How Much is this Costing Me?

[KWILParticipant @kwil]

You do not need a so called Smart meter to tell you to switch something off to save money. If you only turn on what you really need, that saves money.

[Max ToleranceParticipant @maxtolerance69251]

I have a full workshop in my cellar.I have lathes, mills, grinders, drills etc.etc. All my machines are three phase and I am fortunate to have a three phase supply so I don't need converters / inverters. The normal house hold electrics are of course single phase. I have most of the house on red (Brown) phase. The kitchen is on Yellow ( gray) phase and the only use of the Blue (Black) phase is my workshop. I also have three meters, one for each phase.

This makes it easy to see how much I typically use running my workshop. And it is a surprisingly small amount. Typically I use around three units on the Blue phase per month. Since the load is always balanced it follows that I use nine units in total. this is despite running some hefty motors etc. In a quiet month I may use three units total and in a very busy month I have been known to use 15 units. Though I must stress the last one was a one-off where I had some serious metal removal jobs in hand.

Compared with the total house usage around 650 units per month it is not worth bothering about.

[Mark RandParticipant @markrand96270]

Chris, the fact that you have 4kWp of solar panels installed, but are still on a rotating kWh meter implies that you are on the deemed export feed in tariff. At the moment, in this weather, your panels are probably generating 15-25 kWh per day, of which you are probably using 10-15.

While it is completely imoral, it is actually not only legal, but very sensible to get an inverter and a battery to save the exports so that you benefit from them when the sun isn't shining.

I got 4.68 kWp of panels installed on the shed roof in early January. The 8.2kWh battery that I had ordered didn't arrive until the third week in June. As a result of having the battery, my electricity consumption from and export to the grid, in kWh, have gone like this:-

April :- 286 in, 231 out
May :- 194 in, 264 out
June:- 150 in, 194 out When the Battery went in on 23/06/22
July :- 19 in, 59 out

 

In other words, the battery is saving me an additional 130-200kWh per month or a pound and an half a day at the moment on my tariff or £3 on current tariffs.

You'd get that benefit and still be eligable for the feed-in tariff payments. The inverter and battery would cost a bit North of £4,000, but that's a return on investment you'd have to do for yourself.

Edited By Mark Rand on 07/08/2022 20:06:29

[Howard LewisParticipant @howardlewis46836]

Calculating the cost should be just simple arithmetic.

Power in Watts is Volts x Amps. That tells you the Kw

The time, in hours, for which the power is used gives KwH.

So a 3 Kw kettle used for 6 minutes uses 3 x 0.1 KwH = 0.3KwH, or 0.3 Units of electricity, at say 20p / unit costs

6 p in UK.

Your Ammeter is probably measuring the current in one phase (If everything is to plan, all three phases will carry the same load )

So assuming that each phase to neutral is 240 volts, 8 Amps represents 960 watts per phase. So running the machine for 6 minutes, drawing that much current will consume 1.92 Kw x 0.1 hr or 0.192 KwH or at 20p per unit, 3.84 p.per phase

So 1 hour use of that machine should cost 38.4 x 3 p.= £1.152

Now someone more knowledgeable, tell me that we only need to consider current in one phase?

Howard

[old martParticipant @oldmart]

99% of my machining is done at the museum, there is no heating in the workshop, but the walls are double with about 100mm of foam insulator, so the temperature only changes slowly, condensation is not a problem. There may be led lighting in the near future which will save on the bills after flourescents.

[Howard LewisParticipant @howardlewis46836]

Have never measured the current draw for the VFD powering the 1.5 hp 3 phase lathe motor, or the 3/4 hp single phase on the mill. Probably not a lot, given that neither is ever driven anywhere its limits.

I think that the one time it was measured, it was circa 2 Amps.

The lathe has a 24 volt 50 W halogen worklight, so probably less than 10 watts from the mains. The mill has two worklights with 9W LEDS.

Considered changing the 60 /85 W fluorescent on the ceiling for a LED tube but the saving may take a long time to amortise the capital investment.

Howard

[not done it yetParticipant @notdoneityet]

With the old meters, I simply timed how long the wheel took for a turn or multiple turns. All meters had a turns/kWh printed clearly.

