Electricity usage forensics

[nikki]

I'm suddenly getting hit with quarterly bills that are about the same sort of size as what my annual spend has been for the last few years.

Attic flat, electricity only, the mainly-used room heated by an oil radiator with arduino thermostat control, t'other room has it's oil radiator just on a very low setting to stop my stuff getting damp.

I had a smart meter fitted at the start of this month.

As a result of an epic phonecall to npower earlier today, we've established that:

a) very few of the visits by npower meter readers have resulted in an actual meter reading getting put in the system. (I've been aware of quite a high number of estimated bills, but without owning a ladder there wasn't a lot I could do about it.) Amended bills are coming through with some hefty amendments.

b) average daily usage (worked out over the spread of about a year) up until August last year was about 12 units per day.

c) From August last year that's gone up to about 25 units per day. (And I wasn't even in the country for all of September and a bit more!)

d) Old meter and new smart meter would seem to be in agreement with the higher daily consumption.

Edited to add e) Talking through what's in each room with the energy efficiency dept, the back of the envelope calculation came out as expecting my usage to be about 8 units a day, not including the heaters - which are definitely not on all day - or lighting. We didn't factor in my clock radio, but also I lied about how often I do the hoovering, so that probably evens out 

I'm struggling to think of any behavioural changes at this end that would result in the doubling of electricity usage, so now having to embark on trying to track down any rogue appliances.

Any tips?

[Kim]

My primary suspect would be the meter and/or nPower's random number generator billing system, obviously, but if you've eliminated that...

12kWh/day is a 500W average load.  That's a lot for you not to have noticed.


Some sort of water heating appliance providing a steady trickle of hot water?

Fridge/freezer?  Dicky thermostat or failure of door seal (though the latter would generally be accompanied by tell-tale icebergs, and it's unlikely to be more than about 100W).

Landlord, weed/bitcoin farmer or similar incompetent having connected some mystery load to your meter?

Erm...

No, I'm struggling to think of anything else, unless it's just Weather (or change in downstairs neighbour's heating habits) causing the heating load to increase.

Does your smart meter give you a realtime power display widget?  That should simplify tracking things down by going around switching things off...

[nikki]

My mum thinks one of the other flats is syphoning off my electrons!

Water heating appliances are the kettle and the shower. I haven't used the big uninsulated tank thing for many years as it's a) big and b) uninsulated.

Freezer's currently being defrosted. Meter would suggest a load of 0.086 kW.

The heaters are big hitters - as the real-time display all too clearly shows. Think I need to get a measure of what proportion of time they're on for.

[Mrs Pingu]

I agree with your mum!

[Canardly]

Is your meter in your property or are they grouped in a communal area? Check if an immersion heater left on. Below is average UK consumption by house type from a couple of years ago which would seem to support your observation.

https://www.cooperativeenergy.coop/news-and-views/what-is-the-average-energy-bill-in-the-uk/

[Paul H]

I'm in a two bedroom electric only top floor flat, two storage heaters on the lowest setting to stop it feeling damp, 2.5kw oil filled radiator for most of the heat, hot water from kettle and shower, fridge/freezer, cook every day, washing machine twice a week and heated clothes airer, no TV, PC and amp on all the time I'm at home.  Averaged over the year I use 9 units a day. The oil filled radiator is pretty economical if I'm going to be in all day, it's stupidly expensive to run for an hour then go out.  I don't think I could use 25 units a day all year, I'd need all the heating on full and the windows open.
Are you sure they're just charging you usage and not reclaiming previous underpayment?  In the days of 50p meters, I was paying off a previous tenants arrears, it went on for 9 months, me telling them something was wrong, them insisting there wasn't.  You might also check that when they changed meters you stayed on the same tariff, I know the night rate I'm on isn't available to new customers, but I keep it even if my meter is changed.

[nikki]

I agree with your mum!

*gets out security marker pen*

Is your meter in your property or are they grouped in a communal area? Check if an immersion heater left on. Below is average UK consumption by house type from a couple of years ago which would seem to support your observation.

https://www.cooperativeenergy.coop/news-and-views/what-is-the-average-energy-bill-in-the-uk/

The meters are in a communal area. I don't use the immersion heater, and my annual spend for the last 3 years has been about £700 +/- £50  - so about right compared to those national figures.

I don't think I could use 25 units a day all year, I'd need all the heating on full and the windows open.
Are you sure they're just charging you usage and not reclaiming previous underpayment?

