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The price of power

No, this isn't going to be a rant about the blatant Tory corruption where his Covid startup fund sent nearly £2 million to firms linked to his not-lacking-for-money wife; or how his "solution" to the recent by-election defeats appears to be to propose tax cuts for top earners.

Instead... it's quite literally about the price of power, that invisible (but increasingly expensive) entity that wiggles out of the end of a wire.

I've seen various red top newspaper articles with some rather shady maths in them telling you how much electricity you're using. So I thought I'd have a crack at it...

Your electricity bill, and various adverts, will tell you about the price of electricity. It'll tell you it's a mere 15p per kilowatt hour, or somesuch.
While that is technically correct, that isn't the price you'll be paying. My electricity, for example, is a flat rate of €0.1868/kWh (five centimes more than last year!). That means my 216 units came to €40,35. But then one must add the service charge (€26,46) and the service taxes (€4,68) and then the VAT on all of that (20% = €8,11 and 5.5% = €1,71).
The final result? €81,31.
Which is about twice what the headline "price per unit" is.

So the simplest way to get an idea of how much each unit of electricity is costing you is to take the price you paid and divide that by the number of units you used. This will be on your electricity bill somewhere. For me, it's 0.37643 (etc), so let's call it €0,38 per unit.

All of my prices are given in euros and centimes as I live in France. However it's just a name, all you need to do if you're British is swap in the appropriate values, then it's pounds and pennies for you.


A cup of tea

If you're smart and only fill up the kettle as much as you need for a cup of tea (don't fill the kettle all the way up), then it ought to be done in about two minutes.
The average kettle is about 2kW, which means it'll consume two units in an hour. But heating in two minutes means you'll be able to make about thirty cups for an hour's worth of electricity. Divide that by two (as it is two kilowatt), gives us a value of fifteen. Take the price per unit and divide by fifteen...
And making yourself a cup of tea costs €0.025, so round this to three centimes per cup.
A sad irony is that with French tea prices, it's around €0,20 per tea bag! Which is why I buy proper Tetley in sacks of 1,100, which costs a much better €0,04 per bag.

...which reminds me, time to go put the kettle on. ☺


Making a cake in a mini oven

This will take about half an hour in an electric oven, however the oven won't be on all the time. How long it will be on depends a lot on the design of the oven and how well insulated it is, suffice to say that "being on half the time" seems about right (especially if you have a mini-oven). This means we'll have the oven running for a total of fifteen minutes.
Now since most cakes have two layers, we should double this for the second layer. Half an hour of heating.
Now we should add in preheat time. It isn't unreasonable to need at least ten to fifteen minutes to get the oven up to working temperature.
Now we're up to 45 minutes. A mini oven typically has two heating elements. One at the top, one at the bottom, and they're both 1kW each and typically they both need to be on.
So... forty five minutes at 2kW. We'll work out 45 minutes at 1kW because that's just dividing the unit by four and multiplying by three (for three quarters of an hour), then double it for the other kilowatt.
Which means it'll cost €0,57 to bake a cake in a mini oven.

If you have a regular electric oven, the timings are typically the same except you can do both layers of the cake at the same time, so it's thirty minutes of 2kW heat. Which equals a kilowatt, or €0,38.

As for Sunday Roast... I've found everything from fifty minutes to five hours (!), so let's just make it easy and say it'll be about unit for every half hour of cooking.


A jacket potato in a microwave

Mom's recipe was simple. Stab a potato a few times and pop it in the microwave for ten minutes. Turn it over, give it ten more minutes.

Now the problem here is that while your microwave will be rated something like 800W, that's talking about the output power - how much radio energy is being blasted into that poor spud.
The input power is going to be higher. The magnetron is not 100% efficient, so you'll be looking at maybe something in the range of 1.1kW in to get 800W out. Add to that the turntable and the light, and it'll typically add up to something like 1250W. Your microwave will have a rating plate on the back (or bottom) that will tell you its real power consumption.

This, we can calculate too. Divide the price of a unit by a thousand (so per watt), then multiply by the rating of the oven. This means it'll cost about €0,48 to run it for an hour. Since it was only twenty minutes, divide by three.
Which means making a baked jacket in the microwave will cost €0,16.


A jacket potato in a halogen cooker

When I do it, it's an hour on one side and an hour on the other. It's much slower than a microwave because you're heating by convection, but on the other hand it produces a far superior result.
As halogen ovens tend to be horribly lacking in insulation (it's just a thick glass bowl), it isn't unusual to see that it'll be on for easily half the time. On the other hand, it's basically a fan and a bright floodlight (sort of). Which means your energy rating is going to be something in the order of 1300W.
Being rated a fraction more than the microwave, it'll cost €0,49 per hour to run. Two hours, of for half the time? Let's call it €0,50 for a jacket potato.

