A guide to LED bulbs

A simple guide to LED bulbs, including prices, energy usage, GR10 vs MR16, heat dissipation, running costs and a whole lot more.

With energy companies about to hit UK residents with yet another price hike, you’re probably keen to find a way to make your bills more manageable. One option involves ditching thirsty halogen bulbs and replacing them with much more efficient LED bulbs. The problem is that buying the right ones can be confusing and you may be wondering if you will actually save any money.

With that in mind, License to Quill has decided to shed some light on the subject so you know your lumens from your colour temperatures and your watts from your beam angles as well as how long before you will reap the financial dividends of going LED.

Fitting type

Before buying anything, you should know what type of bulb you need in the first place. Like halogen bulbs, LED spotlights and LED bulbs have different fittings.

LED spotlights will have a two-pronged fitting that ends in either two sharp points or two flat circular ends. The former is pushed into two holes while the latter requires a push and a twist. LED bulbs will either have the twist screw or a bayonet.

Save yourself ordering the wrong bulbs by checking all fittings you will be replacing beforehand.

GU10 vs MR16

GU10 bulbs run on the 240v mains supply, which means you can swap use any GU10 bulb. An MR16 runs on 12v so it needs a transformer to step down a standard 240v UK mains supply.

The transformer for an MR16 is usually found within the light switch. Depending on the system inside (a magnetic coil or an electronic voltage system is most common), you may be able to get away with installing LED bulbs without any issue. However, you may see flickering.

Fitting MR16 LED bulbs may force you to purchase an additional LED driver to alleviate the flickering issue. Alternatively, you could go the route of purchasing the bulb and fitting, which would allow you to use the less annoying GU10 fitting. Either way, the initial cost will be greater but you could still save money.

LED bulb technical jargon

Colour temperature
Colour temperature is one of the most important aspects of a bulb because it governs the colour of the light. The lower the kelvin number, the warmer the light appears to the eye. The higher, the colder it looks. For comparison, the warm, yellowish light from a 50w halogen bulb is typically 2,900k.

Colour temperature preferences are subjective so it’s worth going to a shop to see a comparison. If you are unable to do that, play it safe with somewhere between 3,000k and 3,200k as this will give you a light with a good balance of warmth and whiteness.

If you crave perfect white, 4,000k is the colour you need. Beyond that, white will start to become blue, making the light feel cold and clinical.

CRI
CRI is short for colour rendering index. Higher is better, because this number governs how close a light colour is to a reference light source such as daylight or a halogen bulb. 0 is worst and 100 is best. For a good quality LED bulb, you should be getting somewhere between 70 and 90 CRI.

A good CRI is important because a high number means the colour temperature you are hoping for is likely to match the reference. For instance, a LED bulb with a score of 80 CRI that promises the colour of a halogen is matching 80 per cent of the visible colour spectrum of a halogen. 90 CRI would mean a 90 per cent match.

Beam angle
The average halogen bulb will have a beam angle. This is the angle at which it projects light. A common mistake is that LED bulbs with a similar angle will match a halogen. However, because halogens typically use a multifaceted reflector to reflect the light, the beam angle is going to be much wider than specified.

With an LED bulb, the angle on the box is going to be the angle you get so it’s important to think about this beforehand as they are less forgiving.

If you want a very focussed light, 25-degrees will suffice. If you want something similar to a halogen you should go for between 60 and 135-degrees. Bear in mind a tall ceiling will give a smaller angle LED bulb enough distance to spread so it would be less of an issue. On a 3-metre high ceiling at least 38-degrees is a good idea.

Lumens
Not to be confused with that strange Swedish cartoon The Moomins, lumens are a measurement of brightness. Because LED bulbs produce a much better quality light than halogens, the lumen number can be lower. To replace a standard 50w halogen, you want at least 400 lumens.

What is watt?
Like with standard bulbs, the higher the wattage the brighter the light you get. So, in theory, a 6w LED should produce a higher lumens number than a 4w, assuming the same bulb design and manufacturer.

Most electricians will use 3 to 4w, but depending on the volume of a room you may want to go to a 6w LED bulb. If a good quality vendor like Philips says a 4w is a like-for-like 50w Halogen replacement, it probably is.

Heat dissipation
Ever touched a light bulb that has been on for a while? Yeah, it gets seriously hot. All that heat is not only a waste of energy, it can affect the lifespan of a bulb.

Cheap bulbs typically use cheap materials that, way before their advertised lifespan, will fail to do their job and the LED will die, costing you money to replace. Even though you could buy ten cheap eBay LED bulbs, the cost to replace them as they go pop will soon add up (and their brightness and colour will probably be off). Best to get it right first time.

Lifespan and warranty
That brings us neatly onto the lifespan and warranty of a bulb. As you’ve probably guessed, the lifespan is how long a bulb should last. The warranty is how long a manufacturer will replace it if something goes wrong.

