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In my previous post, I looked at the European Union (EU) Energy Star specifications for computers. This week, I decided to apply the specifications to a computer that is currently available to purchase; I walk through the calculations used to determine whether the computer meets the Energy Star requirements as set out in Commission Decision 2009/489/EC.

Inside Strasbourg cathedral

The computer I have used in this example is the Apple iMac, 21.5 inch, 3.06GHz (model MB950). I have used the values for power consumption from the Energy Star Product Database.

Apple also publishes power consumption information for the iMac in their Environmental Report. I was interested to note that values for idle power consumption in the Energy Star database and the Apple report are different. The values for power consumption in off mode and sleep mode are the same. I suspect the difference in idle power consumption values is due to differences in the definition of idle.

I decided to use the power consumption values from the Energy Star database, as they are more likely to have been measured in accordance with the specification.

Here are the details of the iMac I used from the Energy Star database:

• Category: B
• Idle mode (W): 28.1
• Off mode (W): 0.8
• Sleep mode(W): 1.9
• E_TEC (kWh): 103.0
• CPU: Intel Core2 Duo
• Core speed (GHz): 3.1
• System memory (GB): 4
• Discrete GPU: no
• Hard drives: 1
• Operating system: Mac OS X

This iMac falls within category B in the Energy Star specifications. The specifications provide four different categories for desktop computers based on their capabilities. To be classed as category B, the computer must have equal to two physical cores and two gigabytes of system memory.

To qualify for Energy Star status, a category B desktop computer must have a typical energy consumption equal to or less than 175kWh per year. The typical energy consumption limit can be increased by adjustments made for additional system memory, a discrete GPU, and additional internal storage. The iMac we are looking at does not meet the requirements for any adjustments based on additional system memory, a discrete GPU, or additional internal storage.

The formula for calculating the typical energy consumption of a desktop computer is set out in the specifications. The formula calculates the amount of power the computer would use over the year, based on the power it uses in different states and the average amount of time spent in those states:

E_TEC = (8760/1000) x (P_off x T_off + P_sleep x T_sleep + P_idle x T_idle)

The P-values represent power consumption measured in watts.

The T-values represent time measured as a percentage of the year.

The amount of time the computer spends in each state (the T-values) is set out in the specification. For a desktop computer the percentage of the year spent in each state is below:

• Off: 55% (T_off = 0.55)
• Sleep: 5% (T_sleep = 0.05)
• Idle: 40% (T_idle = 0.40)

The power consumption for each state (the P-values) are determined by measuring the particular computer in accordance with the specification. I have used the values from the Energy Star database for the iMac:

• Off mode: 0.8W (P_off = 0.8)
• Sleep mode: 1.9W (P_sleep = 1.9)
• Idle mode: 28.1W (P_idle = 28.1)

When we put the P-values for this iMac and T-values for desktop computers into the formula, it looks like this:

E_TEC= (8760/1000) x (0.8×0.55 + 1.9×0.05 + 28.1×0.40)

E_TEC= 103.1

To meet the Energy Star requirements, this iMac needs typical energy consumption of of 175kWh or less. At 103.1kWh, the iMac meets the Energy Star requirements.

I was interested to note that the Energy Star database gives an E_TEC value for this iMac of 103.0, whereas my calculations came out as 103.1. I’m not sure where this discrepancy comes from, but in either case, the iMac’s typical energy consumption is well within the requirements.

This week I have been looking at the EU Energy Star Programme’s specifications for computers. The Energy Star Programme identifies energy efficient computers and office equipment.

Le Monde Apple en direct, Strasbourg

The most recent specifications for computers came into effect on 1 July 2009. The specifications set out the requirements that a computer needs to meet to use the Energy Star label. The most recent specifications for computers are set out in Commission Decision 2009/489/EC.

Here is a summary of the requirements for desktop computers (such as Mac Pros), integrated desktop computers (combined computer and monitor, such as iMacs), and notebook computers (such as MacBooks). The specifications go into a lot of detail for different computer set ups and capabilities. This is a broad overview of the numbers.

