Light bulbs - various

Watts the difference: the end of the 100 Watt light bulb

New legislation that is aimed at boosting the uptake of energy saving devices comes into effect this month and as E&T explains it signals the end of the 100 Watt light bulb.

The days of selecting 60W, 80W or 100W light bulbs off the supermarket shelf could soon be a thing of the past thanks to a new European directive that came into force this month. Consumers will be asked to learn the lumen, which regulators hope will make energy-saving products much easier to market and explain to users.

The Eco-design Directive is not new legislation; it has been knocking around since 2005. Its prime purpose is to set out a framework that would be followed by the manufacturers of energy-using products, at the design stage, obliging them to reduce energy consumption and other potential negative environmental impacts that can occur through a product's lifecycle.

Amendments to the directive that were agreed last November are just coming into force.

The directive is not only aimed at light bulbs, but all electrical appliances. But with electric lights accounting for almost a fifth of our electrical use the focus is rightly aimed at these products.

Measurement is key to the work undertaken at the National Physical Laboratory, so Dr Paul Miller, Higher Research Scientist at NPL, is ideally placed to explain what the directive will mean to both consumers and manufacturers. 'From 1 September, the Eco-design Directive for Energy-using Products (EuP) will mean lighting becomes labelled in terms of lumens, instead of electrical watts. The lumen is a measure of the light produced, whereas watt measures the power put in.'

Miller explains that the reason for these changes to the labelling of lighting products has been the recent leaps forward in energy-efficient lighting technology.

'Lighting accounts for approximately 20 per cent of global electricity usage, so these advances mean a dramatic reduction in carbon emissions, and new innovations will only improve the efficiency and quality of lighting,' he said.

Dim view

However there has been confusion over how new products compare to old in terms of brightness, which many experts believe could be impeding their uptake. This is partly due to brightness being based on the electrical power input, or wattage. When incandescent bulbs were all pervasive, 100W equated to a particular light output, which people became used to, so it became a meaningful measure.

With various new light sources being developed and incandescent bulbs being phased out, this is no longer useful. A similar light output can be achieved from a 60W incandescent bulb as a 16W compact fluorescent lamp (CFL), the CFL just uses a quarter of the energy.

'As we move towards LED lighting and other new sources, which produce light in different ways, it makes sense to label light according to its lumen output, so we can clearly compare different technologies,' he says.

'This will make consumer choices, both on brightness and energy efficiency clearer. It will also facilitate the introduction of new energy-efficient products to market, as consumers will have a meaningful way of comparing new products with old. This will help reduce emissions from lighting and have positive impact on the innovative UK lighting business.'

Lumen is not a product that all consumers will be immediately familiar. The measure of brightness, the lumen, measures the luminous intensity of light emitted in all directions, taking into account the varying sensitivity of the human eye to different wavelengths, or colours, of light. It is defined in terms of the SI unit of light the candela, which measures power emitted by a light source in a particular direction. By multiplying the candela by the directions in which it is projected, a unit known as the steradian, the luminous intensity can be calculated, giving the total light emitted in all directions - the lumen.

Miller is confident that this change would not increase consumer confusion. 'There are those who argue that changing the system will be confusing for those used to watts, and that the lumen is something we can't relate to,' he explains. 'Naturally there will be an adjustment period, but the lumen offers sufficient advantages to make this worthwhile.

'First, it will provide a clear comparable system for understanding brightness and energy usage of all different light sources, and helping consumers make an informed decision about their purchase. Secondly, while people adjust to using lumens, the labelling will continue to use watts as a secondary measure, so people will still be able to use the system they are used to if they want.'

'Thirdly, the lumen measures light output, which is presumably easier for the man on the street to comprehend than the electrical input. So we anticipate people will quickly adapt to lumens, as they did some time ago to watts.'

As for the manufacturers they already measure their products in lumens, so current products are likely to continue to be manufactured as they are. However the new rules will make it easier to bring new products to market.

'Following the introduction of the new labelling it is likely that there will be a growing understanding of the lumen as a unit of measurement,' Miller adds. 'This will allow straightforward comparisons of brightness against energy usage, so customers can identify the most efficient bulbs without compromising light levels. This will help lighting manufacturers introduce new energy-efficient products, as customers will be able to make clear comparisons with existing products and informed purchasing decisions.

'However, there will be an understandable reluctance amongst some, who want to stick with what they know. To make this change work and reap the benefits it will bring to the introduction of new products, the lighting industry, along with consumer groups and retailers, need to make sure they clearly communicate - through packaging, marketing and the media - what the lumen is and why it is important.'

Miller explains how measurement underpins all of this and highlights NPL's work supporting the UK lighting industry. 'Lighting manufacturers need an accurate measurement of their product's brightness in order to meet safety standards and regulations. It is also necessary for ensuring the product fits its description.

'NPL helps manufacturers do this through its photometric calibration services, which measure luminous intensity, as well other metrics such as illuminance, luminance and correlated colour temperature. Measurements are performed using a high-accuracy photometer, which reflects the sensitivities of human eyes. NPL also supplies lamps to enable in-house calibrations. All of this is traceable to the candela - the SI unit for the luminous intensity of light.'

'Ensuring traceability of light measurement to the candela also allows light companies to guarantee that their measurements are accurate and that their definition of the lumen is the same as everyone else's around the world, facilitating international trade.'

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