LED vs Halogen

With the advent of smart meters and those energy-monitoring gadgets you get free from your electricity supplier it's much easier now to see which devices are costing you the most money.

Leaving your TV, hi-fi and other tech kit plugged in will cost you a surprisingly small amount of money per year. The latest devices must, by law, use 0.5W or less when in standby or 'off' modes, which means even a gadget-obsessed household won't run up a large bill by leaving them all plugged in and turned on.

I've been using an AlertMe system for several years to monitor power usage. Via the app, I can see at a glance how much power is being used at any given moment. It's easy to see by looking at spikes in the graphs when the cooker or hob was being used as they're the most power-hungry appliances we own.

One of the biggest surprises was seeing the staggering amount of power used by the low- and high-voltage halogen lighting which the previous owners of my house had installed practically everywhere.

All told they consume several kilowatts: halogen lamps are famous for being able to convert electricity into heat as well as light.

Naturally, some of those halogens are used more than others: the kitchen and lounge lights are turned on for hours on end in the winter. Replacing the bulbs with LEDs would have been a 10-minute job, but I held off for several reasons.

First, those early LED replacement lamps were an unknown quantity: would they actually last as long as manufacturers claimed? Would they offer the brightness and coverage of the existing halogens? Would they be compatible with the existing 12V transformers and be dimmable? Finally, how long would it take before I'd saved enough power to make my money back and start seeing a smaller electricity bill?

It's easy to work out what it will cost to replace your bulbs, but not so easy to calculate how much you'll save and how long before you break even.

A typical LED bulb costs anywhere from £5 to around £30, and you tend to get what you pay for in terms of the quality of the light as well as the actual brightness and coverage.

How to choose LED bulbs

When shopping, it's well worth sticking to well-known brands and avoiding no-name cheap deals. Bear in mind that an LED bulb has an electronic controller as well as the LEDs themselves. The electronics are more likely to fail than the LED, and given the cost of the bulbs, it's well worth comparing warranties and paying more for a longer warranty. Look at reviews, too. A deal offering 10 bulbs for the price of one top-tier lamp might sound tempting, but they're usually cheap for a reason. We've heard plenty of stories of cheap bulbs failing within days, and the manufacturer refusing to replace them despite a two-year warranty.

Colour temperature

There are other aspects to consider, of course. Colour temperature is crucial: most people prefer the warm white, which is very similar to halogen, rather than the 'cold' bluish tint of white or cool white LEDs. Look out for the actual colour temperature in Kelvin: 2700-3000K is a good warm white. Higher values will look cooler - lower numbers warmer. If you want a whiter look, be careful as you can end up with a very clinical look.


You also need to look at brightness, measured in lumens. Try to find out how many lumens your current halogen lamps produce, and match or exceed that. Some cheap bulbs produce as little as 120lm, but you'll probably find you need 350-400lm to provide the same light output as your existing bulbs.

Beam angle

Next up is beam angle. This determines the spread of light the bulb produces. A narrower angle means light will be concentrated on a smaller area, like a spotlight. A larger angle is better for lighting a larger area, but don't forget this means it could appear dimmer overall. For replacing Halogen downlights, look for a beam angle of around 40 degrees. Incadescent replacements should have a much larger beam angle, say 140 degrees.


CRI is another spec you should see (if you don't, it's worth asking for the CRI figure). Here's why: CRI stands for Colour Rendering Index and is a measure of the light quality from 0 to 100. In other words, the CRI score tells you if objects appear the correct colour when lit using that bulb. Incandescent bulbs had a brilliant CRI, but not so with fluorescent tubes. If you want to avoid bad-looking lighting, it's crucial to go for LEDs with a high CRI.

Existing equipment

There are no guarantees that low-voltage LEDs will work on your particular transformers or dimmer switch, so it's wise to buy from a retailer with a good returns policy. You can't simply buy one bulb to see if it works: many older transformers require a minimum load and replacing only one halogen won't tell you if the total wattage used by a full set of LED bulbs will be enough. If the draw is too low, they may flicker or not work at all. It can also cause premature bulb failure.

LED vs Halogen: Calculating savings

An LED bulb's specifications should tell you the halogen or incandescent equivalent. For example, an LED lamp equivalent to a 35W halogen might consume only 7W. You can multiply the wattage of your existing halogen lamps to work out your current power consumption, and then subtract the total power draw of replacement LED bulbs to see how much you'd save. In my case, replacing six MR16 (GU5.3) lamps in my kitchen would save me 168W, which is 80 percent less.

Of course, you also need to factor in how many hours per day the lights will be used in order to work out the yearly saving. There are many online calculators which will do the sums for you.

If I use my kitchen lights for eight hours per day every day, then I'll save almost £60 per year by switching to LEDs. However, the bulbs cost £20 each, so for the first year, it will actually cost £60 more. Only at the end of year two will I break even. Then, assuming that electricity costs remain the same (unlikely) I'll save £60 each year.

In reality, the average daily use across a full year is probably around three hours or less, meaning it will take even longer to make a profit. And, because LEDs use so much less power, I'll be inclined to use the lights more.

Verbatim provided me with six MR16 warm white dimmable LED bulbs to test for this article, and I was impressed at how much brighter they were than the 35W halogens I was replacing. Not only that, but there was no warm-up time: the lamps instantly produced their maximum brightness. Their beam angle was slightly narrower, but not noticeably so: the overall impression was that I'd replaced them all with even higher-power halogens, yet the power usage dropped from 210W to a shade over 40W.

LED vs Halogen

Clearly, LED bulbs have come of age and the average person won't be able to tell the difference in the quality of light if you replace your existing halogen or incandescent bulbs. It can be a considerable expense to start with, but you'll make savings in the long term - and you'll help the environment to boot.