Confused about the price cap and energy consumption. Here's the thread for the physics and the maths to help you

[cakeorwine]

I've seen a lot of threads on here with people asking about their energy bills.

So a few basics here - and then I am sure people can add their own.

The price cap is an average expectation of what a household will pay. It's based on typical consumption and can vary between areas.

There is a daily standing charge and a cost per kilowatt hour.

There are figures available on typical energy consumption in a house.

According to Ofgem, the average household in the UK has 2.4 people living in it, and uses 2,900 kWh of electricity and 12,000 kWh of gas respectively. This works out as an average of 242 kWh of electricity, and 1,000 kWh of gas, per month

Electric devices have a power rating - in watts.
Devices that need a lot of power have a high power rating.

If you use a 1000 watt device for 1 hour, you have used 1 KWH of power (1000 watt hours)

That's 1 unit - about 28 pence with the new rating.

If you use the same 1000 watt device for 1/2 hour, that's 0.5 KWH - 0.5 units.

So if you use a 100 watt device for 10 hours, that's also 1 KWH (as it's low power but for a longer time)

Heaters are high users as they are on for a long time. As are immersion heaters.

Gas is different - you need to use a formula to change the volume of gas used from cubic metres into kilowatt hours.

A Smart meter will give you an indication of when there is a high energy demand, but don't forget that a low power device on for a long time will end up using a lot of energy.

So it's the kilowatt hours you need to look at whenever you question your bill.

How bad are standby appliances? I leave my radio/CD player on standby but almost never use it these days (like once every few months!); my printer is on but goes into standby-mode, so does the TV. I thought that standby wouldn't actually use too much power, as it's mostly just keeping a red light on and maybe a small amount of energy to power a battery to remember the clock and settings or something.

I have a few other things that are constantly plugged into chargers of some sort (e.g., an old phone, a philips Lumea device, cordless straighteners, cordless handheld vac, robotic hoover) so that they would be charged up if I needed to use them. I assumed that once they were fully charged, they would use very little energy keeping them topped up when plugged in, but actually that might not be true; if they discharge their batteries when not plugged in, that probably means they are constantly sucking small amounts of power. So maybe I just need to get better at deciding when/if I need to use those sorts of rarely-used appliances, and plug them in a few hours in advance.

I also have a few chargers plugged into the wall that aren't being used, but are just kind of stored there in those sockets ready to use if needed, but I read somewhere that even that could use some electricity (but I'm not quite sure how!).

I leave my desktop computer, monitor, modem, and router/back-up time capsule device on all day (and the modem and time capsule on permanently), which probably adds a fair bit - I know the modem and time capsule often feel a little warm, which must mean they are fairly energy intensive. I suppose I could turn them off at night along with the computer and monitor.

I don't have a power meter (yet) so don't really know if all of this is actually worth trying to change my habits - some of it would be easy enough to do (don't use the radio/CD, Lumea, old phone, etc enough for those to matter), but there is convenience in having the straighteners, landline phone, printer, ipad, handheld vac, robot hoover etc ready to use when I need them, and I'd give up the convenience for major power savings but not pennies a month!

Our gas and electric figures are very high. We live in a big old house with no double glazing (not allowed).
The gas units calculation is so complicated it hides the amount we’re using, but looking at our bills these are the figures for the last 12 months:
Electricity 7,300 kWh
Gas 52,000 kWh (no, not a typo!)

I’ll be buying one of those units for the electricity but the gas is more of an issue. Our meter is really hard to access and read which doesn’t help!

The gas bill numbers are so complicated, they should be more accessible.

I think that most devices on standby use very little power nowadays. My router uses very little power when actually in use.

Personally, I think it's the big gadgets that add up. Showers, heaters, pressure washers (2000 watts). They use a lot of energy as they demand a lot and are on for a long time.

Saying that - hair driers are about 2000 - 3000 watts. So every hour of hair drying costs 56p now. That can add up for a household.

Gas 52,000 kWh (no, not a typo

Wow!

Yes - gas is complicated. You need to work out the volume of gas you are using and then it gets converted into KWH .

You can use the following formula

Work out the volume used
Multiply by the volume correction factor (1.02264).
Multiply by calorific value (40.0).
Divide by kWh conversion factor (3.6).

That is a LOT of gas.

Also I think our gas company must be allowed to use a different sort of tarriff to pass costs on, as the rate for the past few months has been 8.5p per kWh, plus a standing charge, and that was significantly lower than the previous company which was 11p or something (plus a huge dailiy charge).

