MoneySavingExpert Chair, Martin Lewis · Editor, Marcus Herbert

# Help with how much my appliance costs?

• Posts: 9,936 Forumite
edited 1 December 2023 at 5:17PM
Can someone help with a couple of these?

I have something that consumes 0.05 kw a day.
I pay 0.27 per kwh.
Does this mean I am paying 13p a day or 1.3p a day?
If my "kw" you mean kWh, then at £0.27 / 27p per kWh, so £0.01.35, or 1.35p per day.

What are you trying to work out the usage of and where are you getting the data from? The problem is if you are looking at a device with a constant draw of 0.5kw, that means it will use 12kWh over the course of a day, which is £3.24 based on the 27p per kWh price.
So 0.05 power usage over 24 hours (that's the total use for 24 hours!) is £1.35?
I'm a bit confused as £0.01.35 is not £1.35
Krakkkers said:
Are you talking about something that consumes 50w continually or 50wh in a day?

If something had a constant draw of 0.05kW for 24 hours it would use 1.2kWh of energy over a day, which based on your 27p per kWh figure would cost £0.32.4.
If something had a constant draw of 0.05kW for 24 hours it would use 1.2kWh of energy over a day, which based on your 27p per kWh figure would cost 32.4p.
A quantity cannot have two decimal points !
• Posts: 82 Forumite
edited 1 December 2023 at 5:26PM
PeterGr said:
You have to calculate in kWh, which is kw rating for a length of time.

So if your appliance is rated at 0.05kW (50Watts), and it is used continuously for 24 hours,
The cost is 0.05 x 24 x 27 = 32.4p

Similarly, if the appliance is rated at 0.5kW (500W)
The cost is 0.5 x 24 x 27 = £3.24
I know it's confusing but no way is a set of LED Christmas tree lights consuming 32p of electric a day.
There is plenty of "way" for a set of LED lights running for 24 hours to use 32p of electricity.
I think the issue is with the data I have - it is displayed in kwh but shows the total for the day (well, since the plug was turned on, which I left on for 24 hours to get the 0.05 number).
Where are you getting your data from?
The app I have.
Posted a screenshot above.

Could you link to any LED Christmas tree lights (300 or less) that would use more than 32p a day based on a 0.27p per kwh charge?  Many websites suggest normal, typical installations (200-300 bulbs) would cost 2p a day, which would suggest my 1.3p a day is about right - and that calculation is on slightly more per kwh than what I pay and more bulbs.
• Posts: 1,124 Forumite
PeterGr said:
You have to calculate in kWh, which is kw rating for a length of time.

So if your appliance is rated at 0.05kW (50Watts), and it is used continuously for 24 hours,
The cost is 0.05 x 24 x 27 = 32.4p

Similarly, if the appliance is rated at 0.5kW (500W)
The cost is 0.5 x 24 x 27 = £3.24
I know it's confusing but no way is a set of LED Christmas tree lights consuming 32p of electric a day.
There is plenty of "way" for a set of LED lights running for 24 hours to use 32p of electricity.
I think the issue is with the data I have - it is displayed in kwh but shows the total for the day (well, since the plug was turned on, which I left on for 24 hours to get the 0.05 number).
Where are you getting your data from?
The app I have.
Posted a screenshot above.

Could you link to any LED Christmas tree lights (300 or less) that would use more than 32p a day based on a 0.27p per kwh charge?
You are doing it again, you pay 27p per kwh not 0.27p
• Posts: 1,338 Forumite
PeterGr said:
You have to calculate in kWh, which is kw rating for a length of time.

So if your appliance is rated at 0.05kW (50Watts), and it is used continuously for 24 hours,
The cost is 0.05 x 24 x 27 = 32.4p

Similarly, if the appliance is rated at 0.5kW (500W)
The cost is 0.5 x 24 x 27 = £3.24
Why is 0.05kW not 5W?  Or if you think it's 50W, why is it not shown as 0.50?

I know it's confusing but no way is a set of LED Christmas tree lights consuming 32p of electric a day.

I think the issue is with the data I have - it is displayed in kwh but shows the total for the day (well, since the plug was turned on, which I left on for 24 hours to get the 0.05 number).
OK, hang on here.  We're talking Christmas tree lights that are rated at 0.05KW, yes?
A KW is simply 1000 watts.  So 0.05 KW is 50 watts.  0.5 KW (half a kilowatt) would be 500 watts.  5 watts could be expressed as 0.005 KW.
Electricity is measured in Kilo-Watts - in a domestic situation - simply because it's a convenient multiple.  You could just as easily use Mega-Watts or even Giga-Watts (useful if you run a DeLorean !), but the average usage figures would just be a bit awkward for most folk to easily understand (everything would be rated as 0.000002 Giga-Watts or whatever).
So, your fairy lights pull 50 watts, or 0.05KW, whichever way you want to express it, it makes no difference.  So every hour they will consume 0.05 KWH.  If you use them for 12 hours constantly, that's 0.6 KWH, which is 16.2p.  Or 32.4p if you run them for 24 hours constantly.
The calculation is fairly simple.  Power Consumption (in KW) * Hours Run * Unit cost of leccy per KWH.
As I say, something like a fridge won't be consuming power all the time.  So it's plugged in for 24 hours but might only draw power for 16 hours.  So it's a little harder to accurately measure exactly how much it costs per day.  But something like a light bulb is easy to calculate, since it draws a fixed, constant current.

• Posts: 82 Forumite
Krakkkers said:

Could you link to any LED Christmas tree lights (300 or less) that would use more than 32p a day based on a 0.27p per kwh charge?
You are doing it again, you pay 27p per kwh not 0.27p
So why is it written with that decimal point where it is?
£0.27 is 27p.
£1.27 is one pound 27p surely?

