Wattage comparison – Goodbye Watts – Hello Lumens

Not so very long ago, when incandescent bulbs ruled the roost, choosing the right light bulb based on brightness was incredibly simple, as it was all done in watts. And what’s a watt? Well it’s a measure of energy transfer (named after James Watt, the pioneer of steam engines), but that was always irrelevant. For years, everyone knew that 60 watts meant standard room lighting, 40 watts was a bit dingy, 100 watts was nice and bright for kitchens and bathrooms, and anything brighter than that was best left for surgeons and interrogators.

Getting rid of confusion

Everything’s changed now though, with the decline of incandescent bulbs and the rise of energy-saving and LED bulbs. All of a sudden, the wattage has changed drastically while the brightness has stayed the same, leading to a good deal of confusion. When energy-saving bulbs were first introduced, manufacturers initially dealt with this by printing the wattage the bulb was equivalent to on the packaging, e.g. ‘11w – 60w equivalent’. You can find a table of the more common equivalents at the bottom of the page, which is a reasonably good guide to the likely brightness level of your bulbs (not all energy-saving bulbs give off quite the same light, but then neither did incandescents). However this isn’t the whole story.

While it’s easy to make a rough comparison between incandescent and energy-saving bulbs, lighting is not just about these two types of bulb any more. There are also now various different types of LED bulb, not to mention halogen bulbs, and assorted tubes, so it’s virtually impossible to find a measure of energy that can be applied to all bulbs and still mean anything to the layman. Which is where lumens (lm) come in.

What is a lumen?

A lumen is a measure of the light given off by any light source that can be perceived by the human eye (i.e. not including the invisible wavelengths). Lumens basically cuts out any measurement of how much energy it takes to produce a given amount of light, and just measures the light given off. This is like your car’s speedometer measuring how fast you’re going, rather than the amount of energy it takes to get you to that speed, and is a far more sensible way of defining light levels.

You’ll need to get used to Lumens too, as EU legislation now states that the lumen value of a particular bulb must be printed most prominently on packaging. It’s not hard to see watts and equivalent wattages going the way of pounds, ounces and the dodo in the fullness of time. So how do lumens work then?

Rough equivalents

As a rule of thumb, lumens are very roughly equivalent to the incandescent wattage times ten, plus a little bit, so that a 450lm light source is roughly equivalent to an old 40 watt bulb, while an 800lm light source is similar to a 60 watt bulb. Comparisons for the most common sizes are in the table below.

Get ahead

Due to the huge variety of possible light levels available from new generation energy-saving and LED bulbs, it’s a good idea to get into the habit of thinking in lumens. It’s also a very good idea to buy spares when fitting multiple light sources in the same space, as wattage is now no longer a guarantee that a bulb will be the same level of brightness. Plus because bulbs lasts so much longer now, if one of your bulbs looks wrong, you won’t be stuck with it for months, but maybe for years!


Energy-saving bulb Incandescent Bulb Average Lumens
4-7 Watts 25 Watts 300
9-11 Watts 40 Watts 450
13-16 Watts 60 Watts 800
18-20 Watts 75 Watts 1100
22-25 Watts 100 Watts 1500

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Energy Saving Bulbs Explored

Energy saving bulbs have fairly quickly become “standard” light bulbs over the last decade. The inefficient filament bulbs of old are now hard to find, and the UK has taken a more aggressive approach to the phasing-out of environmentally-unfriendly bulbs than Europe in general.

The UK government is at the driving seat of the initiative, pushing through legislation that sped-up the process massively – starting with the putting an end to light bulbs greater than 100W.

It’s fair to say that energy saving light bulbs are the norm here in the UK, but there’s still a lot of murky terminology that could do with clearing up. One of the core issues facing the bulb buyer is how these bulbs are marketed.

Low energy or energy saving – is there a difference? There is actually none at all, they are merely two ways to express the same types of technology. A much more accurate way to check out how energy efficiently a lightbulb runs is to compare the actual wattage of the bulb to the equivalent filament wattage.

Although low-energy bulbs are used virtually everywhere throughout the UK, bulb packaging still largely relies on the legacy measurements, generally 40W, 60W or 75W. Having said that, by law packaging is now required to show the lumen value at twice the size of the wattage, therefore drawing attention to the light value rather than the power involved.

Standard energy saving bulbs can roughly be split into four types – GLS, Candles, Golfballs and Reflectors. The most familiar of the quartet is the GLS, which stands for General Lighting Service. These bulbs use the stereotypical lightbulb design, for a traditional look.


Our Energy Saving Halogen GLS Clear is available in wattages equivalent to 28W, 42W, 70W or a super-bright 105W, while using 30 percent less power than the incandescent type. With a look just like the old type, they’re designed to act as a straight swap for bulbs that are no longer available, and come they come with either a bayonet or screw fitting.

This GLS bulb lasts for on average 2,000 hours, but lower-power GLS bulbs can last for even longer. The Value Low GLS bulb is rated at either 11w or 15w, and is rated for a huge 10,000 hours of use. However, this type of bulb doesn’t support dimming, while the previous type does.


The golfball type of bulb takes the GLS shape and makes it more space-efficient, resulting in a rounded dome shape. The key benefit to this type of lightbulb is that it lets the whole thing get a lot smaller.

Our standard Clear Golfball Halogen Energy Saver comes with both standard-size and small-size fittings, using both the bayonet and screw type. This makes it perfectly suitable for smaller light fittings that either don’t offer the space for a full-size bulb, or look a little odd with one.

Like the GLS type, there are standard power energy saving bulbs that offer around a 30 percent energy efficiency improvement and lower-powered options that increase the energy efficiency and stamina, to around 10,000 hours. Once again, though, this higher-efficiency type doesn’t support dimming.

Candle Bulbs

For fittings that require a more slender bulb to look right, you should consider the candle type, which has its most bulbous part early on in the bulb’s body rather than right at the end.

Our clear-bodied Energy Saving Halogen Candle comes in both standard and small screw/bayonet fittings, letting them slot into smaller light fittings, like the golfball type. In the incandescent wattage standard, 60W, 40W and 25W bulbs are available, while using just 42W, 28W and 18W of power, respectively.

A more efficient option is here too. Although the “B” rated energy efficient candles cost around twice the price of the standard clear type, they provide greater energy efficiency and up to around four times the lifespan. The quality of light is a little different, though, with a translucent finish that gives warmer output.


The last energy saving bulb type to cover is the one that arguably has the greatest functional effect upon light output – the reflector bulb. Here, a significant proportion of the bulb is coated in reflective material, giving the bulb far more directionality than the standard type.

These types of bulb are often used in spotlights. Our Halogen reflectors come with both small and standard screw fittings, the most common type for this sort of light. Due to this sort of usage, the reflector is available as a high powered 70W (with over 100W output by incandescent standards) bulb, although this power is only available in the standard-size fitting.

Alternatively, the Long Life reflectors offer truly staggering stamina, rated for up to 15,000 hours of use. Grade A energy efficiency means that the small screw 7W model pumps out the equivalent of 35W of power, while the 11W and 15W models crank out 60W and 75W a piece. They cost a little more than regular bulbs, but when they offer such jaw-dropping performance, it’s worth the extra.

Need a few more options? Take a look at our full selection of Energy Saving Bulbs.

Looking for more news, information or inspiration? Try our Lighting Advice section.