By way of comparison, doing the same in a regular oven will cost a fair bit more as that will be around 2000W plus preheat time. You'll notice I didn't bother to mention preheat as for a halogen oven it's something like four or five minutes, I just set it running from cold and factor that into the cooking time...which is basically "turn the knob as far as it'll go".


Chicken nuggets in an air fryer

About seven minutes of preheat time, plus about eight minutes of cooking time. My air fryer seems to do things like nuggets and fish fingers in about half the time it says for oven cooking, though it's all rather experimental as cooking instructions on packets rarely mention air fryers.

An air fryer is a little ring heater rated about a kilowatt, and a fairly beefy motor to keep that fan turning. With the proximity of the heat source, plus the fan, it is convective heating with attitude.
Typically consuming around 1500W, it'll consume a unit and a half per hour (or €0,57), but being so damn quick it'll only cost you around €0,14 to make nicely crispy nuggets. Or chips. Whatever.

Note: While an air fryer has a temperature control, in my experience if you leave it set at 200°C (which is the temperature most things want to be cooked at), it probably won't click off...especially if you take the panier out a few times to shake the contents.


Internet box

Also broadly counts for other similar rated things like printers on standby, mobile chargers, and so on.

Let's assume eight watts. Actual consumption varies wildly, and any markings on the device itself are liable to refer to the DC input consumption, not the AC consumption of the power brick.

Eight watts means you can run it for 125 hours for a unit of electricity. That's five-and-a-fifth days. There are 8,760 hours in a year (we'll ignore leap years for simplicity) which means 8750÷125 gives us 70 units. Which means keeping the internet running will cost you around €26,60 per year.

Now multiply this for all the stuff you leave plugged in.
Go on, unplug that inkjet printer if you aren't using it. It doesn't have a switch on the front, it has a little press button just like the "paper feed" one. Which means that the internal controller is always running in order to respond to it.


Satellite TV

Because of the need to power the LNBs and some rather meaty computational stuff going on inside, your typical satellite TV receiver will be drawing something in the order of 20-25W.
If we assume 25W, that means 40h per unit, or 219 units per year. Which is €83,22 per year.

Note that in the case of receivers with integrated programme guide, putting the box into standby doesn't actually do much. The video output is blanked and the little LED turns red. However in order to keep the EPG up to date, deal with middle-of-the-night firmware updates and so on, the box is pretty much entirely active all the time. As long as you can tolerate the several minutes it takes the thing to start up and get programme updates, it would make much more sense to unplug it when it isn't in use. Here's a thought... if you use it for around six hours a day, that means there's eighteen hours when it isn't being used. Which means you're paying around €21 for watching satellite TV... and around €62 for nothing.


Water heater

This is the second most frightful one.

Two hundred litres, from cold. You're looking at four or five hours. At a typical rating of 2.2kW.
Which means €0,84 per hour, or €3,36 to €4,20 to heat it. If you bath even once a week, then you're going to be looking at around €200 per year just for bathing.

Alternatives exist, such as on-demand showers, or simply boiling a kettle or two of water, putting it in a bowl, and washing like they did in the 18th century...


Electric heating

For a two kilowatt space heater (bar heater, fan heater, whatever) the calculations are much the same as for the water heater.

However, rather than spending money to always heat a space, try heating it only when you need it. For other times, such as when you're in bed, an electric blanket will be much better as it'll heat you for a small amount of electricity.
Sleep in a sleeping bag. Put the electric blanket on top of that (the sleeping bag acts as a basic insulator in case there's anything wrong with the blanket) and then put a decent duvet on top of that.
Electric blankets typically draw around 30W, but if you do it as said above you'll find that heat level 1 or 2 (out of five or six) will be more than adequate, so it'll probably cost about as much per hour as an internet box.

Safety! Electric blankets are mains powered heaters that go in bed with you. So... don't leave them plugged in while you sleep. Always use on a circuit protected by an RCCB. Don't crank it up to maximum and leave it there. A few minutes at max to get it warmed and then flip down to minimum, you'll find that's more than enough when the blanket is covered by a duvet. If you put it to max and leave it there, you could suffer serious burns. It isn't wise to put the heated blanket under you (plus your back is less sensitive to heat so you might feel colder than you are). Multiply that by a million if you're a bed wetter. ☺ Don't use if you have circulation problems or nerve damage, as your concept of what is and isn't warm may be quite out of whack.


