More on LEDs: some numbers

[Terry Fields]

Late last summer I went around the house replacing halogen lamps with LEDs, which resulted in such things as

430W of kitchen lighting being replaced with 32W of LEDs. At the same time in the hall and landing the total of 4 20W MR11 lamps were replaced with 4W LEDs. Many other lamps throughout the house were replaced.

Last month's electricity consumption was our lowest ever, at 192 kWh. However, it's not possible to put this down to any one cause, as SWMBO has taken to such things as making curry, etc, by the gallon and freezing the portions, saving on cooking time.

However, the usage of the hall and landing lights remains fairly constant; in winter (which lasted 4 months here this year) they are on 16 hours a day, and for the other 4 months they have been fitted, 5 hours a day.

4 months x 30 days x 16 hours x (4 x 20 - 4 x 4) = 123 kWh

4 months x 30 days x 5 hours x (4 x 20 - 4 x 4) = 38 kWh

Total 161 kWh of electricity saved @ 12.5 p/kWh = £20 saved.

However, in that 2500-hour period, probably most of the halogens would have blown at 2000 hour life, for a good-make lamp at £1:50 that's another £6 saved, for a total of £26.

That's nearly half the cost of the LEDs saved in 8 months. By the end of next winter the LEDs will have paid for themselves, and if the manufacturer's claims of a 25000-hour life are correct, still have another 20,000 hours of life left.

In 25,000 hours 1 x 4W LED will consume 100 kWh for a cost of £12:50. plus initial cost of the LED at £14:50, totalling £27:00

For 25,000 hours operation in one position 13 2000-hour-life halogens will be needed, at a cost of £20, plus energy consumption of 500 kWh or £62:50, for a total cost of £82:50.

Each LED over its life saves £82:50 - £27:00, or £55.50, and I have a total of 4 in this application, therefore saving £222:00 over the claimed LED lifetime.

[Dave Plowman (News)]

I can think of an easy way to reduce your energy usage. Called a switch.

[Terry Fields]

Would it be cheaper to fall down the stairs in the dark?

[Tim+]

Every house I've lived in has had a switch at the top and bottom of the stairs.

Tim

[RJH]

But there is comfort, security and convenience.

Although even I wouldn't go to the lengths of the OP - in my case it's a

2W undercounter kitchen LED array from Lidl, which is on most of the time. Hideous white light though - I will change it in the fullness of time.

[Terry Fields]

But you have to get to the switch in the dark...

Once upon a time I lived in a semi, where the party wall supported the staircases of the two properties. Before the kids were old enough to go out socially, it was click-click-click-bloody-click seventy times an evening. And this in a family that ran a 500W security light during the day and left all the house lights on at night. Sheesh...can't people see what's under their noses? Why didn't they just leave the landing light on?

As for the LEDs, it's a no-brainer on long-term cost, but they are more difficult to buy to to the greater range of choices, such as colour temp. It's no good saying 'it's hideously white' if you bought a 6000K lamp, or balme the LED.

[whisky-dave]

s, which resulted in such things as

e in the hall and landing the total of 4

e house were replaced.

How about factoring the cost of replacements.

; in winter (which lasted 4 months here

ve been fitted, 5 hours a day.

Now remmebring that one of the LEDs quoted it;'s life as 25 years for a nor mal amouint of use and 10 years if it were on for a few (3-4) hours per day . How long to you expect the whole LED unit to last ? Perhaps up to 4 years with 4 bulbs on average that'll be 1 change per year. This would significantly reduce your savings.

Of course what most people do is reduce their lighting in hallways. Before LEDs I went down from 100W to 40W then 25W.

I then discovered years ago a 1-2watt mains LED, that was very dim. But usable in hall lighting. Then I found I was leaving it on in bright day light. Now I use a 9W CFL I brought in a pound shop, they seem to last 1-2 years b eing on about 7 hours a day.

ve blown at 2000 hour life, for a

I have 10 35W halogens and since 2007, 2 have died. I mostly have them set to less than 50% quite often almost at minium I could do that with most LED s and I like to be able to change the brightenss according to what I'm doing.

next winter the LEDs will have paid for

providing you like the lighting effect of LED's I find them a little odd th e white ones although seem to be white give a monochrome effect to light. maybe these new ones are better, one of the tests I plan on making is takin g photographs so see how the colour quality and real brightness of the ligh t differs.

rect, still have another 20,000 hours of

20,000/16 = about 3.4 years provided their lifespan isn;t shortened due to being on longer than 4X their rated use.

lus initial cost of the LED at £14:50,

l be needed, at a cost of £20, plus

a total of 4 in this application, therefore

Claimed.

Did you see that consumer program last night about claimed MPG on varions c ars, nissan, ford, and others ?

[whisky-dave]

I ahve one of these in the bathroom

which means I don;t have to put on the light when goiong to the toilet day or night. But when having a bath there's 3X40W incandescent candles. I don't see the need for replacing them with LEDs.

[Dave Plowman (News)]

I have switches where needed. 5, for the ground floor hall. Lot cheaper than fitting low energy lamps and leaving them on just in case.

[Huge]

We have nightlights at the top and bottom of the stairs ...

[Dave Liquorice]

[Dave Liquorice]

Ah but I don't think you have a SWMBO'd and/or children living with you. I switch off far more lights in a day than I switch on...

[dave]

13 outlet in the bathroom. Is that a good idea?

[docholliday93]

That's been the case for me, too - unfortunately, though, whoever wired my current house (most likely the electrician I bought it from) didn't seem to believe in two way switching, so the two switches switch two different lights... In addition, the only switch for the hall light is 4 metres from the front door and round a corner, so the hall light tends to get left on near permanently.

[ARW]

It depends on how much you charge to fall down the stairs in the dark:-)

[Gefreiter Krueger]

Fit automatic lights. You can buy the sensors to directly replace lightswitches. The good ones need a neutral (or an earth will do if you don't have those pesky circuit breakers). But some are a lot better than others, get one with a relay in it as the transistor ones often require a decent load on them of about 60 watts, which doesn't happen with LEDs. This one is good:

[Gefreiter Krueger]

No such thing as hideously white. White is white, why settle for yellow?

[Gefreiter Krueger]

Of course, as long as he doesn't spray the shower at it for some reason. You have 13 outlets in the kitchen don't you? There's loads of water there too.

[Gefreiter Krueger]

LEDs, which resulted in such things as

time in the hall and landing the total of 4

t the house were replaced.

tant; in winter (which lasted 4 months here

y have been fitted, 5 hours a day.

a normal amouint of use and 10 years if it were on for a few (3-4) hours= per day.

ars being on about 7 hours a day.

d have blown at 2000 hour life, for a

set to less than 50% quite often almost at minium I could do that with = most LEDs

of next winter the LEDs will have paid for

dd the white ones although seem to be white give a monochrome effect to = light.

taking photographs so see how the colour quality and real brightness of = the light differs.

correct, still have another 20,000 hours of

due to being on longer than 4X their rated use.

1. plus initial cost of the LED at =A314:50,

will be needed, at a cost of =A320, plus

have a total of 4 in this application, therefore

ons cars, nissan, ford, and others ?

My Golf is 15 years old and gets more mpg than it's supposed to.

-- =

A mistake is evidence that someone has tried to do something.

[Jim Hawkins]

My kitchen/office is illuminated by seven Philips 33W flourescents that each produce 2250 lumens of warm white (2700K) light.. When there are LEDs available that can match that level of illumination I will gladly invest in a set. But I'm not holding my breath.

Jim Hawkins