Understanding power, KWH and the price cap - a guide - with some analogies

[cakeorwine]

I know many people know this. But there are people who don't. I know that there have been threads before but they fall down the list. This is an anology for people.

Power and energy usage - think of power as how fast something goes and energy usage as the distance it goes

A joule is a unit of energy. So think of it as a mile.
1 watt of power is 1 joule per second - so 1 mile per second of energy.
The longer you go, the more energy you use - and that's what you pay for.

So a high power device - e.g. a 1000 watt kettle - it delivers 1000 joules of energy a second - so it's quite fast. But it doesn't travel very far as it's just used for a few minutes.

A low power device - e.g. a light - can be 10 watts - so 10 joules of energy a second. But it can be on for a long time - so it's going slowly but travelling far.

Price Cap

It can be misleading. It's not the most you will pay.

Think of it as buying carrots and potatoes. The price cap is the most you will pay for kilogram of carrots or potatoes

If you want to eat more carrots or potatoes, then you will pay more as you are eating more. But the cost per kilo of each vegetable is fixed

(there is also the standing charge which is a daily charge)

The energy companies decide how much carrots and potatoes they think you will 'eat' over the year and let you pay for that usage every month. If you look like you are eating more or less, then they will alter that monthly payment.

It's possible to 'fix' the price per kilo of carrots or potatoes for a year with some companies.

If you want to combine the analogies, some devices eat a lot of vegetables every second but may not eat for long. Some eat less vegetables every second but eat for a long time.

I think this would be a good animation.

I know many people get this - but some don't - so I hope it helps.

I understood it before I read this!

@Kezzie200 probably no need to comment then. Thanks for the explanation OP.

I think they might mean that they thought they understood it, then read this and it's confused them. I understand it, but I was a bit confused by mention of joules when I've only ever heard it talked about in watts (as in a 1000 watt hairdryer) and kilowatts (as in price per kilowatt hour). I read that bit a few times trying to make sense of it but couldn't quite get there so gave up. The potatoes and carrots analogy was good though, nice and simple and made sense.

^I've only ever heard it talked about in watts (as in a 1000 watt hairdryer*

Energy is measured in joules.

1 watt means that the device needs 1 joule of energy per second to work

So a 1000 watt device needs 1000 joules of energy per second to work.

If you want to do any job requiring energy, then you need a certain amount of joules to do this.

Ultimately, it's the joules that you are paying for.

As far as the potatoes and carrots analogy goes, my 'grocer' promised they could supply me with cheap potatoes and carrots for 2 years. They over promised.

@RichardMarxisinnocent ah right, yes you're probably right! My apologies then @Kezzie200

Basically - you can have a low power device but on for a long time which can use more energy than a high power device on for a short time.

People panic when they see a device go 'red' on the smart meter - but that's not an issue if it's on for a short time.

People don't see the devices that don't go red - but they should be aware of them as low power device on for a long time can cost a lot to run.

Like speed and distance