However, it's not just normal domestic gas supply, but some sort of distributed heating system in flats, so I guess they probably have different rules about what the unit price for gas is allowed to be. At least I hope there's a price cap. They're pretty crap about managing it all, and we don't seem to find out the tarriffs until they send us random bills at the end of each quarter! It's supposed to be eco-friendl(ier) than normal boiilers and maybe it is, but it didn't save any money with the old company anyway. The new company might have been OK if the initial rates carried on, but I'm sceptical that they will especially with energy costs rising generally.

What about the cordless devices constantly charging? I wonder if I'd save a lot by just charging them up as needed, but at the same time, it seems wasteful to let them gradually run down and then charge them up again fully before using (as well as inconvenient, and possibly - or possibly not, depending what you read - bad for the battery anyway!).

I have LED bulbs in all the lights, but I do tend to leave lights on all day, partly because I live alone and don't like coming back to a dark flat. But I should get better about just leaving one on (and not the spotlights in the kitchen/main room, which are the easiest to leave on but possibly more energy intensive!). I seem to use as much electricity in a small flat as I did in a larger cottage, but I guess much of it - fridge, oven, computer, lights, washer/dryer, chargers - is pretty much the same however many rooms, so I shouldn't be too surprised that my bills didn't come down much in a smaller place.

However, it's not just normal domestic gas supply, but some sort of distributed heating system in flats, so I guess they probably have different rules about what the unit price for gas is allowed to be

I have read about that - and the potential problems as you can't switch to your own deal.

www.theguardian.com/money/2022/jan/15/energy-bills-flat-dwellers-face-massive-rise-despite-price-cap

oh crap, I hadn't seen that. I assumed that there would still be a price cap!! The new company that we were switched to recently is certainly better than the first one, but it looks like that won't last.

I don't mind as much if they put the unit charge up, but it's the daily charge that really killed me before (70p a day!) because I can monitor my own usage, and the flats are well insulated and I can reduce showers and heating to not use as much gas. But I can't do anything about a daily charge, and it's the same for me in a small one-bed as for those in larger flats, which never seemed fair to me!

What about the cordless devices constantly charging? I wonder if I'd save a lot by just charging them up as needed, but at the same time

Now you're into the interesting current equations.

Interestingly - or not, when you charge something and there's an adaptor, you are stepping down the voltage. From 230v to 12v or 5v.

Not all the energy is transformed, so you get some wastage as heat. That's energy you're paying for going to heat up your room.

You would need to know how much charge your device took (again you can measure that), work out the cost of that, and then see how long that charge lasted.

But it's probably small fry as you wouldn't usually charge something up and let it run down completely.

Thanks for the calculation cake.
We obviously need to reduce our gas consumption considerably. Is there a minimum ‘healthy’ temperature that houses should be kept at?
I know that 18-22C is what most people aim for (we’re currently at the warmer end), but is it harmful to health to just put a jumper on and lower the thermostat to, say, 14C? And is there a way to calculate how many kWh that would save?

Well if it heats my room, then that might help

I suspect it's not worth the hassle of charging things up as needed, really. I doubt most of the things use all that much power. I suppose I might unplug things like the Lumea and old phone, as I could decide in advance about using them, and it would make little difference if I forgot. But I'm quite happy to have my ipad, straghteners, and robot hoover ready to go when I want them, so might be worth a little extra for those.

I suspect I'm really just playing at the edges though; it's the big things like the washer/dryer and lights that i have most control over. Fridge and cooker and microwave and coffee machine are just used as standard daily life and I'm not going to try to go into energy-saving habits to reduce their use really at this stage. (Though I haven't thought too much about the coffee machine actually; I turn it on and off and heat it up about 5 times a day and it is a bean-to-cup so does a lot of things, which might use more electricity than I think. But coffee is important....!)

It depends if you are vulnerable or not. Anyone with a chronic illness but especially those with lung conditions, old people and small children really need to be warm to stay in good shape. I think the minimum for those is 18c - but double check.

but is it harmful to health to just put a jumper on and lower the thermostat to, say, 14C? And is there a way to calculate how many kWh that would save

I think the best thing to do would be to try to do an experiment.

Try to get two similar days. Have 1 day with heating low and 1 day with heating at the temperature you like and see the gas you use.

Lots of variables to control though. They do say that turning your temperature down by 1 degrees will reduce your gas bill by 10%.

Some useful stuff here

www.which.co.uk/reviews/boilers/article/tips-to-reduce-your-heating-bills-aqik36F56DvJ

I suspect I'm really just playing at the edges though; it's the big things like the washer/dryer and lights that i have most control over

Lights are very efficient nowadays.

You are looking at about 10 watts per bulb - so it would take 100 hours of use and it would use 1 KWH. - 28p

But if you have a lot of bulbs like this, then 10 bulbs on for 10 hours would also be 28p.

