch	0.0032
Afternoon Session	0.2000572
Total For Workday	0.4033144

Finally, we calculate the energy used overnight while the system is sleeping. There are 15 hours between 5:00pm and 8:00am, so:

900 minutes x 3.2 watts = 2,880 watt-minutes

Converting to kilowatt-hours:

2,880 watt-minutes / 60,000 = 0.048 KWh

So the total for the 24-hour period of a workday is:

Item	Energy Used (KWh)
Workday	0.4033144
Overnight	0.048
24-Hour Total	0.4513144

Next, we calculate the energy used during non-workdays, such as weekends, holidays and vacation. The system is assumed to be asleep on these days, and there are 1,440 minutes in 24 hours, so:

1,440 minutes x 3.2 watts = 4,608 watt-minutes

Converting to kilowatt-hours:

4,608 watt-minutes / 60,000 = 0.0768 KWh

In the EEP 2.0 model, we assume there are 240 workdays, and 125 non-workdays, so the annual energy consumed is calculated:

(Workday energy used x 240) + (Non-Workday energy used x 125) = annual energy used

(0.4513144 x 240) + (0.0768 x 125) = 117.915456 KWh

Our model uses a per-KWh energy cost of $0.0705 /KWh, which is the average of the commercial and industrial rates paid in the United States, according to the US Department of Energy.2

So, the annual energy cost for our example system is calculated:

117.915456 KWh x $0.0705 = $9.09

The resulting yearly energy cost is $9.09/year.

This chart shows energy costs for other Intel processors tested in the same system used in the above example:

Energy-Efficient Performance: A well-managed desktop Intel® Core 2 Duo PC costs about $10 per year for its energy usage.