Digital TV to bring surge in power consumption

The switch to digital television will lead to a big increase in energy consumption which could match the output of a gas-fired power station within ten years because consumers cannot switch off their new decoders. The surge in electricity consumption will offset energy savings elsewhere, posing a major challenge to the authorities in their efforts to curb greenhouse gas emissions.

This autumn, cable, satellite and terrestrial broadcasters have joined in a major effort to sell digital TV services in the UK. The industry is anticipating a large demand for integrated receiver decoders (IRDs) in the form of "set-top boxes". These can be used with any TV set, and will give access to interactive services such as "pay per view", home shopping and banking.

Manufacturers predict that five million IRDs will be installed in the UK by 2000. Further installations, combined with sales of dedicated digital TVs, could lead to at least 25 million households with digital TV reception by the end of 2008.

Different types of IRD will be needed depending on whether the consumer opts for a satellite, terrestrial or cable service. However, the UK service providers, BSkyB and On Digital, persuaded the service licensing authority, the Independent Television Commission, to accept IRD specifications which ensure the continuous flow of data even on standby

According to a study for the European Commission's Energy Directorate, DGXVII, the design permits "few significant power saving functionalities which can be closed down." 1 The standby power consumption will be identical to that when the TV is in active mode because the unit has to continue listening to incoming signals.

IRDs for receiving digital channels currently use around 16W, but this may rise to around 20W for the second generation of IRDs expected in the shops next year, as improvements in energy efficiency are offset by greater functionality. In comparison, today's most efficient analogue TVs consume just 1W on standby.

Unlike BSkyB, terrestrial servicing agent On Digital has adopted a conditional access system which means that the IRD can be switched off. However, when the system is left on standby, its running power of 16W drops by only 2W.

Broadcasters have pointed out that closing down the UK's network of analogue transmitters, once digital TV is fully established, will save around 50MW in power consumption, because digital transmission is more efficient.

However, the Consumers' Association, which has carried out research into IRD energy efficiency for the Commission, has warned that this gain could be "heavily compromised by the hidden energy agenda" associated with equipment to be installed in the home.

Even when the expected improvement in transmitter efficiency is taken into account, the use of 25 million IRDs in the UK by 2008, each with a power consumption of 16-20W, would require an additional 350-450 megawatts from the national grid - a figure comparable to the output of a gas-fired power station. The figure would be higher if many households opt for more than one IRD or integrated digital TV.

BSkyB is the first digital service provider in the EC to adopt a conditional access system which requires the IRD to be fully active in standby mode, but it is likely to be copied elsewhere. A second DGXVII study, nearing completion, will assess the energy consumption of current IRDs and integrated digital TVs and recommend the most efficient.

For white goods, DGXVII has a policy of mandatory efficiency standards and energy labels. But it may be reluctant to replicate this in the brown goods sector because of the pace of technological development. An alternative would be to develop a voluntary agreement with the industry, as it has already done for conventional TVs and video recorders.

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