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Are Energy Saving Fittings Efficient in a High Use Environment

By: John Rowlinson - Updated: 2 Jan 2013 | comments*Discuss
Energy Saving Light Bulbs Watts Light


Concerning energy saving light bulbs I have been told that they use a lot of power to start up and this makes them inefficient for places like halls and stairways where the light is not on long enough, if we are careful, to make energy saving.

I do not see this since an 11 watt bulb uses 11 watts per hour and the equivalent incandescent bulb uses 60 watts - or am I wrong?

(Mr Roger Booth, 14 January 2009)


It's an interesting question and quite difficult to answer exactly but here goes...

Compact Fluorescent Lamps (CFL's) have a transformer which is an inductive load. This means that it draws a surge of current when powered on which is what your friend is referring to - and in short term operation environments this could be significant on energy consumption. In fact this surge can cause other problems, for example when you are using a timer that will switch a number of lights at the same time. The cumulative surge from a number of CFL's can cause the relay in the timer to burn out. This is why they are not recommended for use with light sensors or relays.

You are right that an 11W lamp will consume 11W of power and generate the same light as a 40W incandescent fitting. The fact that it is powered on only for a relatively short period of time will slightly affect this power usage and make it less attractive power wise maybe consuming say 20W for 40W of light. This is really highly dependent upon the actual application and to verify this we would conduct testing. The 20W is a conservative 'guesstimate' on our part. It's still a significant gain, drawing only half the power and this is probably worse case.

Many low energy fittings have 'soft start' which means they warm up over time and have electronic transformers that do not have an inductive load. They would not be good for this application as by the time they have warmed up they would be turning off. They typically take 2-3 minutes to reach full intensity. They are used in many office type applications where a big surge in current would be a problem for switching and energy consumption.

One other thing to bear in mind is that the life of a fluorescent fitting will be far longer than that of an incandescent when the switching is frequent. The heating and cooling of the lamp filament in a traditional lamp would cause failure far more quickly than if it was left on permanently. CFL's do not suffer any significant degradation of life span with frequent switching. As you are probably referring to a commercial application the effort required to change the fitting will be a further consideration and the fitting may even be in a hard to reach location. A CFL should last at least 10 times longer in this type of application.

If you do choose a CFL for an environment where the on time is minimal ensure that you choose one that does not have soft start.

In our opinion an energy efficient fitting is ideal in this kind of location and, in fact, current building regulations stipulate the use of low energy fittings for all communal locations in new build residential apartments.

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