As the poster above says, a number can't have two decimal points?
• Posts: 8,590 Forumite
PeterGr said:
You have to calculate in kWh, which is kw rating for a length of time.

So if your appliance is rated at 0.05kW (50Watts), and it is used continuously for 24 hours,
The cost is 0.05 x 24 x 27 = 32.4p

Similarly, if the appliance is rated at 0.5kW (500W)
The cost is 0.5 x 24 x 27 = £3.24
I know it's confusing but no way is a set of LED Christmas tree lights consuming 32p of electric a day.
There is plenty of "way" for a set of LED lights running for 24 hours to use 32p of electricity.
I think the issue is with the data I have - it is displayed in kwh but shows the total for the day (well, since the plug was turned on, which I left on for 24 hours to get the 0.05 number).
Where are you getting your data from?
The app I have.
Posted a screenshot above.

Could you link to any LED Christmas tree lights (300 or less) that would use more than 32p a day based on a 0.27p per kwh charge?  Many websites suggest normal, typical installations (200-300 bulbs) would cost 2p a day, which would suggest my 1.3p a day is about right - and that calculation is on slightly more per kwh than what I pay and more bulbs.
Loads on John Lewis seem to have power supplies rate at 7.2W or 9.4W, what their real world draw is I do not know. 7.2W for 24 hours is 172.8Wh, or 0.1728kWh, which is 4.67p. Larger sets of lights can use a lot more, especially external lights which are usually much brighter, most calculations for running costs will not be based on having them on 24 hours a day, so will typically quote a lower cost figure.

The initial confusion seems to be because you are confusing W, kW and kWh, your initial question was answered correctly. We have subsequently discovered that the question you asked was not the question you meant to ask because of the confusion of units, which now appears to be solved.
• Posts: 1,124 Forumite
0.27p is not £0.27
• Posts: 1,338 Forumite
edited 1 December 2023 at 6:06PM
Krakkkers said:

Could you link to any LED Christmas tree lights (300 or less) that would use more than 32p a day based on a 0.27p per kwh charge?
You are doing it again, you pay 27p per kwh not 0.27p
So why is it written with that decimal point where it is?
£0.27 is 27p.
£1.27 is one pound 27p surely?

As the poster above says, a number can't have two decimal points?
The decimal point is confusing you.  Actually, so is your original statement: "I pay 0.27 per kwh.".
0.27 "whats" per KWH?  0.27 pence, 0.27 pounds, 0.27 Polish Zlotys, 0.27 goats, 0.27 apples?
I suspect it's £0.27, or 27 pence.
You need to be careful with decimal points, and make sure you understand what you (and the electricity company) mean.
Don't get pounds confused with pence, and don't get watts confused with kilo-watts.  It doesn't matter how you express these quantities, just as long as you're clear what you mean.
You usage is calculated in kilo-watt-hours (rather than watt-hours, which would actually be perfectly valid), so it's simpler to use kilo-watts when you're looking at the power rating of appliances.  Your unit charge is expressed in "pounds per kilo-watt hour", so stick to pounds.  Just make sure you put the decimal place in the right place.
Would you prefer it if I gave you £34.27 as a gift, or would 3,427 pennies be better?  Of course it's the same thing.  If I offered you 34.27 pennies you might not be so chuffed
As a slight aside, you say "a number can't have two decimal points".  It can, just look at any petrol forecourt, petrol is 153.7 pence per litre or whatever.  So you can't actually buy exactly 1 litre of petrol, even though it's priced at so much per litre.  Always seems daft to me !

• Posts: 9,936 Forumite
HuCliveOfIndia said:
Krakkkers said:

Could you link to any LED Christmas tree lights (300 or less) that would use more than 32p a day based on a 0.27p per kwh charge?
You are doing it again, you pay 27p per kwh not 0.27p
So why is it written with that decimal point where it is?
£0.27 is 27p.
£1.27 is one pound 27p surely?

As the poster above says, a number can't have two decimal points?
As a slight aside, you say "a number can't have two decimal points".  It can, just look at any petrol forecourt, petrol is 153.7 pence per litre or whatever.  So you can't actually buy exactly 1 litre of petrol, even though it's priced at so much per litre.  Always seems daft to me !
Maybe I need to go to Specsavers: I can see only one decimal point in 153.7 pence. 🤓
• Posts: 478 Forumite
Here is a phot from the app:

This is a lamp with an LED bulb in it.
Today it has used 0.01 units of electric.

If I pay £0.27 per 1.00 units of electricity, then today it's used £0.27 (27p - surely not as it hasn't used 1.00kwh?) or £0.02 - 2p?
How long was this lamp on for on this day? If it was about 2 hours then you have a 5w lamp (0.005kw), and if it was on for just 12 minutes you have a 50w (0.05kw) lamp. This of course assumes the lamp is on constantly at full brightness. If your electric cost is 27p/kWh then the 0.01 units the lamp used is £0.0027 or 0.27p.

So the 5w lamp would cost £0.00135 (0.135p) per hour to run and the 50w lamp would be £0.0135 (1.35p).
Moo…

#### Categories

• All Categories
• 343K Banking & Borrowing
• 250K Reduce Debt & Boost Income
• 449.6K Spending & Discounts
• 235.1K Work, Benefits & Business
• 607.7K Mortgages, Homes & Bills
• 173K Life & Family
• 247.7K Travel & Transport
• 1.5M Hobbies & Leisure
• 15.9K Discuss & Feedback
• 15.1K Coronavirus Support Boards