Computers
Product Definition/Scope of Product Category
We used a modified ENERGY STAR® definition of computers: A computer is defined as a device which performs logical operations and processes data. Computers are composed of, at a minimum: (1) a central processing unit (CPU) to perform operations; and (2) user input devices such as a keyboard, mouse, digitizer or game controller.[1]
Within this definition, however, we evaluated only non-expandable desktop and laptop computers. The scope of TopTen’s computer category does not include expandable desktops, workstations, thin clients or small scale servers. Also, the scope of TopTen’s computer evaluation does not include computer display screens. Display screens are vital to the operation of a computer but their energy use is not yet included in TopTen’s consideration, because the data are not available for the incremental power use of built-in screens within all-in-ones and laptops.
The scope of TopTen’s computer category divides computers into two separate TopTen lists of two sub-categories:
- 1. Non-expandable desktop computers
- 2. Laptops
Performance Criteria/Parameters Used
In developing the list of products that are eligible for TopTen USA we evaluated products based on the following criteria:
ENERGY STAR Computer Program Requirements v5.0.[2] All products eligible for TopTen’s listing must meet ENERGY STAR’s v5.0 program requirements. Only those products within ENERGY STAR’s qualified product dataset were evaluated. Among specific requirements within ENERGY STAR’s v5.0 specification, the following criteria were chosen for evaluating TopTen products:
w Annual energy use (kWh/year). We based annual energy use on ENERGY STAR’s definition, calculation and data for Total Energy Consumption (TEC). We ranked each of the two TopTen lists according to TEC. Below is ENERGY STAR’s definition for TEC:
Typical Energy Consumption (TEC). A method of testing and comparing the energy performance of computers, which focuses on the typical electricity consumed by a product while in normal operation during a representative period of time. For Desktops and Notebooks, the key criterion of the TEC approach is a value for typical
annual electricity use, measured in kilowatt-hours (kWh), using measurements of average operational mode power levels scaled by an assumed typical usage model (duty cycle—see Table 1). For Workstations, requirements are based on a TEC power value calculated from operational mode power levels, maximum power, and an assumed duty cycle.
It is also important to note that we chose to compare each TopTen model against the average TEC for each ENERGY STAR performance category (i.e. Category A, B, C, D) across all market segments.
Table 1. Operational Mode Weighting: Desktops and Notebooks
| Desktop |
Notebook (Laptop) |
|
| Conventional |
Conventional |
|
| Toff |
55% |
60% |
| Tsleep |
5% |
10% |
| Tidle |
40% |
30% |
Source: ENERGY STAR[1]
w ENERGY STAR classification. In addition to the primary ranking criteria, TEC, we also evaluated potential TopTen products based on ENERGY STAR’s performance categories (detailed below). Products were not ranked by these categories. Instead, we put a limit on products allowed from each ENERGY STAR performance category as well as each form factor type (i.e. laptop size, small desktop, all-in-one desktop). By doing so, the TopTen list includes a comprehensive list of products from a variety of consumer categories and does not give one particular group any specific advantages.
We divided the desktop market based on ENERGY STAR’s performance categories. The ENERGY STAR program has developed a very basic desktop computer classification scheme for its v5.0 specification. The product categories are intended to distinguish among computers with low amenity, performance and power needs and various higher performance machines that demand incrementally more power for operation. For the sake of simplicity, the classifications are based on information that can be readily obtained from product listings, such as the amount of physical memory installed in the computer, the number of processor cores, or the presence of a video card. The general criteria for desktop computer categories A through D are presented below.
Category A: All desktop computers that do not meet the definition of Category B, Category C, or Category D below will be considered under Category A for ENERGY STAR qualification.
Category B: To qualify under Category B, desktops must have:
Equal to 2 Physical Cores; and
Greater than or equal to 2 gigabytes (GB) of System Memory.
Category C: To qualify under Category C, desktops must have:
Greater than 2 Physical Cores.
In addition to the requirement above, models qualifying under Category C must be configured with a minimum of 1 of the following 2 characteristics:
Greater than or equal to 2 gigabytes (GB) of System Memory; and/or
A Discrete GPU.
Category D: To qualify under Category D, desktops must have:
Greater than or equal to 4 Physical Cores.