The later digital meters had a lamp which flashed every so often, depending on the load. The meter had the number of flashes/kwh on it. Counting the flashes, over a set time, is not that hard, for most.

The smart meter makes life so much easier to check out the usage.

The simple way is to turn off all other breakers at the consumer panel, to check the usage on any or each of them.

If on gas, using it for everything possible, is far cheaper than using a higher grade energy, such as electricity ( look up ‘grade’ if you don’t know what it means).

It may take longer to boil a mug-worth of water with gas, but is about half the cost of E-7 and a quarter of the day-time leccy rate. Look after the pennies and the pounds will look after themselves, as they say.

I would likely instal an electric shower – cheap if only turned on before soaping up and then to shower away the soap – but I know that my wife would have the shower as hot as possible, on maximum flow rate, for 15 minutes (or more) at a time. 2kWh (or more) nearly all just ‘down the drain’.

My virtually draught-proof workshop greets me with a (timed) 20W LED lamp, on entry, and I generally use one of two 20W LED lamps – depending on which leg of my ‘L’ shaped workshop I am working in – plus extra lighting at the machine in use.

The heating, to avoid condensation in the cooler months, is mostly taken care of by running the dehumidifier during the night for a couple hours, or so, on E7. Extra heat, for my comfort while in there, is supplied from a chinese diesel-fired air heater. I’ve nothing in there that will draw anywhere near a kilowatt of power, so I’m not really bothered about the small amount of energy used in my workshop. The small amount of oil burned is, likewise, not too costly (used from stock thus far).

My energy bill, for a semi-detached house (with just myself and my wife in residence), will not be anywhere near £4000pa come January!

I have a meter, like Martin 100 suggests, that is currently looking for a useful deployment. Also a couple (or three) power meters and several electronic timer switches that are used around the home/workshop wherever/whenever required.

[DMBParticipant @dmb]

EDF keep pestering me by text one week and email the following week, to have a smart meter. Replied that I am smart enough to work out how much it will cost to stick the kettle on for a hot drink and if I want one, I'll put kettle on. Keep your smart meter!

[DMBParticipant @dmb]

The frequently mentioned total cost of electricity is based upon what I consider to be a rather high "average" usage but my usage is nowhere near that. My DD is currently £73/month, has been since a year ago and I am in "arrears" by much less than one month's payment. "Do I look bovvered?"

[Nigel Graham 2Participant @nigelgraham2]

Dave (SOD) –

My mate is not a "silly old duffer".

When you are certified under one of the compulsory registration schemes like Gas-Safe, HETAS, etc, you have to keep up with all the frequent changes in legislation, British Standards etc.

He tells me searching for the latte now is a costly nightmare because the BSI charge the Earth for their services; while the annual refresher course these schemes demand cost several hundreds of £££. All right for a large company like British Gas, who can spread the cost around umpteen thousand customers; but a self-employed tradesman like him has to pay out of his own money while simultaneously earning no income for the several days of the course!

One thing he found was that usually the attendees on these courses know more than the lecturers, simply by experience as the equipment manufacturers bring out new or modified products; and of course are maintaining their practical skills far more widely than a college lecturer can..

I did not press him on why he regards smart meters as bad because I did not want to risk seeming to ask personal questions about his domestic arrangements; but the gist of it really was a matter of who benefits – and it is not the customer. Not technical but contractual and financial. The main problem seemed to be smart meters allow that the suppliers can do what the hell they like with the prices, at any time, without notice.

Also, it seems that a lot of customers who have opted for, or been badgered into, having a "smart" meter find it difficult to switch suppliers – though I don't think that's ever been straightforwards, has it?

.

This same plumber has also told me a heat-pump would of be of no use in a house like his (probably 1930-40s date, ex-Council estate, very similar designs to one in my town), for valid technical and practical reasons, as well as its capital and running costs – though at least he'd have no installation labour charges!

'

Usually I smell a fraud attempt coming: "I'm from the 'Windows' Corporation and your Amazon order…." and the like. I didn't realise the propaganda that you will all be forced to have a "smart"-meter within the next 3 or 4 years or so but it will be for your benefit, some 3 years ago now, were just as much lies.

