Nowadays, it’s nigh-on impossible to buy a luminaire from the DIY sheds or a high-street retailer which doesn’t have a GU10 cap. 12v lamps seem to have had their day as far as the mass retailers are concerned.
It isn’t difficult to match the light output of a 20W or 35W halogen GU10, so we have only tested LED lamps that claim equivalence to a 50W.
The European DIM2 regulation says that to make this claim, the LED GU10 lamp must emit more than 345 lm in a 90-degree cone. The total lumen output, including light that falls outside this cone, may be considerably higher. Some of the lamps tested emit over 500 lm so they would clearly be seen as an improvement if you retrofitted them in an existing installation of halogen GU10 (with the same beam width).
We’ve asked several experts, and our understanding is that all products currently on the market must conform to DIM2. But we regularly hear of lamps that don’t.
The problem for Joe Public is that some lamps don’t state on the box whether the lumen output quoted is the total emitted or within the 90-degree cone. Some quote both figures. Reputable manufacturers use phrases like ‘usable lumens’ or ’90-degree cone’ so you know what you are buying. However, until all suppliers mark their packaging clearly, it is impossible for the purchaser to make fair comparisons between the different products. No wonder people buy the cheapest or the one quoting the biggest lumen value.
The situation is made worse because there is no effective policing of the market. This, in effect, benefits the poor quality, low-cost suppliers to the detriment of the manufacturers of good-quality lamps.
One last point to make is that a 90-degree cone isn’t really what you would call a spotlight. For the non-trigonometrists amongst you, that’s a two-metre wide illuminated patch from a lamp one metre away.
If you are as confused as I am by all the test standards that cover LEDs, there is a useful summary on the LIA website. Look for Technical Statement TS01. It’s nine pages long and covers existing and proposed European and US regulations and guidance.
None of the 11 lamps we’ve tested here had a particularly high power factor. The best was Osram at 0.88 and the poorest were the Aurora and Bell at 0.52. Why does this matter? Because it means that you are drawing more current than might be apparent from just looking at the wattage. An electrician complained to me about this because he had to resize all his fuses in a (large) domestic house purely because of equipment with a poor power factor.
Before you buy the lamps, you should check what the beam looks like. Some have coloured edges or don’t have a smooth gradation of light from the centre to the edge. The three on the left of the main photo for this article are all rated at 2700K and the one on the right is rated at 3000K.
Summary of results
We were pleased to see that, generally, the performance was as claimed. We measured the total light output.
Note that we tested just one lamp from each supplier. There are always tolerances in manufacturing and so the lamp you buy may not perform exactly as the one we tested. However, these lamps are made by the million; it would be surprising if they varied that much.