The EPA's initiative was a response to the rapidly expanding population of PCs in the USA, where their energy consumption is projected to double from today's 5% of national commercial power consumption to 10% by 2000. Not only does each computer directly use some 250-300 watts of electricity, but large amounts of energy are needed for air conditioning to dissipate the 100 watts of heat produced by each unit.
In June 1992, the EPA announced plans for an Energy Star Computers programme to encourage PC suppliers to produce more energy efficient machines. The EPA's research had revealed that 30-40% of PCs are left on 24 hours a day, seven days a week - and even during working hours the typical PC is used only 20% of the time.
According to the EPA, the scope for energy saving amounts to a massive $2 billion per year. In environmental terms these amount to 20 million tonnes of carbon dioxide, 140,000 tonnes of sulphur dioxide, and 75,000 tonnes of nitrogen oxides.
The scheme came into force in June, with the "Energy Star" logo making its debut on products and in advertisements. Compliance is voluntary, but the EPA has gained support from over 65% of the US computer and monitor industry and 90% of the laser printer industry.
A compelling reason for this support is the federal government's promise that from October it will purchase only those computers which have qualified for the scheme, providing their performance is satisfactory. "The Administration is putting its money where its mouth is," said Vice-President Al Gore at the launch ceremony.
To gain the official logo, PC units must be able automatically to "power down" when not in use. In this condition the computer and monitor must not consume more than 30 watts of electricity apiece, compared with operational consumption of about 150 watts. Similar figures are set for printers.PCs meeting these standards have been manufactured by IBM, Apple, ICL, Intel and many other companies, and are now available in the UK. Within a year or two, says Howard High of Intel, "you won't be able to buy a non-energy efficient desktop computer."
"Power down" capabilities are a product of new power management software. This recognises when PC components are not in use and closes them down to a "sleep" mode with about one-tenth of the normal power consumption. A monitor on an energy-efficient ICL computer, for example, uses just 5 watts in its sleep mode - making something of a mockery of the EPA's standard, which was set at a high level to encourage manufacturers to support the initiative.
Hardware improvements are also having a significant effect on energy efficiency. These have arisen from the need to make batteries last longer in portable computers.
Screens based on cathode ray tube technology have been replaced by flat panel screens which use transistors. This cuts in-use consumption from around 150 to 37 watts.
In addition, circuitry has had to be made smaller and highly integrated for the portable market. This has brought the power consumption of the central processing unit (CPU) below 35 watts, in turn alleviating the need for internal cooling fans and thereby further reducing power consumption.
These advances represent the first generation improvements. Others, such as closing down parts of the system between key strokes, are just over the horizon, says Intel's Howard High.
Low power computers should make economic sense for companies. A traditional PC left on 24 hours a day will cost the average user $184 per year, according to Intel. First generation improvements can bring the cost down to $30 per year, while second generation units may ultimately reduce it to $3.5. ICL believes that the savings with its new range of PCs will be well over £100 per year, and the life of the computer is also increased.
The reduced operational costs of these PCs do not come without a capital cost penalty. IBM sells its energy-efficient PS/2-E computers with flat screen monitors at £5,000, almost double the price of alternative models. Purchasers "cannot justify these on primary energy alone," says Steve Walker of IBM. But IBM, Intel and ICL also supply energy-efficient CPUs with conventional monitors at a cost comparable to that of non-energy efficient models.
Meanwhile, the European Commission has begun work on a similar scheme under the EC's PACE programme on efficient use of electricity. A working group held its first meeting in what is likely to be a two-year process in March.