I know, right! Single occupant 1 bedroom flat: I think I'd notice a behavioural change that doubled usage. It's not even like I bought that robot exoskeleton I wanted...

There's some jiggery pokery as they amend some estimated bills, but the units things are based off of actual meter readings and the number of days between readings. I've been in this flat for getting on for a decade, so can rule out previous tenants.

[Pickled Onion]

Are you saying the only way you can read the meter is with a ladder? Can you borrow one for a couple of weeks? The way to get to the bottom of this is with some actual readings from the meter.

[Polar Bear]

Mirror on a stick or mobile on a selfie stick for reading the meter perhaps?

[Polar Bear]

Can't help but think that your numbers are unusually high unless you are doing something exceptional.  We use on average about 5kw of leccy a day though we do heat and cook by gas.  I reckon that our combined gas and electricity is less than your electricity and we have a two bedroomed* Victorian terrace.

*  Used to be three bedrooms but we converted the room over the kitchen into a large bathroom and gained extra space for the kitchen where the old bathroom used to be at the back of the house.

[nikki]

Ah-hah!
Remembered I'd once used a camera in video mode atop a fully extended tripod to investigate something in the loft...

634 kWh, up from 595 when it got pinged for a value about 30 hours ago.

The monitor box in my flat is saying £118 since the 8th of March. I know we've had some cold spells, but FFS, that's approaching what I'd expect a non-winter quarterly bill to be! 

I'm going to be out for a few hours tomorrow morning, reckon I'll switch the flat off before I leave and see what the numbers say when I get back.

[nikki]

Landlord, weed/bitcoin farmer or similar incompetent having connected some mystery load to your meter?

*Check's the Orrery is disconnected* 

[Basil]

I had a similar problem when we moved into this house.  I would take a reading at the same time every day and switch something off for the next 24 hours until I identified the culprit.

[Pickled Onion]

That's over a kW, constantly. If anything in your flat was using that amount of electricity it would be pretty warm in there. It has to be either a meter fault or the electricity is being used somewhere else. It will be interesting to see what the readings are after your experiment tomorrow, though if it's intermittent you might not catch it.

[nikki]

It's chugging along at ~0.45 kWh now with (I think) both fridge and freezer, laptop and phone chargers, one best-Birmingham-Landlord chandelier light fitting 3 candle bulbs), a clock radio, an arduino, NAS, router and a handful of 4-way block indicator LEDs on.

Heaters seem to be in the right 2 kW region, and microwave, oven and kettle are drawers of heavy loads, but equally I've seen the monitor at 0.0n kWh at other times of day.


My limiting factor at the moment for switching the flat off (at the mains switches on the fuse boxes) is the 4 (cooked) chicken breasts in the fridge. I defrosted the freezer last night so that's empty of food and I'm assuming the stuff that went into the fridge ice box is probably already wasted. (Off the menu anyway with FODMAP diet shenanigans.) The internet reckons fridges in good working order can keep food safely cool for about 4 hours without power.

In preparation I've put an assortment of bottles and ice packs in the freezer to ice up and use as ballast. Also turned the fridge up a couple of notches.

I *could* switch off overnight, risk/forego the chicken etc etc... Not sure if it'd be better to wait until morning though to increase the chance of someone else's activity influencing things?


Basil, what did your culprit turn out to be?

[andytheflyer]

Not sure this helps you, but, our 4 bed semi, with only the wife and myself, draws about 0.2kW in the daytime, little or no lighting, only fridge, freezer, gas-fired condensing HW/CH boiler, and 2 or 3 laptop computers running, plus TV and radios etc. on standby. That increases to about 0.5kW at night when there will be a few (mostly LED) lights on, plus the TV and the CH boiler actually running.

Cooking etc. bumps it up enormously (obviously) - but I gave you the base load for comparison purposes.  If my house was eating 0.45kW in what I'd call baseload, I'd be having a close look at what was actually drawing what.

[Basil]

Basil, what did your culprit turn out to be?

A night storage heater.   Inherited with the house along with the dual tariff.  The timer was buggered, which meant that it was drawing power all day during the high tariff day time rate.

Took it out, got leckie company to replace the meter with a single rate jobbie and negotiated a more sensible tariff..

[Kim]

I've got a blinky light on my electricity meter and RRDTool graphs...

