/ Home & Energy

Energy saving light bulbs – turned off by slow light-up times?

Energy saving light bulbs

Are you turned off by the sluggish light-up times of energy saving light bulbs? Our latest lab test results suggest that this problem may be fading, but it all depends on how good the bulb is.

The most common type of energy saving light bulb, compact fluorescent lamps (CFLs), have been plagued by frustratingly slow warm-up times in the past – as many of you have shared in previous light bulb-themed Conversations.

The bulb in my bathroom is one such excruciating example. During the mini-test I conducted last night, it was over a minute before it emitted anything more than a dull orangey light.

Our rather more scientific, lab-based test findings, however, do make for better reading. The top performing CFLs are brighter, able to withstand being switched on and off 30,000 times and give out a fair amount of light immediately after start-up.

LED bulbs still king

During our tests, we checked how bright the bulbs were when first turned on, and then at intervals to ensure measured brightness met what was promised on the packaging. Our Best Buy CFL light bulbs didn’t drastically dim after 5,000 hours – the equivalent of five years’ use – and emitted good levels of light.

Start-up times still aren’t great, though. The worst performer emitted no light at all after three seconds. And even the best CFLs only achieved less than half their claimed brightness when they were first switched on.

For instant bright light, you’ll need to turn to more advanced LED lighting – but be prepared to pay a premium for it.

How much for a light bulb?!

The two LED light bulbs we tested were in a league of their own when it came to efficiency and providing immediate light.

But you’ll have to shell out at least £20 – and for one, nearly £40! – to bask in the LED radiance of these bulbs. Energy efficiency savings aside, that’s a lot of upfront cash to shell out on a single light bulb, particularly when we’ve become used to the likes of cheap ‘three-for-a-pound’ supermarket offers.

Your light bulb bugbears

Overall, it looks like energy saving light bulb technology has improved and it’s good to see more candle and rounded bulb-shape varieties available too.

Yet, as the next phase-out stage for 60W traditional light bulbs beckons, other small but significant daily usage problems remain for many of us – like the potential incompatibility problems posed by dimmer or timer switches, for example.

Personally speaking, until the price of LED light bulbs come down, it looks like I’ll have to wait for my CFL light to fully kick in after switching it on. Though I’ll certainly be pickier when I have to choose a replacement. Are you willing to pay more to enjoy instant, long-lasting light?

If you’re a Which? member, you can view the full test results of our Best Buy light bulbs here.

Craig M says:
11 July 2011

Sadly I find the Which? Report really inadequate in several respects. The basic Which? view of the light bulb seems to be that you turn it on, it doesn’t really matter if it takes a few seconds to get going and then you leave it on for a long period. Many lightbulbs in fact are used on for a brief time: Security lights, light in a toilet (we men can often finish our business long before the light allows you to see what you’re doing), light in a room on for the 30 seconds it might take for you just to pop in to pick something up, etc. Here the warmup time which can be surprisingly protracted is a major problem, particularly when what light is produced tends to be at the red end of the spectrum making effective visibility much poorer. The measured light level may come out to be quite high since using broad-spectrum photometric measurements things look much better than they are if you use a measurement at the middle of the spectral band (green light, where our eyes have maximum sensitivity).
The second problem I have is that if I check low-energy lightbulbs for the light output in green and compare that with old-fashioned tungsten lightbulbs then they generally produce about 15% less light than you would expect from their wattage marking (so you get about 50 W out of a 60 W marked long life bulb).
There is one way out of this which I do not think as mentioned and this is to use halogen lightbulbs which turn on instantly but use a relatively high amount of power, are also very expensive and seemed to last even fewer hours than the old-fashioned tungsten lightbulbs.

Low-power lightbulbs are one of the major technological defeats of recent years. Homoeopathy may be popular but lightbulbs producing homoeopathic levels of light are simply not fit for purpose.


How much light do you need to go for a pee? I’ve got one of the freebe CFLs in our smallest room, and at 7W it’s probably brighter than actually needed, but is still 1/5 of the cost to run than the standard 40W Tungsten that I took out.

Although at first on, it’s probably only equivalent to a 40W, before getting to it’s full 60W equivalency; exactly how bright do you need it?!

