Lossing around 150 watt, ideas on what?

[ericmark]

I have a clamp on meter that measures whole house power use, it shows between 170 and 250 watts most of the time, with freezer and fridge freezer stopped around 180 watt, I know it's on the rings, it seems about even on the two rings, and using a plug in energy meter around 20 watt for TV on stand-by and with lap top and phones on charge can explain around 50 watt per circuit.

So seems using around 100 watt more than I should, up until this week I could not switch off circuits, now each circuit on it's own RCBO so know on the socket circuits, but just can't work out what could be using the power.

Not a huge amount, but wonder if it could be some device fitted by previous owners, and wonder what it could be and where it is?

 

[Harry Bloomfield]

20 watt for TV on stand-by and with lap top and phones on charge can explain around 50 watt per circuit.

The standby TV is much more than I would expect, I would expect not more than 1w for a modern TV, the other items seem to high too.

Why not just go round and switch everything you are aware of, off, then check again to see if there is any unknown consumption?

 

[JM2]

I'm unsure of the accuracy of these things at the bottom end; what does a real clamp-on meter show as the current draw ?

 

[ericmark]

I have three plug in energy meters, two connect to PC one is stand alone, I see freezer uses 62 watt when running and the Scottish power meter shows around 62 watt more when running, and with the display plugged into flat switching off both house ring finals shows zero usage, either one switched on and about equal at around 85 watt each, but from flat can't hear if fridge and freezer are running or not, so hard to be sure exactly what each uses, clearly have to test in daylight so no lights on.

So been moving the energy monitors around, the main Sky box has to power the LNB so TV and boxes 20 watt, just thought of one I missed I have a satellite box in my room will try turning that off tomorrow, 50 or so watt is not that much, but niggles me that I can't explain it.

 

[winston1]

I have a clamp on meter that measures whole house power use,

No it doesn't. It measures the current (it is only a current transformer if it is clamp on). It then gives a reading in watts assuming a fixed voltage (which you don't have) and unity power factor (which is also unlikely).

When you have a power factor less than unity it will read high.

 

[ericmark]

OK my plug in meter measures power factor and voltage as well as watts and amps, but measuring amps even if the display shows watts is close enough, the device was used before smart meters to get a closer estimated bill than other wise possible with Scottish Power and the correction after meter reading was within £10 that's not bad, and clearly cheaper and easier to fit to smart meters.

 

[ericmark]

 

[JM2]

I meant a real current clamp-on (am)meter - but if you're happy your gadgets read true low down then just serach for the missing devices (it can't take that long to unplug everything).

- I hope it isn't all those energy meters you've got!

 

[magicmushroom666]

Aerial booster in the loft perhaps?

 

[JohnW2]

OK my plug in meter measures power factor and voltage as well as watts and amps, but measuring amps even if the display shows watts is close enough, the device was used before smart meters to get a closer estimated bill than other wise possible with Scottish Power and the correction after meter reading was within £10 that's not bad, and clearly cheaper and easier to fit to smart meters.

In terms of averages over time, variations in voltage and power factor 'average out' and really do not have any appreciable effect on accuracy. I use a monitoring system based on clamped-on current (only) measurement, but as the below shows for my night-time usage, conversion of that to kWh with assumptions of a constant voltage of 240V and a constant PF of 0.98 (initially determined empirically) results in figures which are incredibly close to the (true kWh) data based on my ('dumb') meter. Over the ~2.5 years illustrated below, I have used a total of about 10,000 night-time kWh, and the difference between the meter's cumulative figures and my current-derived ones is, today (after those ~2.5 years) a mere 19 kWh (i.e. an error of about 0.19%).

It's obviously different when one undertakes real-time or short-term measurements, since uncertainties about voltage and PF can sometimes result in current-derived kWh figures being quite inaccurate.

Kind Regards, John

 

[ETAF]

tv & audio systems on standby , any radios on standby , Electric Clocks, Central Heating Pump/Boiler, smart lightbulb , smart plug, touch controlled dimmer, fridge, freezer, Oven clock, hob - mine has a timer and always on with touch, Microwave clock, cordless Telephone base unit for Messages or charging phones, Dishwasher with timers etc , coffee machine with a heater plate , warming draw on oven, rechargeable vacuum cleaners on charge , ironizers , broadband router , printer on standby , desktop/laptop PC on standby, plugged in, screen plugge in , washing machine on standby, mine has some sort of smartphone connection and a LED light is always on , garage anything plugged in, I have a amp in the loft for TV's powered from main TV so always ON
These are the sort of things I have on at my home

 

[SimonH2]

There's probably a lot of things that take "very little" power but have a very poor power factor when "off". These are likely to fool many simple clamp on meters which will be operating at the extreme lower end of their range where accuracy will be questionable before you even start.
Many years ago when I was an apprentice I remember watching with some personal amusement as a supposedly qualified and experienced electrician struggled to understand why a board he was testing (prior to installation) was tripping the MCBs. The board comprised a 4way DB and a contactor to control 4 large floodlights - and the power factor correction caps were fitted on the board. My suggestion that the current through the caps was tripping the MCBs was met with "capacitors don't pass current"
A lot of things look like capacitors when "off", and it can add up to significant current. But it's not "real" power and you don't get billed for it.