How to calculate

monkee · Oct 28, 2012

Hi please help i have gone looking for the calculation on watts per hour and the costs but it all seems a bit long winded,

lets keep it simple 60 watt lamp GLS left on for 8 hours are will billed in hours although we are using units also do we convert the lamp in to hours then how do i work out what i am being

charged

some helpfull tips would be great

ashrow · Oct 28, 2012

Your electricity supplier charges you in Kw per hour (ie 1000w)
So if you had 10 100w lamps on for 1 hour that would be that kw

monkee · Oct 28, 2012

HI so does my bill get rounded down say if i have used 2 hours and fiftheen minutes?

or do thay say 2.25 kw used is it 10 pence per kwatt used = £2.35

snowhead · Oct 28, 2012

60w lamp for 8 hrs= 480w

or in suppliers units 0.48kw

so say at £1 per kw (may be that sooon) = 48p

They'll charge to the nearest penny.

Knobhead · Oct 28, 2012

monkee said:
HI so does my bill get rounded down say if i have used 2 hours and fiftheen minutes?

or do thay say 2.25 kw used is it 10 pence per kwatt used = £2.35

KWHr is a measure of quantity not time. If you use 1 KWHr in 26 minuets, you will have used 2.3 KWHr in an hour.
Pity it isn’t as you think, I’d have everything on timers so they shut off a couple of minuets an hour.

martinh287 · Oct 28, 2012

So a 60w lamp uses 60w in one hour

ayjay · Oct 28, 2012

exactly
or for instance, a 1000 watt heater switched on for 1 hour uses 1kwh (1 kilo watt hour) if the electricity price is say-15 pence for 1kwh then the heater has cost you 15 pence for an hours use

ashrow · Oct 28, 2012

yes

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can i have electricity for 15 pence per Kw hour ? lol

martinh287 · Oct 28, 2012

And a 60w lamp running for 60min has cost the same as a 30w lamp running for 30min etc etc etc

nikmet · Oct 28, 2012

no......a 30w lamp would run for 2 hours

ashrow · Oct 28, 2012

i love the power of maths

Richard Burns · Oct 28, 2012

Take the wattage of the item: (W)
The time it is on in hours (or the minutes it is on divided by 60): (t)

(W/1000)*t = kWh

So for 60W lamp for 8 hours

(60/1000)*8 = 0.48kWh

100W lamp for 10min

(100/1000) * (10/60) =0.017kWh

2400W (2.4kW) oven for 1.5 hours

(2.4) *1.5 = 3.6kWh

once you have kWh multiply by your cost per unit (kWh) and get the cost of running that item for that time.

monkee · Oct 29, 2012

Richard thanks for the time to show us the calculation

to keep it simple lets say the cost 20p per unit used so the 2.4 kw cooker is on for 1.5 = 3.6

so 3.6 * .20 =0.72

£0.72

i tried 6watt @ 4 hours

(6/1000)*4=0.006

0.006*.20=0.0012

less than a peny your thoughts please

Richard Burns · Oct 29, 2012

monkee said:
Richard thanks for the time to show us the calculation

to keep it simple lets say the cost 20p per unit used so the 2.4 kw cooker is on for 1.5 = 3.6

so 3.6 * .20 =0.72

£0.72 correct

i tried 6watt @ 4 hours

(6/1000)*4= 0.006*4 = 0.024kWh

0.006*.20=0.0012
0.024* 0.20p = 0.048p

less than a penny your thoughts please

see changes above