electricity "meters" like current cost, killawatt, owl, etc

[PeterC]

I had a free meter with a clamp and WiFi to the monitor - it was so bad that I gave it away to an electrician!

The plug-in meter from Maplin at least shows, e.g., a 20W CFL as 20W and about 38VA; it also shows the PF-corrected 30W CFL as 30W and 31VA. Most of what I want to know runs from 13A plugs and so I can measure it (even the PC on, of course SMPSU, seems to be quite accurate at 45W as the

330W PSU never gets warm). I haven't bothered to measure the Humax FS PVR as it has to be on when required anyway - if I get a tuit...

The items that don't plug in are resistive mainly, except for the boiler.

Overall I know pretty well what the power and energy are and an accurate clamp-on meter would be interesting but academic.

[Adam Funk]

I have one of those (on loan from the local library) & noted that neither of the components (the clamp-on ammeter & transmitter; the receiver & display) plugs in --- they both run on batteries --- so there's no way for it to measure the phase difference or power factor.

I have a socket within 1 metre of the meter, so I could use something with a plug-in ammeter-transmitter, but is that an unusual layout?

In a domestic situation, the OWL will never under-read, since domestic customers are charged for kWh rather than kVAh --- is that correct?

[Dave Liquorice]

Well I wouldn't like to go that far but I did the maths on several providers when the "no standing charge" tarrifs came in and and occasionally since and found that when you had used all the, expensive, Teir 1 units you had paid the standing charge. The Tier 2 unit price was the same as the single rate "standing charge" tarrif.

Not obvious? You pay more fo X amount of something and have something else removed and it's not obvious that the overall result is likely to be the same or very similar?

AFAIK there is only one true "no standing charge" tarrif out there, from EBICO. If you don't use any power your bill is zero. The unit cost is higher, 14.08 v 9.04 here, but most most standing charges are well over

10p/day.

But the sheer number of tarrifs out there is stupid, I'm not convinced that the goverment dabbling with them is good idea though.

[Andrew Gabriel]

For most practical purposes, probably yes. It would underread if your mains voltage was higher than it was set to or guessing.

I don't know how accurate it is at handling a heavily non-sinusoidal current waveform - for example, if it derives something other than the RMS value, then it's not even giving you the VA rating, and you might be getting something either higher or lower than the real value.

[Tim Streater]

We're on ScottishPower and if we were to use zero we'd pay zero. It's a NSC tariff, and there are the expensive units and the slightly less so ones.

OK I just checked ScottishPower's Sept 14 deal. That is NSC only. There are limited payment methods. Their April 2015 deal by contrast has both types and more payment methods.

It takes a certain amount of poking about to find these pdf's to download which have all the details of their deals.

[Dave Liquorice]

Zero use was a bad example. Say the first 500 units are Tier 1 at 20p, Tier 2 is 10p. Ebico 15p.

Use 500 units: "No standing charge" 500 * 0.20 = £100 Ebico 500 * 0.15 = £75

Use 1000 units: "No standing charge" (500 * 0.20) + (500 * 0.10) = £150 Ebico 1000 * 0.15 = £150

Almost impossible on some suppliers sites and when you do finding the tarrif for your area and then all the caveats in a 20 page .pdf ain't easy either. If there is one place that could seriously do with tidying

up and making consistent across all companies is the finding and presentation of the tariff information.

[Chris J Dixon]

Absolutely, it is done quite deliberately, and is similar to banks constantly changing their accounts so that existing customers find themselves on pitiful interest rates.

However, whilst the government's attempts to simplify matters is welcome, the result is likely to be a leveling of existing rates, which will mean that those of us who have managed (or hope we have) to get a good deal will find themselves having to pay more in future.