Fridge (simple fridge with cold box at the top)

This is the frightful one.

Extremely difficult to calculate. Most fridges have a simple mechanical temperature sensor inside, and this actually varies quite a lot depending on the ambient temperature.
However, as a broad approximation, they tend to run for about five minutes in fifteen, or about twenty minutes per hour, drawing around 300W. Which means about €0,11 per hour continuously, or about €0,04 in actual use. Over the course of a year, this could be €350ish.
Unfortunately, there isn't really an alternative unless you really like corned beef and the taste of UHT milk.



One final note - if you have a smart meter, do not pay by Direct Debit. It seems that the energy companies are still debiting for imaginary "estimated usage" which is unjustified (and should be illegal) considering that you have a meter telling them exactly how much you're using on a daily basis.
You can usually pay by plastic on either the company's app or their website. Okay, it's not automatic, but you'll be paying for exactly what you have used and not some plucked-out-of-their-arse figure that is absolutely guaranteed to be more than your actual consumption.


And... since it only costs three centimes in electricity, I think, after writing all of that, that a good strong cuppa is what is needed now.



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jgh, 23rd October 2023, 06:50
Subsuming the standing charge amount into the per-usage calculation only really works if your usage is fairly consistant. Over a 12-month period you can probably get close enough for government work, but things on the timescale of weeks or months will vary too much. Things like having the lights on for four hours in July vs 14 hours in January. 
jgh, 23rd October 2023, 07:01
Looking at my spreadheet (a spreadsheet? of course I have a spreadsheet!) I used 246 units of electricity between June 2022 and June 2023, 20.5 units per month over 365 days. With my current tarrif that's (365*47.18p + 246*31.43p)*1.05vat = £262 per year, divided by 246 units gives - EEK! - £1.06 per unit used! I think I'm more comfortable with 71p per day, which is closer to how you think of power usage. 
C Ferris, 23rd October 2023, 09:30
Interesting - JGH is doing well - more like 10units per day here. 
Freezers use a fair bit - on all the time. 
Some time ago someone used a small freezer as a fridge very economic. 
A insulated kettle - to keep the water hot. 
With the change of phone lines - you will have to pay for powering it - some turn there Internet off at night - so no incoming calls. 
I presume it will still be copper up to the Fiber connection - otherwise lots of road/field digging.
Rick, 23rd October 2023, 14:31
"Things like having the lights on for four hours in July vs 14 hours in January." 
Three light bulbs. 6W each. Can run them for fifty five and a half hours for a unit. 
Which is just under 14 days in the summer (4h/day) or just under four days in the winter (14h/day). 
Which means the month of June will cost two units for lighting, while the month of January would cost eight. You'll probably find VAT is considerably more than the lights would be costing... 
Now, heating, if you're one of those people who heats entire rooms and wants it to be in the mid 20s, them you'll be looking at a big difference. 
That being said, I think including the standing charge is worthy as it can make up a notable part of the bill (and by using the bill amount, it also includes taxes). 
"20.5 units per month over 365 days" 
Eh? Do you have solar offsetting some of your consumption? 20 surely isn't enough for fridge, internet, computers, etc? 
My billing period is two monthly, so I use about 100 units a month. 
What? Per unit? Bloody hell! 
"some turn there Internet off at night - so no incoming calls" 
Which would make them both efficient and wise. ;) 
"I presume it will still be copper up to the Fiber connection - otherwise lots of road/field digging" 
If they're doing it properly and not a half-arsed job, it will be a full rip. 
I've mentioned a while back that the phone pole by the property boundary has a spool of fibre attached to it. Well, some day they'll tear out the copper and wire me directly to fibre. Then it'll be pulses of light rather than wiggling electrons giving me my Netflix. And, maybe, the security camera will be able to work in HD mode... 
The telco can recoup some of the cost by flogging off the old wires for copper recovery.
C Ferris, 23rd October 2023, 21:38
This change in landline by BT was I think what Labour talking about everyone going online.
VinceH, 24th October 2023, 06:19
"JGH is doing well" 
Astoundingly so, IMO! 
Why astounding? Well, I thought I was a low user at, typically, four units of electricity per day. 
Of which, my ancient & very large fridge freezer can be blamed for one per day (I know its useage because when I'm away from home it's the only thing left running, making it easily measurable). Over the course of a year, that's obviously 365 units. 
