Amp-hours calculation

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Just following on from my thread yesterday about adding new exterior lights.....

I wanted to check that I have some load calculations correct.

If I have 2 lights each with 2 x G9 75W 230V bulbs in them the load would be

2 x 75 = 150 x 2 = 300 / 230 = 1.304 Amps

If I were to replace the G9 Halagon lamps with G9 LED's pulling only 5W 230V each would i be correct in saying that the load would be..

2 x 5 = 10 x 2 = 20 / 230 = 0.087 Amps

and as such replacing the G9 Halagons with G9 LED bulbs will drastically reduce both the load and the energy consumption
 
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Although the amp-hour is a measure of electric charge, and is usually used in reference to battery capacity :)
 
5W LEDs will not give as much light as 75W Halogens, though. Look as the output in Lumens, which is a measure of light output.

As a very rough and not very accurate guide, an old-fashioned 100W incandescent (filament) bulb gives about 1400 lumens. A 24W CFL about the same. This comparison is near enough to hold in your head.

People marketing novel lighting systems usually overstate the performance of their products, this also happened when CFLs first came out, so there are still older people who assert that energy-saving lamps are dim.
 
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And they seem to have the interesting property that when you turn them on they make the room darker, but if you stare into the beam they boil your eyeballs.
 
your electricity meter, and bill, use kWh, so it is quite convenient to calculate usage that way. You probably pay about 14p per kWh.

So if you had a house with ten 20W energy-saving lamps in use, you would be paying 2.8p per hour, which is trivial.

But if you were using old-fashioned 100W incandescent bulbs, it would be 14p per hour.

Your tumbledrier costs in the region of 42p per hour.
 
5W LEDs will not give as much light as 75W Halogens, though. Look as the output in Lumens, which is a measure of light output.

As a very rough and not very accurate guide, an old-fashioned 100W incandescent (filament) bulb gives about 1400 lumens. A 24W CFL about the same. This comparison is near enough to hold in your head.

People marketing novel lighting systems usually overstate the performance of their products, this also happened when CFLs first came out, so there are still older people who assert that energy-saving lamps are dim.

i've been looking at the light output and, going on stated values, the LED's seam to give out about half the Lumen Value of Halagons.
Im willing to give them a go though, im not looking for "flood" lighting and the bulbs sit inside a reflective casing.
 
Haha...Bang goes my attempt to get the corret termanology
Don't worry - it doesn't alter the comparison you were making. Electricity is sold in 'units' (of energy), which are kilowatt-hours (kWh). Your If you multiply your existing lights draw 1.304A, so, if they were on for, say, 100 hours that would be 130.4 amp-hours (130.4 x 100). If you multiply amp-hours by the voltage (230V), you will get approximately the amount of energy consumed (in watt-hours) in that 100 hours - i.e. 130.4 x 230 = 29992 watt-hours - and if you divide that by 1,000, you will get it in kilowatt-hours - namely 29.992 kWh, which we can call 30 kWh! At, say 15p per unit, that would cost you about £4.50 for the 100 hours. A similar calculation for the LEDs (drawing 0.087A) would give you a price of about 30p for 100 hours.

Having said all that, it's much simpler if you just work with the 'watts' and forget about converting them to amps! Just multiply watts by the number of hours to determine the number of watt-hours used during that time, then divide by 1,000 to get kWh.

Kind Regards,
 
But if you were using old-fashioned 100W incandescent bulbs, it would be 14p per hour.
Your tumbledrier costs in the region of 42p per hour.
But tumbledriers don't produce much light and are difficult to fix to the ceiling.

Stay with bulbs.:)
 
The idea was that lumen was how much light corrected for the human eye so it would not matter if tungsten, florescent or LED you could compare the light output to energy input so if you had for example 2 x 100W bulbs and you replaced it with 10 x 8W compact florescent before you ever flicked the switch you would know the 10 x 8W CFL's would be brighter.

Or if you swapped those 10 x 8W CFL for 10 x 1.8W LED it would be dimmer as 10 x 8W CFL = 350 lumen and 10 x 1.8W LED = 250 lumen.

However it all fails for many reasons I will list some.
1) With multi lamps it's not as simple as add the lumen for each lamp.
2) The way of measuring differs between first switch on and half hour after first switch one and only road transport have a set time delay after switch on.
3) Colour temperature should be auto corrected with lumen but it's not they got it all wrong.
4) Reflected light very much changes with type of light the high visibility jackets for example don't reflect sodium lamps very well.
5) Connected with 4 surface area of the bulb or diffuser.
6) Lamps becoming dimmer with age.