Lenin is reputed to have said "If you want to know the reason for a law, ask whom it benefits". If he were alive now, he could just as easily replace "law" with "smart"-meter…. and no doubt anything else with that American prefix to its name!

[HopperParticipant @hopper]

When I put a split-system air conditioner in my insulated tin shed (2 car plus workspace size) I was worried about the running costs as it was a 7.5kW unit and running hard continuously all day in the very sunny daylight hours here in the tropics in summer. But when the power bill arrived, it worked out at $1 a day above the previous year for the same summer quarter. That's about 50P a day in your money. Best money I ever spent. I don't imagine the 500W lathe motor running now and then would make much difference, nor a few fluro tubes for lighting, by comparison.

Edited By Hopper on 07/08/2022 23:07:46

[NealebParticipant @nealeb]

I had been expecting someone to jump in with a warning about finding power consumption by measuring current and voltage and multiplying together. While that works for a simple resistive load (like a tungsten light bulb) it fails with more "difficult" loads. Motors fall into this category, as do a lot of electronics. It is because the alternating current is not in phase with the voltage – show the current and voltage on a graph and you will see the usual "wavy lines" of an alternating waveform, but the peaks do not align – there is a shift between them. This means that the power is not a simple multiplication. This is true even with devices like phone chargers – I use (like some others here) a cheap plug-in power meter from Maplins and if you measure voltage and current and multiply together you do not get the same answer as switching to measure power directly, which properly takes the phase shift into account.

So – beware of simple current measurements and converting to a power value!

[Tim StevensParticipant @timstevens64731]

Please don't be confused – the 'resistive load' of a tungten filament bulb is not at all simple. Its resistance is dependent on the voltage applied – being much lower as the voltage drops and the filament cools. This is why headlamps took some time to get up to full brightness – especially if the battery was elderly. The cold resistance being low drew much more current from the system, and only after the wiring had cooled again, and the dynamo was charging did the bulbs perform at anything like 'bright'. In fact, it is difficult to find a simple example of a resistive load in practice – they do exist, but few of the devices in the house or the shed are anything like 'simple'.

Cheers, Tim

[HowiParticipant @howi]

Posted by bricky on 07/08/2022 17:16:24:

As I have always got up early, I go into the workshop at 6 and use the machines on economy 7 until 8 it's surprising how much work can be achieved with 2 hrs uninterupted.The reason why I don't have a smart meter is that you have to pay by direct debit and the cost sometimes is more than I have in my current account by the end of the month.When I get the bill now I can transfer money to my current account as I do have other direct debits that need meeting too and a smart meter would catch me out.I think a lot of smart meter holders will be in for a shock.

Frank

my energy supplier lets me know well bofore it is due, that a DD payment will be taken, so your argument does not hold water.

If you are not paying by DD then you are paying more than you should, DD is the cheapest way to pay so you are shooting yourself in the foot.

as for smart meter users in for a shock! You obviously don't know how they work.

An interesting point about smart meters that has not been mentioned is that they take up to 15 minutes to update the readings, it is not instantanious.

As the price of energy has rockete, overall it showd I now regularly check my smart meter home display, overall it generally shows a steady day to day usage.

Background usage i.e overnight elec usage is about 10p per hour, gas about 2 to 3p per hour.

I could save elec by switching everything on standby off but I don't as it is more convenient to leave them on, this includes various clocks, TVs, computers,internet router and switch, central heating controller plus other on standby items.

While I would assume most on here will not be overly worried about energy costs, there are others in society that have a lot less income and will find rising prices will push them further into poverty.

There will come a point when the masses will say enough is enough and politicians will HAVE to do something.

[SamsarandaParticipant @samsaranda]

In respect of solar panels and batteries, I have solar panels capable of delivering 4kwh, I live on the South Coast and therefore placed to gain maximum gain from solar, on a sunny day such as we are currently having my panels generate about 25 – 26 kWh per day. I have installed batteries with 12 kWh of storage capacity, we are big users of electricity I have two large ponds in the garden with pumps and uv lights going 24/7. During June this year we used a total of 38 units of electricity drawn from the grid, the rest was down to solar, on many days we were totally self sufficient on solar, such that early morning just after the sun has come up we still had about 1/4 of the battery power left from the previous days generating. I calculated that our background usage of power with house and ponds together is about 400 – 500 watts per hour, every hour, so we use a lot of energy. The figures quoted above include the usage of dishwasher, washing machine, tumble drier all used during the day when the solar is producing at peak.I don’t worry about how much my workshop uses because in the summer it’s all covered by the solar generated power. When winter comes I will set the inverter on the batteries to charge them from the off peak electricity, we have an economy 7 tariff, so cheap rate currently costs us 18p per unit and full rate is 38p, so in winter during the daytime I will be able to use up to 12kwh at the cheaper rate of 18p per unit. Dave W

