LED lighting

LED lighting FAQs

Rexel Energy Solutions frequently asked questions guide to LED lights and energy-saving LED light bulbs

What is LED Lighting?

An LED lamp is a light-emitting diode (LED) product that is assembled into a lamp (or light bulb) for use in lighting fixtures. LEDs are small, durable and need little power to operate. When compared with incandescent lighting LED’s are economically and environmentally the best choice.

Why LED Lighting?

With the rise in energy bills both commercial organisations and households can make significant savings and reduce their carbon footprint by replacing inefficient halogens and other bulbs with LED alternatives.

Why is everyone talking about LEDs?

The main reason is that they are the first really new light source in twenty years. Although LEDs were first commercially manufactured in the 1960s, it is only in the past 15 years that they have been used in commercial lighting applications. Before then, they were mainly used on indicator boards and signalling. Recently, high power LEDs have been developed, 1W and above, which means that they can produce useful quantities of light. LEDs are now found in every area of lighting applications.

Their advantage over conventional light sources is their long life, efficiency and small size. Being solid state electronic devices, they are also very suited to mass production techniques. Solid State Lighting, SSL, is another aspect of the spread of high volume, modern technology electronic products such as mobile phones, personal computers and TVs.

Can I save energy and money by changing to LEDs?

It all depends on your existing installation. The simplest way to find out is to ask the Rexel team for a lighting energy survey. They will tell you where you can save energy and provide a Return on Investment (ROI) spreadsheet showing costs and payback periods. They can also advise on retrofit lamps.

How do I choose a good quality LED?

The quality of LEDs and fittings varies enormously. As a rule, better quality LEDs will have longer life, higher light output, better colour rendering and lower energy consumption. Rexel staff are trained to advise clients on the quality of products available. There is often a choice of equipment available. Always read the data given in the literature carefully.

Is an LED down light more efficient than a compact fluorescent one?

Normally, the answer is YES but you must make sure that you achieve similar levels of illumination. LED fittings can be more glaring than CFL, but if the LED reflector is quite deep, you should be OK.

Some LED manufacturers make their luminaries with the same size ceiling cut-out opening as a CFL one, so you can simply replace the fittings on a one-for-one basis. If the down lights are for a corridor, consider the distance between the fittings.

LED down lights often give a narrower beam than its equivalent CFL, so you might get a less uniform appearance on the walls and floor.

What is the life of an LED driver?

Typically drivers are guaranteed for 50,000 operating hours. This is more than 12 years for most installations. Ask for the rated life. Compare this with the expected operating hours of your installation. Also check if there are limitations of use such as interior, exterior, ambient temperature, etc.

Are all LEDs Dimmable?

Many LEDs are dimmable but this will be marked on the product specification. It is always best to sample an LED to make sure it works well with your existing system before purchasing a large amount. 

How do I calculate how much a lamp costs to run in £ per year?

The calculation is: Watts x electrical cost per kWh x burning hours per year / 1000. For this, you need to know three things:

  • The wattage of the lamp (preferably including the gear losses if you know them, but just the lamp wattage will give you a good idea).
  • The cost of electricity per kW/hour. A kW/hour is often called a unit of electricity. A typical figure might be 12p per unit but remember that 12p is £0.12 when you enter the figure in your calculation.
  • The burning hours per year. A typical office is 3000 hours, dusk until dawn lighting is 4380 hours. As an example: 60W x £0.12 x 3,000 hrs / 1000 = £21.60
  • Note that occupancy sensors and dimming can also be used to save energy but it is harder to estimate actual energy savings compared with a simple ‘watts used’ calculation.
  • To achieve more accuracy in your calculation, you should include the control gear or driver losses. Wire-wound ballasts are being phased out and replaced by electronic ones. When considering LEDs, ask the manufacturer for the losses in the driver. Many LED retrofit lamps have an in-built driver. To make your comparison use the VA figure rather than the Watts value. For the technically minded, a good LED retrofit will have a power factor close to unity so the VA is almost the same as the wattage. Poor quality retrofits can have a pf close to 50%.

Can Rexel do the calculations for me?

Yes, our staff would be pleased to calculate the energy savings for you. Rexel have dedicated teams who will complete full ROI documents that will include energy saved and installation costs.

If I am offered a guarantee, what questions should I ask?

Firstly, the guarantee should cover complete failure of the luminaire within its rated life.
  • You should check what the rated life of the luminarie is.
  • Suppliers will normally pay a proportion of the replacement cost equal to the hours operated up to failure.
  • Ask if the guarantee covers failure of just some of the LEDs in the luminaire.
  • Luminaires with multiple LEDs should also be covered for the failure of some of the individual chips. This will lead to a reduction of light output or, in the case of RGB units, imperfect colour changing.
  • Also ask if the guarantee covers light loss over time.
  • Ask what the guarantee will cover if the output is less than stated.
  • Ask if the LEDs are on replaceable modules. This enables you to keep the luminaire and refit new, maybe more efficient, LEDs.
  • Look for conditions such as ambient temperature, switching frequency, change in colour appearance. The latter is particularly relevant with “budget” LEDs.