How Much is this Costing Me?

You should be asking why the price keeps going up and why they're now preparing us for a £4000 annual bill, come January next year.

Martin.

Greed

H

Exactly so. Heating and lighting which are on for most of the time are big consumers compared with machines that turn on and off.

I measured my lathe back in 2018:

My lathe is a WM-280 fitted with a 1500W 3-phase motor, VFD and two continually running cooling fans. (One on the motor, one on the VFD). How much power does it actually consume in operation I asked myself?

So with belts set to the high-speed range; banjo gears set for fine feed; auto-traverse engaged; and the built-in gearbox set to the finest feed-rate:

• Lathe switched on (ie. with only the fans and electronics running) - 47W
• Motor idling at 150rpm - 210W
• Motor spinning at 1500rpm - 360W

Using 13.7mm o/d steel welded gas pipe as a test piece with carbide inserts and no coolant/lubrication:

• 0.3mm deep cut @ 1500rpm - 542W (A 0.3mm cut removes 0.6mm from the diameter)
• 0.5mm deep cut @ 1500rpm - 540W
• 0.7mm deep cut @ 1500rpm - 565W
• 1.0mm deep cut @ 2400rpm - 960W ( A 1mm deep cut removes about 80 thou from the diameter.)
• Parting off with a 3mm wide carbide blade @ 1000rpm - 600W, lower than expected.

At the finest feed rate (0.07mm per revolution), a 23mm long cut takes about 20 seconds at 1000rpm. I'm too befuddled this morning to calculate how much steel I can remove with 1kWHr's worth of electricity costing me about about 11p.

Taking 2mm off the diameter of a steel rod in one cut is pretty much the hardest I ever drive my lathe in practice. In this test doing so produced a string of smoking blue swarf from the gas-pipe rather than chips. At that rate the lathe pulls less than 1kW, which suggests that I need to drive the lathe significantly harder to stress the motor, and thus have the opportunity to make the carbide inserts work better. On the other hand an unstressed hobby lathe will last longer! (I've no idea what this lathes operational sweet spot is. My car is best if I drive it at a steady 60mph. Lots of stop-start slow speed city motoring is bad for it, as is hammering up and down a motorway at 90.)

Interesting that the belts, banjo and gearbox in fine feed eat a couple of hundred watts before any useful work is done.

Normally I guess I have the lathe burning about 550W during cuts. That's only a couple of amps from a domestic mains socket. I use more electricity lighting the workshop and making tea than I do cutting metal!

Reassuring I hope except for the rising price of electricity! Writing in 2018 I quoted electricity costing 11p per Unit. In Aug 2022 it's about 28p per unit, with more heavy increases on the way: one source suggests 78% in October, with another hike next year in the queue. Previously the Ofgen price cap was set annually. Now it's being reset every 3 months because wholesale prices are rising so rapidly.

Although the cost of running workshop machinery is unlikely to be a problem, managing energy overall is becoming a priority! Nigel recommends not bothering with a smart meter because his mate in the building trade says so, but we need to understand why! There's a danger the mate is an old duffer who hasn't twigged yet that energy is rapidly getting scary expensive! Even rich folk are feeling the pinch. The happy slapdash days when householders could leave 100W filament bulbs burning for weeks on end are over. A smart meter is worth having if it helps households manage energy. I know how to check my ordinary meter but it's a right pain to open the box and do the sums. In contrast my daughter's smart meter is easy to read, and flashes red and sends her text messages whenever limits are exceeded. Better if smart meters weren't necessary, but they probably are...

I fear cheap electric bills are going the way of the Tram, Steam locomotives, and industrial Canals.

Dave

My experience with Smart meters is they tell lies.

Ours never shows the tariff we are on, and will often show different readings each morning when the same things have been running overnight. Not to mention the times when it is not working at all.

An old style electric meter wired into the workshop supply would give a much better reading.

Regards

Gray,

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.

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.

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

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

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.

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

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.

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!

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?"

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!

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

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!

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

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.

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

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!