[NealebParticipant @nealeb]

Tim – I'm certainly not confused but as you might tell from the way I wrote, I was trying to simplify what is quite a complex (and I use the word advisedly) situation. I didn't even mention power factor! I would argue that a tungsten filament, once allowed to stabilise, is pretty close to a resistive load, but that's not particularly relevant. I just couldn't think of another simple household example. Maybe an electric cooker?

I've just done a quick check on my phone charger. With no phone connected, it takes 30mA at 243V. Simple multiplication would say that it is taking 7.3W. Switch to power measurement mode and it says 1W. I doubt that my cheap meter is particularly accurate, especially at these low values, but that's a big difference. On load, the difference is smaller and that will be generally true for motors and devices with big transformers as well. The lower the load, the more misleading the current measurement in terms of power consumption.

In short, don't trust a simple current measurement to estimate power consumption unless you know the nature of the load – it's good for working out an appropriate fuse/breaker rating but the days as far as it goes!

[Neil LickfoldParticipant @neillickfold44316]

Several years ago, we got a power consumption meter. It plugs into the power point and the device connected to it. It has no smart features , apart from the costings of the kw/h. It displays the total watts measured, and does monitor peak current or peak watts consumed. My circular saw draws 3kw on start up which was a shock to see, even though is sort of soft starts. But once running is not using much at all, around 250 watts, so far lower than I would have thought. It has been a handy little tool to use periodically. It can help you to charge a reasonable amount for the electricity used when making something, and I think we way under estimate how much power is used in the home workshop.

[Howard LewisParticipant @howardlewis46836]

As said, even the simple incandescent filament lamp is not a straightforward calculation.

Being in most cases a coiled coil filament must mean that that it has inductance, so there is phase shift between voltage and current. The calculation is corrected by incorporating the power factor.

Fluorescent lighting can be used to improve the power factor, where the major load is inductive, producing a phase shift opposite to that of the inductive load..

As I am only a simple mechanical engineer, an AMIEE should be able to provide a much more in depth explanation.

Howard.

Edited By Howard Lewis on 08/08/2022 10:27:36

[NealebParticipant @nealeb]

I was desperately trying to avoid a more in-depth explanation! Can we agree that there is no such thing as a simple resistive load, everything has associated inductance and capacitance (even the cables feeding the device), but as engineers we can accept a reasonable approximation?

There are probably a lot more mechanical than electrical engineers reading this so it seems sensible to avoid too much distracting and largely irrelevant (even if interesting to some of us) detail. "How much is this costing me?" also applies to intellectual effort needed to understand the answer!

[NealebParticipant @nealeb]

(Duplicate post)

Edited By Nealeb on 08/08/2022 10:43:28

[Oven ManParticipant @ovenman]

Posted by John Haine on 07/08/2022 16:02:41:

The cheap Maplin power meter I have shows watts and VA.

The old Maplin power meter is a great piece of kit. Mine is unfortunately reaching the end of its life as the socket has been overheating. I have searched a lot for a similar replacement but none of the modern offerings seem to be anywhere near as good, they all seem to have the same basic guts. Does anybody know of a model that would offer the same features as the Maplin unit with the same idiot proof user interface.

Peter

[J HancockParticipant @jhancock95746]

Surely , the most inefficient use of electrical energy in the home is to create heat directly , ie the oven and immersion heater ?