And as already said darn lies as to what both the light output and the lamp life.

So in real terms my 10 x 1.8W LED lamps give out far more light than all the rest in spite of having lowest lumen rating.

I was told it was just because the colour temperature was higher but looking at digital photos taken without flash it shows the aperture, exposure time and ISO of sensor so I can compare and the LED's are brighter.

I am sure there are cases where the reverse is true but the fact is we have no real way to compare lamps. It's just guess work.

As to power used the International unit is the Joule so 1 watt used for 1 second is 1 Joule so a 50W lamp used for 1 day = 4320kJ as you can see the numbers get rather large so we use the hour rather than second so there are 360 kJ = 1kWh the unit is rather crazy as energy has no time so the time in the watts cancels out the hours.

It's like saying I have two eyes per hour and 48 eyes per day / hours. It's really a crazy unit but seems we are stuck with it.

Energy is timeless if you lift 550 pounds one foot up it has energy only when you release that energy and allow it to return in say one second does it have power in that case one horse power.

So look on the side of a freezer it says something like 250 kWh/annum clearly the hour and annum cancel them selves out so there is no time. So it should say something like 90000 kJ.

The metric system it seems works by powers of 10 that's why there are 4.2j in a caloric and 980 kilos in a Newton it seems it's an easier number to work with than 32 and 16 although it would seem the computer world is returning to imperial with 32 pound in a slug etc.

Any wonder kids to day get confused as to what to call things?
 
...So look on the side of a freezer it says something like 250 kWh/annum clearly the hour and annum cancel them selves out so there is no time....

...Any wonder kids to day get confused as to what to call things?

you have certainly done your best there.

I find it quite easy to comprehend that an appliance might use 250kWh per year, and cost me £35 per year in electricity.
 
The idea was that lumen was how much light corrected for the human eye so it would not matter if tungsten, florescent or LED you could compare the light output to energy input so if you had for example 2 x 100W bulbs and you replaced it with 10 x 8W compact florescent before you ever flicked the switch you would know the 10 x 8W CFL's would be brighter.

Or if you swapped those 10 x 8W CFL for 10 x 1.8W LED it would be dimmer as 10 x 8W CFL = 350 lumen and 10 x 1.8W LED = 250 lumen.

However it all fails for many reasons I will list some.
1) With multi lamps it's not as simple as add the lumen for each lamp.
2) The way of measuring differs between first switch on and half hour after first switch one and only road transport have a set time delay after switch on.
3) Colour temperature should be auto corrected with lumen but it's not they got it all wrong.
4) Reflected light very much changes with type of light the high visibility jackets for example don't reflect sodium lamps very well.
5) Connected with 4 surface area of the bulb or diffuser.
6) Lamps becoming dimmer with age.

And as already said darn lies as to what both the light output and the lamp life.

So in real terms my 10 x 1.8W LED lamps give out far more light than all the rest in spite of having lowest lumen rating.

I was told it was just because the colour temperature was higher but looking at digital photos taken without flash it shows the aperture, exposure time and ISO of sensor so I can compare and the LED's are brighter.

I am sure there are cases where the reverse is true but the fact is we have no real way to compare lamps. It's just guess work.

As to power used the International unit is the Joule so 1 watt used for 1 second is 1 Joule so a 50W lamp used for 1 day = 4320kJ as you can see the numbers get rather large so we use the hour rather than second so there are 360 kJ = 1kWh the unit is rather crazy as energy has no time so the time in the watts cancels out the hours.

It's like saying I have two eyes per hour and 48 eyes per day / hours. It's really a crazy unit but seems we are stuck with it.

Energy is timeless if you lift 550 pounds one foot up it has energy only when you release that energy and allow it to return in say one second does it have power in that case one horse power.

So look on the side of a freezer it says something like 250 kWh/annum clearly the hour and annum cancel them selves out so there is no time. So it should say something like 90000 kJ.

The metric system it seems works by powers of 10 that's why there are 4.2j in a caloric and 980 kilos in a Newton it seems it's an easier number to work with than 32 and 16 although it would seem the computer world is returning to imperial with 32 pound in a slug etc.

Any wonder kids to day get confused as to what to call things?

Wow..Very details post, thanks very much, I think I understood most of it
Given what you have said, I might as well give LED's a shot and see how well they work.
Thanks
 

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