Or, put another way, if you’re in the ‘reading’ room for more than a minute, the CFL is nearly up to full brightness; perfect for that monthly computer mag…

PerryM says:
11 July 2011

Keep a lookout in Lidl for LED ‘bulbs’ – I’ve bought several ‘spotlight’ types over the last year or two for less than a tenner each and they are all working fine with no apparent intereference problems. One is in my bedside light and provides the only light for reading, so I think I would have noticed any adverse strobing effects. I do know from my job as a video engineer that this is very subjective to the individual.
I also know from my video experience that neither LED or CFL lamps will match tungsten for best colour rendering, faces in particular will always be unflattered by the light they produce.

IanP says:
11 July 2011

Where you are coming from Stan Jacos? You are advising the use of candles when everyone knows that they can cause fire. That’s irresponsible! And you will be telling us next that cooking with microwaves is safe. The Russians banned it 40 years ago!

stanjackos says:
12 July 2011

I am being very polite when I say that you have managed to get every single point in your post WRONG! First of all its “stanjackos” not “stanjacos” (You need better glasses). Secondly, the comment which refers to using wooden tools and candles went straight over your head. It was a a sarcastic comment refering to the fact that nearly everything in the modern house can be harmfull to your health in a cumulative way (even microwaves), ergo, anybody who worries about the minute danger posed by CFLs are paranoid and should eliminate everything that contains hazardous materials or functions. It was an hypothetical comment that I assumed anybody with more than 2 brain cells would understand. Obviously I was wrong. Thirdly, you are totally incorrect when you say that the Russians banned Microwaves 40 years ago, Micowaves were indeed banned in 1976 (35 Years ago) on information based on flawed research. This ban was lifted after Perestroika in the late 80′s and microwaves are now widely used in Russia.

Finally, candles are not dangerous, they are inert cylinders of parrafin wax with a vegatable based wick. It is the careless and foolhardy that cause problems not the candles.

Gidster says:
11 July 2011

I am afraid I still don’t understand whether it is more cost effective to buy LED ceiling spots(compared to ‘regular’ 50w Halogens)? I have a lot of these ceiling down lights and I would really love to know if it will pay us to switch over to LED now in total (ie a big bang changeover) or only as and when the Halogens fail. Or even, dare I say it, at all! Clearly at £1 or so for a Halogen compared to £12 – £14 for an LED there is an immediate difference in the puchase prices. But as the LEDS run at 7w compared to the 50w GU10 Halogens I wonder how many hours of the light being on do you need to reach the breakeven point? And of course there is the fact that at 50,000 hours of predicted life for an LED you should not have to replace them as much as the 1,000 hour Halogens. Can anyone not related to an LED light company tell me the payback time of these LED lights?
Many thanks!


I’ll try and take up that one; I don’t work for an LED company! Let’s make this one difficult for the LEDs while we’re at it; don’t want to be accused of swaying the figures like an advertiser!

Firstly, I think your prices are a little harsh with the LEDs a (ours were £10) and £1 for a GU10 50W a little cheap, but i’ll use your figures anyway (you may buy in bulk).

50,000 hours for an LED is also going some. So let’s call it 20,000 in the real on/off world. And 1000 hours is half of the length of hours that I saw advertised on the Halogens I used to buy, even though they never used to last a year, but I’ll use 2000 hours to make it a challenge (let’s see who still complains!)

Right off the bat the LEDs last 10 times longer than the ‘equivalent’ Halogens, leaving you with £4 to find before making a saving on by buying a £14 LED.

Then at 12p per KWh of leccy over 20000 hours you get:
LED – 20000h x 7W = 140KWh x 12p = £16.80 over it’s life.
Halogen – 20000 x 50W = 1000KWh x 12p = £120 over 10 lives…


And how many of these horrible things did you say you had!?

Now the biggest hassle for LEDs is that you can’t easily dim them, but at a cost of about £40 a light with the correct fitting, you can, and with a good wide beam, 2700K Warm White none flicker LEDs, fitted by a professional, and doing your bit for the environment withought sacrificing style.

Win, win, win!


Come on Tytlas, enter the real world of the bog standard user. All they want is a decent light at the cost of pence………not £s, and cost effective, statistical analysis.


OK – buy a £14 LED 7W GU10 and it’ll save you £100 over it’s life, at least.

How’s that?