Basically a lengthy warranty from a reputable vendor is indicative of the faith it has in the product. Three years is a good figure to expect as that will see you well into the lifespan of a bulb.

On the subject of lifespan, these figures can be slighty dubious. Some cheap eBay products will tell you 50,000 hours, while a far better Philips alternative claims 35,000 hours. No prizes for guessing which vendor is being honest and realistic in its claims.

Although LED bulbs are more expensive than halogens, the latter usually only has a lifespan of 1,000 to 2,000 hours. So for every 35,000 hour LED bulb, you need 17.5 halogens.

Adjustable vs fixed
This is more a point about buying an LED fitting. Downlights typically come in fixed or adjustable forms. The former means the beam direction is fixed, the latter allows you to adjust the angle of the beam.

When is adjustable preferable?
Adjustable downlights are useful in sloping ceilings because you can tilt the angle to give you a downward light. A fixed downlight would point down at the angle of the ceiling. Adjustable has the added benefit of allowing you to focus on a specific part of a room such as your cooker or a glass cabinet, while a fixed fitting does not.

Dimmable
If you want the option of dimming your LED bulbs, you will need to buy LED bulbs that can be dimmed. This usually comes at a price so if you have plain-old light switches there is no need to pay extra unnecessarily. But if you do have a dimmer, make sure the bulbs you are buying can be dimmed or you will be disappointed.

Dimmer switch
LED bulbs operate at a different voltage to halogens so often a specific dimmer is required. Sadly, it’s very easy to dim an incandescent bulb but not a more efficient LED variant.

Ideally, you need enough watts from all your connected bulbs to meet the minimum requirement of a dimmer switch. If not, it may not work and/or you could see unsightly flickering. If your current dimmer is unsuitable, it will be worth finding something designed to cope with LED bulbs.

How much money can LED bulbs save?

LED bulb electricity cost
Because prices can fluctuate, let’s assume you choose to buy 10 Philips 4w Master GU10 LED bulbs. At £12 a bulb, that would set you back £120. 10 50w halogen bulbs would cost about £1.50 so that’s £15.

So far, not so good for the LED bulbs but let’s start factoring in the power gains. Ten 4w bulbs equals 40w, which as a kWh is 0.04kWh. Multiply that by three hours of use a day and you get 0.12kWh. Over the course of 365 days that equals 43.8kWh. Still with us?

Over a year those ten bulbs are, therefore, using 43.8kWh of electricity, which multiplied by an electricity rate of 12.5 pence equals £5.48 a year. This handy electricity cost calculator will do all the math for you.

Halogen bulb electricity cost
One day of use for the halogen bulbs would require 1,500w or 0.15kWh for three hours. Multiply that by 365 days a year and you get 547.5kWh. Throw in the kWh unit cost of 12.5p and the annual cost of running those ten halogen bulbs is – drum roll please – £68.44.

So how long is the payback time?

Glad you asked. The cost of the halogen bulbs and the annual electricity cost equals £83.44. For the LEDs, the cost is £125.48

Your energy bill may have a day rate you need to pay just to have electricity. Seeing as this is additional cost is added on top of the kWh pence rate, in both cases you would be paying slightly more than I’ve taken into account. Because the additional cost will be the same for both halogens and LEDs, the payback time is unaffected.

10 x 4w LED bulb payback time versus 10 x 50w halogens is about 9 to 10 months. So LEDs will start making up for their initial cost sooner than you thought – not too shabby, huh? Of course, if you have to change the whole fitting then you are looking at about a year, but that’s not a great deal of time in the grand scheme of things.

Bear in mind our crude math ignores the longevity of LED bulbs. Knowing LEDs can last hundreds of times longer than a halogen, the money saving could in fact be a few quid higher as the latter will need replacing more often.

So should I deck my house out with LED bulbs?

If you plan on staying in your home for the foreseeable future (even if not, you could take the bulbs and fittings with you) and can afford the initial outlay, LED bulbs will save you money in the relative short-term if you buy 10 to 20 bulbs.

For much larger houses with 50 bulbs or more, spending £500-odd just to swap to LEDs will be daunting and therefore payback time will be longer. At this point, it’s important to remain in your home for two years or so to reap the cost-saving benefits.

Conclusion

In recent times the price of LED bulbs has come down significantly while the brightness and quality has gone up to the point where they are now excellent replacements for halogens. As you’ve seen, by changing 10 bulbs you can start saving money in less than a year – giving you more money to spend on the fun stuff.

Ultimately, with energy prices about to soar, swapping to more efficient lighting and getting into a fixed rate tariff could save you some serious dough.

Let’s also not forget fossil fuels will run out at some point so there’s no harm in eking out what’s left. The eventual alternative is we end up with much less light than we’ve become accustomed to.