Although it's big (200cm high, with a 60:40 fridge:freezer ratio) I find the freezer space inadequate, so I've been thinking about an additional freezer, and therefore (on and off) looking at options. Originally, just something to go alongside the existing one, then that *and* a replacement fridge/freezer as well - which for a number of reasons is probably the way I'll go. 
But in all that occasional looking, one thing I've noticed is that my existing unit uses notably more electricity than something more modern. It obviously varies from one to another, with size being a factor as well, but a fairly typical figure for a fairly average fridge freezer is circa 200 units/year. 
So based on that, JGH's annual useage is just a fairly average modern fridge/freezer and nothing else. (Of course he could be using nothing more than a small fridge - I haven't looked at that sort of thing, but would expect them to be notably lower). 
As for calculating your bill to work out the cost per unit incorporating the daily/standing charge... I think that's an odd way to do it. For one thing, if your useage isn't regular it's only meaningful retrospectively; it means it's harder to predict your bills by reading the meter - for example if your last bill worked out as £x/unit last time, but this time you've used half as much, you'll under estimate this bill. 
Secondly: stupid people. "Hey, want to pay less for your leccy? Just use more, and it'll work out less per unit... 20% more used will knock a sixth off the cost you pay for each unit..." (Don't let the current UK govt. hear that - they think the public are as stupid as its lowest common denominators and might see it as a suggestion or idea to 'simplify' bills and make it sound like a discounting system!) 
Like JGH, I have a spreadsheet. I read the meter when I specifically need to submit for billing, and occasionally between that, depending on 'reasons'. I pop the date and reading in, and it calculates the total cost since the last reading (i.e. the line above), and also the daily average. 
And from that, I can see exactly what my bill will be. *Exactly*[1] If I use notably more or less than usual, it's still bang on the money. 
[1] Well until now. My cheap fix finished at the end of last month and I haven't double checked the new (cap) numbers and updated it. 🤷‍♂️ 
jgh, 24th October 2023, 08:18
I don't have a freezer, and my fridge doesn't have a freezer box. On top of that there's the timer on the central heating, and the server. The lights, computer, microwave and kettle consume power when I turn them on, such as the last six hours of watching Season 15 of Dr Who. :) 
I used 132 "units" of gas over the same period, which I think on my meter is cubic yards. An online calculator tells me that's 1424kWhr. My gas bill tells me it's (1424*9.75p+365*27.12p)*1.05vat = £250 per year, or 17p per unit or 68p per day. 
jgh, 24th October 2023, 08:24
It's very noticable that I'm using 7 times as much energy via gas than I am via electricity, but the per-day cost is near enough identical. And they want us to all go onto electric heating! I'd like to see them try to push eight times as much leccy down the cables under my street. Well, actually I wouldn't, I've seen what that results in in Hong Kong! 
VinceH, 24th October 2023, 17:21
Ah, just a fridge - thought that might be it. 
As I said, my monster uses one of my typical four per day. When I'm here there are things that I do leave permanently on - modem, router, PVR, etc - but they're all off when I'm away, and the PVR is brobably the biggest user out of those. ISTR deliberately leaving them on once to guage the overall daily cost, but I can't remember what it came to, so I'll just make up 0.5 units and leave it at that. 
So 2.5 units per day is me watching TV, using computers, cooking, etc. 
More of a problem for me is heating and hot water. It's a communal system, and I pay a fixed amount with my rent as a prepayment towards the bill for that. (IIRC it's currently around £13 or £14/week). 
Once per *year* I am billed for it, with the bill based on what the council have paid for the block apportioned to me according to what I've used. If my payments don't cover it, I have to pay the difference, and if I've paid too much I get a refund (or, as last year, it's held onto and put towards the next year). 
So although I can (and do) read the meters, until I get the bill I don't know what the actual *cost* is. 
The bill covers April to March. 
And in theory I get it in October. 😐 
In practice, the year before last IIRC it was November, and last year it was December. I expect it'll be December again this year. 
So until I get that I won't know what my heating bill was for April 2022 to March 2023, not whether I am in credit or owe any money. (I'm usually in credit, but obviously last year's prices... 🤷‍♂️) 
C Ferris, 24th October 2023, 18:41
I wonder if we be back to having a hand generator like the old phones - to cover for power cuts :-)
Rick, 24th October 2023, 18:49
I hope not Colin. D'you have any idea how much cranking would be required to get the thing through booting and associating with the network? 
Honestly, there are better ways to exercise the wrists. 😉

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