Energy saving - LED Lights

I've noticed that when many people refer to LED lighting in the domestic environment it's generally related to spotlighting and downlighting, either in the form of GU10 mains voltage or MR11 low voltage units, but LEDs have moved into the more mainstream domestic lighting sector over the last few years which is dominated in the UK by B22 bayonet cap light fittings.

We're pretty close to having all of our artificial light being provided by LED, the exceptions being a few of the low energy CFL (Compact Fluorescent Lights) in areas which are used so infrequently that expenditure purely to increase energy efficiency makes little sense. These bulbs are likely to be there for a while yet & when they finally fail, replacing units elsewhere with LEDs resulted in lots of spare CFLs in the cupboard.

The saving from moving to LED technology to provide the majority of domestic lighting is potentially huge, both to individual household domestic billing and to national power provision, so when looking into LED, what do we need to consider.

Setting Priorities

What lighting you choose to change over to LED and the order in which they're changed is a matter of return, affordability & priority so suit yourself and your own situation. Consideration must be given to the relative savings on energy bills which can be made and how quickly this returns the money paid for each bulb. Within the UK there's a general 'rule of thumb' which is useful to estimate the cost of electricity consumed by something like a lightbulb.

Rule of thumb: 1 watt of power consumed for 1 year costs approximately £1 if paying around 11.5p/kWh for electricity. Of course, this isn't accurate & changes in line with the tariff individual users actually pay, but for a quick rough assessment of running costs it proves extremely useful.

Using the above, a 60W bulb which is on all of the time costs around £60/year, so if it's on for an average of around 2.5Hrs over the year (10% of the day) the annual running cost is roughly £6. Replacing it with an LED equivalent delivering similar lighting levels using less than 10W would save around £5/year, which is pretty good if you're paying around £2/LED bulb, but not so good if the bulbs are £12 and/or they're used infrequently. Setting priorities is as simple as establishing which lights are used for the most hours, applying a cost to the energy they're using each year, ranking the results and working out which units you can't afford not to replace at a cost of £2 each immediately, then later use the ongoing savings to progressively replace units further down the priority list, eventually reaching a point where there's been a considerable cumulative saving for little up-front expenditure..

Light quality

Over the years I've come across many people, often elderly, who, having tried early generation CFL lights decided that either the 'light quality' or the time it took to 'warm-up' to deliver their rated light output wasn't what they wanted, it needed to be bright, clear & immediate. I must admit, the light quality of our early CFLs was poor so I fully understand what was meant, although later generation CFLs do provide vast improvements. Due to this ingrained memory of poor CFL lighting, many believe that LEDs react the same and therefore still stay clear of the technology, however, every LED unit I've come across is alost instantaneously on & delivering light, or off (although there is often a noticeable fade over a fraction of a second when switched off) and I find the light quality from most units we have to be similar to that provided by incandescent bulbs, so I'd certainly encourage anyone to at least try the technology out seeing that prices have fallen rapidly and therefore the potential for energy bill savings is huge.

What to look for

The majority of LED units available on the market fall into 'warm light' or 'cool light' categories. What is generally referred to as 'warm light' would have a yellowish hue which is more representative of incandescent lightbulbs, whilst 'cool light' would normally seem to be more intense, possibly with a blueish hue. The image below represents the illumination of a white surface by both cooler light (left) & warmer light (right) LED bulbs..

Effectively the type of light comes down to personal preference, but there seems to be a tendency to use 'warm light' in living areas and possibly using the whiter light (or a mixture of the two) in working areas such as the kitchen. Not all LEDs are categorised as 'warm' or 'cool', the colour often being described in terms of degrees Kelvin, or '°K' , where 'warm' would be around 2700°K and 'cool' somewhere around double that, so in the region of 5000°K.

Dimmable or not ?

To establish the answer to this is pretty straightforward considering that you can use dimmable LEDs in non dimmable circuits, but not the other way round, so the question to ask resolves to whether you already have dimmers and are they ever used. If you don't currently have dimmers on the current lighting circuits and are happy that the lights are either on, or off, then why pay a premium for dimmable bulbs. It could be argued that it would be a form of future-proofing the investment just in case, but considering that LED bulb prices continue to fall rapidly it may prove to be a relatively poor decision. We used to have dimmers years ago, but as they weren't used they were changed when replacing the old incandescents bulbs with CFLs.

Direct replacement

Replacing current lighting is really down to personal preference, however, if the current lighting conditions are broadly okay, then replacing what's already there with a direct equivalent is probably the most logical solution. Most LED lights specify their output in terms of lumens or equivalence wattage to incandescent bulbs. In general terms, whatever the wattage of an old incandescent lightbulb, a CFL unit of 25W would provide similar lighting levels and a LED equivalent would use in the region of 15W, much of this being dependent on make and quality. It's subjective, but my own experience is that as some designs of 10W B22 LED units deliver their light in the directions where it's more useful without creating noticeable directional 'pools of light', therefore offering an acceptable alternative to 100W incandescent bulbs. Where we have tried 100W equivalent (1521 lumen) LEDs, the lighting levels have proved to be a little too bright.

High CRI bulbs

High CRI (Colour Rendering Index) LED bulbs deliver a higher quality light which is capable of producing correct colours from artificially illuminated surfaces, however, whether there's a benefit at typical domestic illumination levels is questionable. A bayonet cap LED bulb in a standard sized room will deliver light which will be at sufficient levels to see by, but the illumination levels on average distance surfaces in the room will certainly not be anywhere near the bright daylight levels required to correctly distinguish colours and detail, so unless there's a requirement to provide indoor showroom or photographic studio lighting levels it's doubtful that there's a readily discernable difference between light provided by reasonable quality standard LED and premium priced high CRI bulbs.