In addition to the requirement above, models qualifying under Category D must be configured with a minimum of 1 of the following 2 characteristics:
Greater than or equal to 4 gigabytes (GB) of System Memory; and/or
A Discrete GPU with a Frame Buffer Width greater than 128-bit.[1]
For non-expandable desktops, the TopTen list is divided into five (5) small desktops and five (5) all-in-one desktops. Within these two divisions, there are two (2) category A desktops, two (2) category B desktops and one (1) desktop that can come from the C or D category. If two or more laptops have the same typical energy consumption rounded to the nearest tenth, the result is a tie and both products will be displayed on the list under the same rank. This may occasionally result in lists with more than 10 products. See Table 2 for the full breakdown of each TopTen computer list.
Table 2. TopTen Product Selections Allocated by ENERGY STAR Category and Market Segment
| ENERGY STAR Category |
Desktop Market Segment |
Laptop |
|
| Non-Expandables |
|
||
| Small
|
All-in-one
|
||
| A |
2 |
2 |
2 < 13” Diag. Screen 2 ≥ 13” Diag. Screen |
| B |
2 |
2 |
4 |
| C |
1 |
1 |
2 |
| D |
N/A |
||
We also divided the laptop market based on ENERGY STAR’s performance categories. As with desktops, ENERGY STAR has established product categories for laptops based on their system configuration and performance.[2] The general criteria for laptop computer categories A through C are presented below.
Category A: All laptop computers that do not meet the definition of Category B or Category C below will be considered under Category A for ENERGY STAR qualification.
Category B: To qualify under Category B, laptops must have:
A Discrete GPU.
Category C: To qualify under Category C, laptops must have:
Greater than or equal to 2 Physical Cores;
Greater than or equal to 2 gigabytes (GB) of System Memory; and
A Discrete GPU with a Frame Buffer Width greater than 128-bit.
For laptops, the TopTen list is divided into four (4) category A laptops (including two (2) products with screen sizes less than 13 inches and two (2) products with screen sizes greater than or equal to 13 inches), four (4) category B laptops and two (2) category C laptops. If two or more laptops have the same typical energy consumption rounded to the nearest tenth, the result is a tie and both products will be displayed on the list under the same rank. This may occasionally result in lists with more than 10 products.
See Table 2 for full break down of each TopTen computer list.
Updates. We plan to update TopTen’s computer performance criteria on a quarterly schedule as technology changes and new product introductions warrant.
Test Methods
ENERGY STAR’s test method was used for evaluating the performance criteria listed above. (see Appendix A: ENERGY STAR Test Procedure for Determining the Power Use of Computers in Off, Sleep, Idle and Game Consoles in Sleep and Off). Under ENERGY STAR’s v5.0 computer requirements, all computers are required to have power supply efficiencies that comply with the following test protocols:
1) Internal Power Supplies. Generalized Internal Power Supply Efficiency Test Protocol Rev. 6.4.2:
www.efficientpowersupplies.org
2) External Power Supplies. ENERGY STAR Test Method for External Power Supplies:
www.energystar.gov/powersupplies
Also included under ENERGY STAR’s v5.0 computer requirements are total energy consumption requirements (ETEC). These are detailed in the ENERGY STAR Computer Test Method (Version 5.0), Section III.
Market Segmentation
We took the computer market and broke it down into desktops and laptops. Within the desktop category, we further divided the market into two primary groups as detailed below.
Desktops
We used ENERGY STAR’s definition for desktop computers: A computer where the main unit is intended to be located in a permanent location, often on a desk or on the floor. Desktops are not designed for portability and utilize an external computer display, keyboard and mouse. Desktops are designed for a broad range of home and office applications.[3]
We categorized desktop computers into two primary groups: (1) expandable desktops and (2) non-expandable desktops.
Expandable Desktops
Expandable desktop computers include two sub-categories: (1) consumer expandable and (2) business expandable computers. Details of these two sub-categories are provided below. Both sub-categories have expandability requirements as well as attributes that differentiate between consumer and business marketed machines.
Due to the wide variety of configuration possibilities and the ability to easily customize expandable desktops, determining a methodology for ranking this group of desktops has proven difficult and the inclusion of a TopTen list of expandable desktops has been delayed until the next update.
