Usage cost of GU10 Bulbs

Apreciar

I have 28 GU10 50w bulbs that I am considering changing to LED, I want to compare the usage cost. Is the following calculation correct,

Wat x1000 x cost per kw. X hours usage. X number of bulbs

Mys cost per kw is 12pence

27col

It's easier than you think. If the LED's are 5watt then the cost will be 1/10th of what the existing 50w lamps are costing.to run. If the LED's are 3 watt the they are only costing less than 6/100 of what the existing lamps are costing to run.

Apreciar

27col wrote: »

It's easier than you think. If the LED's are 5watt then the cost will be 1/10th of what the existing 50w lamps are costing.to run. If the LED's are 3 watt the they are only costing less than 6/100 of what the existing lamps are costing to run.

Appreciate that but a a tenth of what, is the math correct.

anotherbaldrick

Apreciar wrote: »

I have 28 GU10 50w bulbs that I am considering changing to LED, I want to compare the usage cost. Is the following calculation correct,

Wat x1000 x cost per kw. X hours usage. X number of bulbs

Mys cost per kw is 12pence

No.
bulb wattage x no of bulbs x hours usage

---

X cost per Kw= cost of running
divided by 1000


ie. £1.34p if all bulbs are left on for 8 hours

Ectophile

Apreciar wrote: »

I have 28 GU10 50w bulbs that I am considering changing to LED, I want to compare the usage cost. Is the following calculation correct,

Wat x1000 x cost per kw. X hours usage. X number of bulbs

Mys cost per kw is 12pence

I think you've got a "times" where you need a "divide".

e.g. 4 lamps, 50W each, used 4 hours per day.
50 x 1000 x 12 x 4 x 4 = 9,600,000p (£96,000) per day :eek:

Instead try
(Watts / 1000) x cost per KWh x hours x no. of bulbs.
(50 / 1000) x 12 x 4 x 4 = 9.6p per day.

patriick

It's interesting to note that 1 watt used continuously for 24 hours a day, 365 days per year, at 12p per kwh, works out as £1.05 or approx £1 per year.

I use the formula of £1 per watt per year as an easy way of working out approximately what anything costs to run in my head.

i.e. 50w on 24 hours a day is £50 per year.
50w on 4 hours a day is 50/6 or £8.33 per year etc. etc.

paulmapp8306

Its the ammount of useage it takes to recoup the cost that matters when determining cost effectiveness..

A 50W Hal v a 5W LED = 44W difference. That savings using LED v Hal = 44(wattage difference)/1000(one Kw)x12 (pence) = 0.529pence per hour. One 5w LED (modern version) costs around £10 each, so the time taken to re-coup your outlay is 1000 (cost of bulb in pence)x0.529 (savings i npence per hour of use) = 1890 hours.

That "could" take 1890 days - 5 years 3 months- ish (if the bulb is in a bathroom only used an hour a day) OR is could take 236 days - 1/3 year ish (if the bulb is in a lounge used 8 hours per day).

the number of bulbs you have doesnt matter - because the time to recoup the outlay is the same per bulb. The more bulbs you have the more you save - but the more it costs you to but them in the first place.

Obviously if you have to replace the bulbs anyway, then its takes less time to recoup the extra cost, as you have to tak ethe cost of a replacement hal bulb away from the cost of the LED one to get the "extra" costs involved in going LED.

paulmapp8306

Oh - forgot. Long term its worth it (just replaced 20 myself), as the life of an LED bulb is around 50,000 hours (plently more than the 1900 or so to recoup the costs) and electric is only getting more expensive - so over time the "re-coup" period will be lower (though the longer you wait the cheaper the bulbs are likely to get).

paulmapp8306

Oh - obvious error lol. 50w-5w=45w not 44w difference. Fast typing doesnt equal accuracy lol.

You get the calculation though.