I've ordered a heated shawl/blanket thing; it may or may not work (mixed reviews) but I thought I'd try it. I have a heated throw but it needs to be connected to mains all the time, which meant that it wasn't that helpful for what I needed as I have to move around in a small area, and I didn't end up turning down the heat much anyway. So this one has a power bank instead and I can move around with it - but it will take some experimenting to see if I do end up turning down the heat as a result, or if I just end up using more electricity to charge it up!

Opposite problem in the summer in that the flats are so over-heated and then I end up using a portable air conditioner and fan, just to get down to a survivable temperature. And I don't handle heat well, so it's pretty important for me. I know some of the professionally installed central air systems are much less energy intensive, but I doubt I'd be allowed to get it installed. I think I'll be spending a lot of time wandering around the nearby air-conditioned supermarket if it gets hot again this summer!!

This is a very interesting thread. Thanks cakeorwine

I have been monitoring our usage very closely as our monthly energy bill is just silly.

We are in a new, but small house that is very well insulated. I don’t have the stat high. The highest it would go to is between 18 and 19. I think our gas usage is well below average. It’s the electricity usage I’ve tried to investigate.

Over Christmas I was taking daily meter readings and was horrified by the usage Christmas Day and Boxing Day and the only thing I can put it down to is the electric oven which probably was on for longer than usual periods on those days. I can’t access the plug for the oven as it is integrated so can’t use a power checker.

Anyhoo I have banned use of the oven until I can afford to replace it and the electricity usage has gone down a bit. Using the slow cooker today for dinner 😊

Yes it's really interesting to get people to start questioning their energy use more specifically and not just make assumptions like turning lights off will make a notable difference.

I tried to find the rating of my coffee machine but couldn't find it on the manufacturer's website (i'ts probably in the manual somewhere when I find it!), but it says the efficiency rating is 'better than A', so at least given that I am going to use it, it's probably the best I can get. But it doesn't mean it might not be somewhere to cut down if needed.

I should time pre-heating the oven and see how long it really takes. I tend to just turn it on a while before I need it, but it could mean an extra 20 min or whatever that it's on; or if I forget to turn it off afterwards for 20-min, those things might add up.

I wonder if cafes and places like that will soon stop people using their power points for their laptops and chargers and things, especially if people start charging up whole power banks in them! Or if it's still a good enough business decision to give away free electricity in exchange for more coffees being bought. Maybe commercial rates have special deals.

This thread is so useful, thank you @cakeorwine . We are with Utility Warehouse and submit meter readings each month. Our bills are massively more expensive in winter (to be expected) but it’s primarily the electric which goes through the roof, but I’m not sure why? We have Gas Central Heating, all light bulbs are energy efficient and we are out at work all day anyway…we do use the tumble drier more often in winter (probably 4 times a week) but would that be enough to make an enormous difference? And we have aircon in the kitchen that we use quite a lot in the summer (it’s south facing with enormous windows and can get up to 40 degrees in the summer) but that doesn’t seem to cost much? It’s so confusing!!

I can’t access the plug for the oven as it is integrated so can’t use a power checker

If it's hard wired, then it has its own circuit and draws a lot of current.
Power checkers work up to 13 amps (so basically something you plug into a regular wall socket)

Vacuums are also power users - as they are reasonably powered and are used for a long time. A 1000 watt device will use 28p in 1 hour. That's what my Shark uses roughly.

Tumble driers.

Just an example

currysprod.a.bigcontent.io/v1/static/sp0099989_as_fiche-30277.pdf

Estimated 235 KWH per year based on 160 cycles.

So 235 * 0.28 /160 = 41 p per cycle. (based on the new price cap)

Air Con must also be expensive to run.

I agree air con must be expensive to run and we also have electric outdoor heaters than we use quite a lot in the summer when the nights get a bit chilly. But our electricity bill is SO MUCH lower in the summer, hence my confusion….

But our electricity bill is SO MUCH lower in the summer, hence my confusion

Have you got a daily spreadsheet of figures?

Or even hourly if you really want a project.

You should be able to see when your usage spikes and see what devices you have operating.

very interesting & helpful thread.
thank you @cakeorwine

comment on oven: we have an inefficient as shit smeg range cooker (came with the house) that has a wide oven. takes ages to heat up.
we have started to use the microwave more to pre-cook and the convectional part of the microqave oven to finish them off. we only use the big oven now for large amounts and batch cooking.
this seems to reduce the electricity we use for cooking but haven't tested it out with devices.

another question

boilj g water taps vs electric kettle vs kettle on gas hob?

what's most efficient to boil, say, one litre of water?