Consumer Expandable
This category of computers dominates the desktop market driven by consumers’ preference for low cost and expandability. These units tend to have larger power supplies than their less expandable counterparts, to accommodate other components that may be added after purchase. To be classified as “consumer expandable,” a desktop computer must have the following components:
At least two 5.25” bays and two 3.5” bays
At least three full height PCI or PCI Express (PCIe) expansion slots (primarily to serve customers’ desire for additional multimedia capabilities)
Can be marketed as a business computer, but must support a home operating system (e.g. Mac OS X or any of the varieties of Windows Home Edition)
Business Expandable
To be classified as a business expandable, a desktop computer must have the following components:
At least one 5.25” bay (not mobile or slimline) and two 3.5” bays
At least two low-profile or full-height PCI or PCIe expansion slots
Computer models targeted to business customers will also tend to have at least two of the following attributes as well:
Remote diagnosis, repair and software updates
Remote power management
High platform stability: >1 year product update cycle
Support staff that are specifically trained and equipped with tools to support computing in a business environment
For Windows PCs: Support for XP Professional, Vista Business or Windows 7 Professional or any x64 editions of these operating systems
For example, all systems with Intel vPro technology would qualify for the Business category.
Non-expandable desktops
Our first TopTen computer list is for non-expandable desktops. Non-expandable desktop computers include two sub-categories: (1) all-in-one and (2) small computers:
All-In-One Desktops
All-in-one computers are desktop computer systems in which the computer and computer display function as a single unit. All-in-one computers include a monitor that is physically integrated with the central processing unit, and the computer is not intended for battery-operated, mobile usage (which would make it a laptop instead). These computers provide unique amenity for space-constrained locations where consumers value the lack of cabling or the ability to easily transport these units to other locations. We chose to pick five models within this category to formulate a list of 10 models for non-expandable desktop computers (all-in-one and small).
Small Desktops
We defined small desktop computers as all desktop computers that do not meet the definition of All-in-one or Expandable computers. Small units would tend to dominate a TopTen list without additional selection criteria, given that smaller, less expandable systems are commonly designed with more efficient mobile components, smaller power supplies and generally lower overall power levels. We made no effort to distinguish among the many terms used by the industry to define products that would tend to be selected in this category, including small form factor, mini and nettop. We chose to pick five models within this category to formulate a list of 10 models for non-expandable desktop computers (all-in-one and small).
Laptops
Our second TopTen computer list is for laptops. We used ENERGY STAR’s definition for laptop (or notebook) computers: A computer designed specifically for portability and to be operated for extended periods of time either with or without a direct connection to an ac power source. Notebooks must utilize an integrated computer display and be capable of operation off of an integrated battery or other portable power source. In addition, most notebooks use an external power supply and have an integrated keyboard and pointing device. Notebook computers are typically designed to provide similar functionality to desktops, including operation of software similar in functionality as that used in desktops.[1]
Data Sources and Quality Assurance
We used manufacturer reported data from the EPA ENERGY STAR website:
http://downloads.energystar.gov/bi/qplist/computers_prod_list.xls
Recent publicly available datasets from the U.S. EPA ENERGY STAR program were used to evaluate the power consumption of different computer categories in their various modes of operation. Because a consensus test procedure does not yet exist to describe the active mode of operation – the time that the computer is actively processing commands for the user – typical power consumption values for this mode of operation are not available. The other modes of operation included are Idle, Sleep and Standby. Idle mode in particular dominates the energy use of a computer.
TopTen reviews its computer listings as well as ENERGY STAR’s dataset frequently. Spot checks on select listed products are often conducted to ensure quality assurance of these data. Full laboratory testing is recommended prior to updating listings for products that claim to be unusually energy efficient relative to other similar models.
Market Availability
In order to be qualified for TopTen, a model must be listed on its manufacturer’s website as a current model. In addition, we ensured that the model is available through online vendors when not sold directly on the manufacturer’s website.
Families of Similar Products
To prevent slight variations of the same, highly efficient product from securing the majority of available recognition slots, we combined similar products into a single family of models within each ENERGY STAR performance category (i.e. Category A, B, C, D). Across different performance categories, on the other hand, products from the same product family were allowed to qualify for TopTen listing. This is most noticeable in the expandable desktop category where products from the same product family are listed in a wide array of slightly different configurations.
For this reason, we currently do not attempt to rank the expandable desktop category.
In general, members of the same product family will originate from the same original manufacturer (though may have different brands). In desktops, they will fall in the same market segment: small, all-in-one, consumer expandable or business expandable. They will be functionally and cosmetically similar, operating with the same motherboard and chipset, but with slight differences in processor speed, amount of memory, number and types of optical drives, or size of hard drive.