We've got about 250W of baseload, most of which is computer equipment, alerting system, etc.  The fridge/freezer adds about 60-70W when it's running, at what I currently eyeball at about a 30% duty cycle (varies a lot with fridge contents and ambient temperature).  There's about 50W of that I can't readily explain by back-of-the-envelope calculations of things that are using power to do something useful so I need to do some proper experiments to see if there's a standby power hog somewhere (I'm betting microwave or oven).

The desktop PCs add another 120Wish each.  Boiler adds an inconsistent <100W or so when it's firing.  Room lighting is down in the noise.  Cooking, electric heating (when it's cold we tend to use a fan heater in one room rather than heating the whole house) and the washing machine add loads, obviously (I remain unconvinced by the merits of cold-only fill).  On the odd occasion someone uses the pissy landlord electric shower, it makes a huge spike that re-scales the graph and you lose low-level detail.  It's really easy to track barakta's tea consumption. 

[Quisling]

Cooking, electric heating (when it's cold we tend to use a fan heater in one room rather than heating the whole house) and the washing machine add loads, obviously (I remain unconvinced by the merits of cold-only fill).

OT but hot-fill appliances are great if you have a secondary return on your domestic hot water circuit so that the appliance immediately fills with hot. Ideal therefore in commercial situations or apartment blocks with central DHW provision.   However, as in our kitchen, you probably run off several litres of water before the hot tap starts flowing anything beyond luke warm - so even if you have a hot fill washing machine the chances are that it'll still fill itself up with effectively cold water.

[Quisling]

Meters rarely read incorrectly but can be crap.  Unfortunately, if you insist on a check and it's fine you'll get charged £100+ for the call out.  You can hire a calibrated logger for a week for around £150.

Immersion heaters can fail into the "on" condition, as well as fail to provide heat, which can sometimes be the problem but I note you mention you don't use an immersion.   If there's one there is it definitely switched off and not heating?  Can it be unplugged or is it hard wired?

If you predominantly use electricity for space heating and you have regular meter readings (ideally daily across a year but circa monthly can work reasonably well if) you can undertake a regression analysis to determine the correlation between energy use and heating degree days.  The resultant graph will show up any outliers where the usage doesn't readily correspond with the average kWh/degree day.

[nikki]

Okay, I switched off the flat this morning between 9:30 and about 2:30. Have also been periodically peering at the monitor box. I wasn't expecting this, but on the otherhand it does fit the problem rather nicely...

4:30 am (I'm a crap sleeper) the monitor briefly showed a usage from 08/03/2018 of £73.62. Seconds later it reverted back to £120.03. I was taking photos rather than writing down the figures, so I have proof I wasn't dreaming!

9:30 am, just before The Big Switch Off, it showed £74.47 and £120.89, bouncing between the two several times. Also photographed.

2:25 pm, just after switching everything back on again, it showed £74.47 and £120.89 again. No bouncing this time though.

Sooooooo, no power leechers this morning, but WTF with the meter readings?!
Possibly just an artefact of the power cycling?


Thanks for the extra info and numbers for comparison, folks.
Quisling: there's an immersion heater, but I keep it switched off at the wall except for maybe once or twice a year when it might get 30 mins or so of use.

I checked it yesterday: switch is off and the water's definitely cold.

[Cudzoziemiec]

Did you check the meter readings while everything was switched off as well? Just in case...

[mrcharly-YHT]

Did you check the meter readings while everything was switched off as well? Just in case...

She had everything off between 9:30am and 2:25pm

[Cudzoziemiec]

Exactly! If someone is syphoning off electrons.. Perhaps it could also give a clue as to the weird erratic meter?

[nikki]

Did you check the meter readings while everything was switched off as well? Just in case...

Only off the monitor box - had to get to a physio appointment and wasn't organised enough to do cameras on sticks too.

Have just spent 40 minutes on the phone to npower with them not addressing the very specific question ("What might cause the monitor to give two very different billing totals?")

They're now going to automatically get meter readings at 30 minute intervals, and I'm to collect 5 days' worth of daily meter readings - with and without heating on - to compare and contrast with their numbers. Presumably this will just then result in the Energy Wise team telling me I could spend less time in the shower, rather than addressing the problem in hand.

After reminding them of the original question, I'm to wait up to a month (£150 at this rate) for someone from the tech team to call me...


Their mental gymnastics really is very impressive: they can marvel at how one person's daily usage can suddenly go up by ~12 units a day, but they can't think in terms of asking "so what's changed?", only describing the current situation.


*bangs head against wall*