In answer to the observations by David Cutter, and the article ’Street-wise street light’ there is one element missing.

In answer to the observations by David Cutter (Letters, 7 May), and the article ’Street-wise street light’ (News, same issue) there is one element missing.

That is the government’s intention to encourage consumers to move to energy-efficient lighting, particularly fluorescent, in the home, while dispensing with filament light bulbs.

However, the major aspect ignored is power factor. With filament lamps, the power factor is notably closer to the ideal of 1, where the voltage and current are in phase. This means power stations have an easier task to supply electrical energy efficiently.

Introduce fluorescent lighting, and the phase shift between the supplied voltage and current becomes significant. Consequently, the power station has to run at a higher power output, as apparent power, due to the loss of a near perfect power factor when referring to filament light units.

In other words, the loss of electrical energy has been shifted rather than being solved. While the ideal power factor is 1, where the load appears to behave as a pure resistive load, some fluorescent lamps can have a power factor of only 0.3.

I am moving to LED lighting as this has significantly less power consumption for the same light output, while having a significantly longer life than both filament and fluorescent lamps, and produces a close match to daylight without any undesirable loss of a near perfect power factor.

It is, at the moment, the obvious method of reducing power consumption without causing a major power factor problem.

Andrew Porter

Principal circuit design engineer, Ultra Electronics