We would all like to pay less than average, and it isn't going to happen :-(

Chris

[Gazz]

Even if there wasn't a plug nearby, bit of wire sticking out the receiver and a couple of pins to stick through the insulation of those big wires the clamp goes round :)

I thought similar, but figured as the RX unit plugs in, couldent they have used an AC wall wart instead of a DC one, done the rectifcation inside the meter, after getting the wave form data from the incoming AC signal, prolly wont work as the wall wart is a SMPS, but i dunno,

Seems all these meters don't bother about power factors etc, even tho enough people comment on it being something much desired.

[PeterC]

I'm with Ebico and every time I've looked at comparison sites they've proudly declared that they can save me -£x, where x can be £5 upwards, then say switch now! One company sent me a letter, after I'd looked on such a site, to tell when I'd be switched from Ebico. I got in touch with Ebico and it was sorted PDQ. Also, if I'm ahead on the gas at the end of the 'summer' there isn't a refund but at the end of the winter it's just about right.

I'm hoping that the gov.'s interference doesn't bork everything - I do not want standing charge or front-end weighting on electricity of 250 -

350kWh/Q!

[Adam Funk]

Good point, I forgot about that. The OWL lets you pick the voltage from a fixed list (IIRC, 110, 120, 230, 240, & 250; mine is about 246 according to the Maplin plug-through meter, so I use 250).

Where would you get heavily non-sinusoidal currents in domestic use?

Also, how low is the power factor likely to be in a house?

[harry]

You won't except in certain electronic devices. The sine wave is generated in rotating electrical generators except in very rare cases, Where 99% of all our power comes from.

An uncorrected electric motor may give a power factor of around 0.7. (Varies on level of load.) Heating loads have a power factor of unity (1)

From a power usage point of view, you can ignore power factor, your electricity meter takes no account of it.

[harry]

The voltage you get varies hugely depending on many factors. It is nominally these days 230V Mine varies between 220 and 260 volts.

[Andrew Gabriel]

The strangest one I've seen from a commercial product is my microwave (non-inverter type).

The strangest one I've seen is in something I designed myself, which is a voltage dropper for operating a 120V cooking appliance on 240V. I chop out the centre of each half cycle, so I'm only drawing current during the lower voltage parts of the sine wave (which is the complete opposite of many electronic loads nowadays).

I think that's only products over 25W (certainly it's 25W for SMPSU's integrated into lighting).

Typically, they draw current only during the +ve and -ve mains voltage peaks. Actually, linear PSUs were pretty much the same (and that's because most SMPSUs start with a linear PSU).

An exception is dimming switched mode PSUs designed for an ordinary (triac, phase control) dimmer, where the SMPSU omits the smoothing capacitor, because it needs to not operate during the 'off' period of each half wave. Electronic 12V halogen lighting transformers are of this type. So were some dimming CFLs (cold cathode types, but they seem to have vanished now).

[Dave Liquorice]

Presumably pushed 7 V over spec by them as well. Unless it's just more normal harry bullshit.

[harry]

Yes it does. The voltage rises when I'm exporting. About two volts as far as I can tell. It was a lot more variation until they put a bigger transformers in.

[harry]

There is an AC (and DC) voltmeter on the inverter. Also AC/DC current, frequency, Kw, Kwh, Day/date/year (I don't believe they are particularly accurate) and a graph of the daily power generated. Plus lots of self monitoring crap.

Oh and £. So long as you tell it the cost/Kwh.

[Fred]

I think that these meters give a faster response, i.e. you can run around the house switching sockets off individually and seeing the drop there and then, rather than switching off one socket per day and measuring the difference each morning.

[Tim Streater]

I got one of these:

for measuring individual devices. It understands power factor, too.

[Adam Funk]

You can also see how much difference switching lights off in unoccupied rooms makes.

That's good for finding out how much energy the various dishwasher & washing machine programmes use, & for learning that most of our wall warts use no measurable power when plugged in but not charging.

[Adam Funk]

I doubt many people have that! Interesting idea: what are the advantages & disadvantages compared with a transformer?