Product Ranking
We ranked products on the basis of annual energy use. Models with identical annual energy use are given the same ranking.
Glossary
ENERGY STAR Definitions
Computer. A device which performs logical operations and processes data. Computers are composed of, at a minimum: (1) a central processing unit (CPU) to perform operations; (2) user input devices such as a keyboard, mouse, digitizer or game controller; and (3) a computer display screen to output information. For the purposes of this specification, computers include both stationary and portable units, including desktop computers, gaming consoles, integrated desktop computers, notebook computers, small-scale servers, thin clients and workstations. Although computers must be capable of using input devices and computer displays, computer systems do not need to include these devices on shipment to meet this definition.
Desktop Computer. A computer where the main unit is intended to be located in a permanent location, often on a desk or on the floor. Desktops are not designed for portability and utilize an external computer display, keyboard and mouse. Desktops are designed for a broad range of home and office applications.
Idle State. The state in which the operating system and other software have completed loading, a user profile has been created, the machine is not asleep and activity is limited to those basic applications that the system starts by default.
Laptop Computer. A computer designed specifically for portability and to be operated for extended periods of time either with or without a direct connection to an ac power source. Notebooks must utilize an integrated computer display and be capable of operation off of an integrated battery or other portable power source. In addition, most notebooks use an external power supply and have an integrated keyboard and pointing device. Notebook computers are typically designed to provide similar functionality to desktops, including operation of software similar in functionality as that used in desktops.
Off Mode. The power consumption level in the lowest power mode which cannot be switched off (influenced) by the user and that may persist for an indefinite time when the appliance is connected to the main electricity supply and used in accordance with the manufacturer’s instructions. For systems where ACPI standards are applicable, Off Mode correlates to ACPI System Level S5 state.
Sleep Mode. A low power state that the computer is capable of entering automatically after a period of inactivity or by manual selection. A computer with sleep capability can quickly “wake” in response to network connections or user interface devices with a latency of ≤ 5 seconds from initiation of wake event to system becoming fully usable including rendering of display. For systems where ACPI standards are applicable, Sleep mode most commonly correlates to ACPI System Level S3 (suspend to RAM) state.
Typical Energy Consumption (TEC). A method of testing and comparing the energy performance of computers, which focuses on the typical electricity consumed by a product while in normal operation during a representative period of time. For Desktops and Notebooks, the key criterion of the TEC approach is a value for typical annual electricity use, measured in kilowatt-hours (kWh), using measurements of average operational mode power levels scaled by an assumed typical usage model (duty cycle). For Workstations, requirements are based on a TEC power value calculated from operational mode power levels, maximum power and an assumed duty cycle.
Further Information
Key Publications and Data Sources
http://efficientproducts.org/
ENERGY STAR Program Requirements for Computers. Version 5.0. Available at:
How Low Can You Go? A White Paper on Cutting Edge Efficiency in Commercial Desktop Computers.
Prepared by: Nathan Beck, Peter May- Ostendorp, Chris Calwell (Ecos) | Baskar Vairamohan, Tom Geist (EPRI). March 2008. Available at:
Laptop Computers: How Much Energy Do They Use, and How Much Can We Save? Highlights of project
managed by Noah Horowitz, Sr. Scientist NRDC. Prepared by Suzanne Foster and Chris Calwell of Ecos Consulting. September 2003. Available at:
http://www.efficientproducts.org/reports/computers/NRDC_laptop_efficiency_4-pager.pdf
[1] For full description see: http://www.energystar.gov/ia/partners/prod_development/revisions/downloads/computer/Version5.0_Computer_Spec.pdf
[1] In a future revision of the TopTen list for computers, we recommend the creation of an additional performance category beyond Category D. In our review of the ENERGY STAR dataset, it was clear that ENERGY STAR’s current definition for Category D has allowed most of the listed models to qualify by including more memory, but not by including the type of graphics and multimedia capabilities sought by gamers and multimedia content creators.
[2] ENERGY STAR classifies laptops as “notebooks”
[3] For full description see: http://www.energystar.gov/ia/partners/prod_development/revisions/downloads/computer/Version5.0_Computer_Spec.pdf
[1] Ibid.
[1] we excluded “and (3) a computer display screen to output information.” from ENERGY STAR’s original definition for the purpose of this document.
[2] available at: http://www.energystar.gov/ia/partners/prod_development/revisions/downloads/computer/Version5.0_Computer_Spec.pdf