Desktop and integrated desktop computers must have a typical energy consumption of 138 – 204 kWh per year or less. This is based on the computer spending 55% of time off, 5% of time in sleep mode, and 40% of time idle.

Notebook computers must have a typical energy consumption of 40 – 88.5 kWh per year or less. This is based on the computer spending 60% of time off, 10% of time in sleep mode, and 30% of time idle.

The energy consumption requirements appear to be baseline figures. They do not take into account any active use of the computers.

In addition to meeting the energy consumption requirements, computers must also have power management enabled. The display must sleep after 15 minutes of user inactivity, and the computer must sleep after 30 minutes of user inactivity.

After publishing my post about European Union (EU) policy on stand by power consumption last week, I discovered that the EU directive it was based on had been replaced. This left me wondering whether the regulation on stand by power consumption was still applicable.

Strasbourg from above

Last week, I learnt that the EU sets limits on the amount of power equipment can use when it is in stand by mode and off mode. These limits were introduced through Regulation 1275/2008. This regulation was implemented under Directive 2005/32/EC.

I have since learnt that Directive 2005/32/EC has been repealed, and replaced by Directive 2009/125/EC. Both of these directives aim to reduce the energy consumption and environmental impact of a range of products. The new directive expands the scope of the old directive to include a wider range of products.

The regulation on stand by power consumption was based on the old directive. But, the old directive has been replaced. Is the original regulation still in force?

After much searching, I have not been able to find a definitive answer. But, here are my thoughts.

Directive 2009/125/EC states that references to the repealed directive will be construed as references to the new directive. This suggests to me that the regulation on stand by power consumption will continue, but now refer to the new directive instead the old one.

On a practical note, the new directive aims to achieve the same goals as the old directive, but covers a wider range of products. The regulations implemented under the old directive go some way to achieving those goals for specific groups of products. It seems counterproductive for the new directive to undo those regulations.

Is Regulation 1275/2008 on stand by power consumption still effective under the new directive? I’m not sure, but if I had to guess, I would say yes.

My exploration of European Union (EU) policy on computer energy consumption got off to a disappointing start last week. This week, I have discovered the EU Ecodesign concept, and have delved into the regulations relating to stand by power consumption for electrical items.

Building detail, Strasbourg

Last week, I set out to learn what EU policies were in place on computer energy consumption. I was disappointed when all I found was the EU Energy Star programme.

This week, I decided to escape the confines of the Europa pages, and see what Google could turn up for me. I ultimately ended up back on the Europa web site, but with far more interesting results.

I discovered the EU Ecodesign concept. Ecodesign seems to be a name the EU has applied to a collection of initiatives and legislation that aim to reduce the energy consumption and environmental impact of a range of products.

The overall framework for the Ecodesign principles was established by EU Directive 2005/32/EC. While the directive provides a foundation for Ecodesign, the details of how Ecodesign applies to specific products are contained in separate regulations.

I decided to look at Regulation 1275/2008 which sets out the requirements for stand by mode and off mode of household electrical and electronic equipment. The list of equipment it applies to covers most of the things you have plugged in to power sockets in your home, including computers.

The regulation sets limits for the energy consumed by equipment when it is in stand by mode and off mode. As far as I can tell, the limits apply to equipment that is sold in the EU. The requirements will be phased in over 4 years, starting in December 2008.

Here is a summary of the requirements.

1 year after the regulation is in force (December 2009):

• Power consumption in off mode must be 1 Watt or less;
• Power consumption in stand by mode which allows reactivation must be 1 Watt or less;
• Power consumption in stand by mode which allows reactivation and displays information (such as a clock) must be 2 Watts or less.

4 years after the regulation is in force (December 2012):

• Power consumption in off mode must be 0.5 Watts or less;
• Power consumption in stand by mode which allows reactivation must be 0.5 Watts or less;
• Power consumption in stand by mode which allows reactivation and displays information (such as a clock) must be 1 Watt or less.

The regulation also provides that equipment that is connected to mains power must have a stand by or off mode, and must also have a power management function which automatically switches the device into stand by mode or off mode when it is not being actively used.