Lighting is a difficult area to understand – there is a whole industry built around designing lighting layouts, however there are some basics that people should understand when looking into choosing lighting for their homes.
With incandescent lighting slowly being phased out in favour of low energy lights how should be choose the replacements.
Well there are two main alternatives:
Compact Fluorescent Lights (CFLs) and;
Light emitting Diodes (LEDs)
Both of these offer significant savings over incandescent bulbs, but the choice is made more difficult because of the following factors:
- Cost
- Energy used (measured in watts) vs light emitted (measured in Lumen or Candela)
- Lifespan (measured in hours)
- Colour of light (measured in Kelvin – cool white @ approx. 4000k, warm white @ approx. 3,000k and daylight @ approx. 5,500k)
- Quality of light (measured in Colour Rendering Index – CRI with 100% being all colours of spectrum)
- Quickness of response
- Materials used in manufacture (many people have been scared by the mercury involved in making CFLs)
Firstly to CFLs
1. Cost
CFLs are cheaper, but as with most things in life, you get what you pay for. So there is a quality issue. Higher priced bulbs tend to be better made, last longer, have better quality of light and are resilient to being switched off and on constantly.
2. Energy
I tend to work on a factor of 4. So a 15w CFL is equivalent to a 60w incandescent.
3. Lifespan
This varies with cost, but the figures quoted on boxes are when 50% of a batch has failed, so some will last longer than say 8,000 hours, others will not reach this milestone. Megaman bulbs tend to have the longest lifespan of around 15,000 hours.
4. Colour of light
CFLs come in all main colour temperatures.
5. Quality of light
Here CFLs don’t fare so well. There CRI tend to be around 70-75% so there are major areas of the colour spectrum that are missing and this leads to us seeing false colours that many people don’t like.
6. Quickness of response.
Again CFLs fail a bit here as they take some time to warm up. They work better at higher temperatures and so their brightness increases after about 30 seconds.
7. Materials used.
Most CFLs use liquid mercury to work. This has given the scaremongers a great opportunity to worry people, but it does take some fairly unique situations to be any danger whatsoever from lightbulbs. Megaman have gotten around this issue largely by using mercury in a solid state rather than a liquid one.
LEDs
1. Cost
This is the main issue at present with LEDs they are expensive. You can get really cheap 1w bulbs but they are really worthless if you are looking for light as opposed to dash of colour.
2. Energy
This is a more difficult area, but they are generally more efficient than CFLs with a factor of around 6 to 7. So a 6w LED will give around 36 – 42w of incandescent equivalent, but LEDs are directional and so one pointing up gives less useful light that one pointing down.
3. Lifespan
This varies with cost, but the figures quoted on boxes are when 50% of a batch has failed, so some will last longer than say the average of around 25,000 hours, others will not reach this milestone. Some will claim a lifespan of 50,000 hours, but this might be due to the temperature that they are tested at. The cooler the ambient temperature the longer they will last.
4. Colour of light
LEDs can come in all main colour temperatures.
5. Quality of light
This is where LEDs can excel (although not all). Many LEDs will have a CRI of over 90% so giving a wide spectrum of colour and hence giving a much more accurate quality of light.
6. Quickness of response.
LEDs are instantaneous and so again are ideal for areas where instant light is required.
7. Materials used.
LEDs require more electronics to work and so have more internal circuitry associated with them, but they do not contain mercury or any other poisonous materials.
So recommendations.
Personally I would use LEDs where you want:
Instant light
High quality light
Where changing bulbs is difficult / expensive
OR where you will have lights on for very long periods of time
Apart from that CFLs will suffice and give you adequate lighting.