[BazyleParticipant @bazyle]

Although the advertising for smart meters has at times been reprehensible (exploiting grandparents concern over grandchildren) they don't bite so not a major problem. Mine does get a bit confused over summer time and the cost display is a bit off after resetting itself at midnight for a while. As to accuracy when I was away for a week so stable loads (fridge, alarm, radio on standby) the daily readings were within a penny which could be the variation in the fridge and ambient temperature. I think if I add the modem and a security light my base load including standing charge is about £1 / day now.
Having had to get a new fridge last year it is now obvious how much less it uses, and I can see the jump in watts each time it turns on. Just unplugged my microwave and see it uses 6W, that would light up the whole kitchen if it were a LED bulb, Modem is a bit of a pain at 11W. Mains radio uses 5W to keep its channel memory and about 20 running which is probably rather more than a modern one would. When outside I use a solar powered radio.

Oh, the remote smart meter display uses 1W.

As to workshop machine power consumption this might be a reason to get a SuperAdept for the small jobs and forgo the boasting of having a Colchester Triumph. I took my smart display into the workshop and did a five minute turning job, The display didn't even move !W no matter how hard I treadled

[SillyOldDufferModerator @sillyoldduffer]

Posted by Nigel Graham 2 on 07/08/2022 22:53:46:

Dave (SOD) –

My mate is not a "silly old duffer".

When you are certified under one of the compulsory registration schemes like Gas-Safe, HETAS, etc, you have to keep up with all the frequent changes in legislation, British Standards etc.

…

Lenin is reputed to have said "If you want to know the reason for a law, ask whom it benefits". If he were alive now, he could just as easily replace "law" with "smart"-meter…. and no doubt anything else with that American prefix to its name!

With respect Nigel we all become silly old duffers, some of us before leaving school!

Is it relevant that your friend is in a compulsory registration scheme? I think not, particularly as it seems the chap in question is a plumber.

I'm not here to sell smart meters, and my advice to Chris was not to get one. My reasoning is smart meters are a tool, and the smart meter is a tool that doesn't meet Chris's need to understand how much his workshop machines cost to run. I recommended a wattmeter, which does. They're plug and play: buy one with cost calculation built in and and it does the sums too.

By thinking of smart meters as a tool and asking 'will it work for me', just as if I was buying a screwdriver it's not necessary to get entangled in red-herrings like the cost to an independent tradesman of keeping up-to-date with British Standards, or what the Law is for, or what Lenin said, or Internet fraud schemes. It's unhelpful to introduce these into Chris's "what is this costing me?" question.

A few people have commented that smart meters aren't essential. Quite right, but not enough to conclude they're useless or evil. Smart meters make it much easier to keep tabs on the cost of consuming electricity. They monitor consumption and issue alerts continuously, which is extremely helpful to anyone on a tight budget. May not have been critical in the past, but it is now. They're not for well-funded people living in electrically simple circumstances who know how to read an ordinary meter and will do the sums regularly. (As opposed to the experts who know how but can't be bothered!) Smart meters are for the bulk of the population who don't have technical skills, living lives stuffed with difficult decisions, with multiple complex demands on their time and money. They're much more useful to the working millions than to retired Model Engineers like me!

In general I think it best for engineers to avoid taking personal experiences into account. We are not politicians who look ahead and then run sideways like crabs. Evidence and intellectual discipline please, and remember that opinions based on small numbers are always highly suspect. That a Smart Meter is of no use to me doesn't mean they're all rubbish. You have to understand the big picture.

Dave

[Anonymous]

Posted by Nealeb on 08/08/2022 10:42:45:

…there is no such thing as a simple resistive load, everything has associated inductance and capacitance…

Strictly true, but in the case of an incandescent filament the associated inductance and capacitance will be very small, less than a microhenry and a few picofarads. At 50Hz a resistive model is rather better than reasonable.

The older electromechanical watt-hour meters measure energy consumed, they do not account for VARs. The newer electronic meters do take account of power factor. The case of wall warts is more complex. The current is drawn in pulses so the waveform is nothing like a sinusoid and contains a lot of harmonics. This is a problem for generators, so the power supplies should contain power factor correction circuits these days. These can be passive, ie, a filter, ot active, usually a switch mode supply controlling input current according to the input voltage.

My experience is that my workshop consumes very little power compared to everyday things in the house. The only thing that did make a noticable difference in the workshop was changing five flourescent tubes for LED tubes. I use about 6.5kWh per day, on average, for everything.

Andrew

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