Just how much power can a fan oven consume...?

[Peter Kemp]

Folks,

We've recently moved and I've finally got around to checking the flat's energy consumption.

So I start this morning:

08:00 'day' meter reading 8159 09:00 'day' meter reading 8160 10:00 'day' meter reading 8161 11:00 'day' meter reading 8162 OK, one unit or so an hour 12:00 'day' meter reading 8166 What??? 13:00 'day' meter reading 8167 Back to one unit an hour

What happened between 11:00 and 12:00? My wife put the fan oven on for

15 minutes, to heat up a pie. That's right - 15 minutes. Nothing else in the flat changed during that time.

How can a fan oven consume 3 kw hours in fifteen minutes? It's a run-of-the-mill single Bosch fan oven - that's a 3 or 4kw load rating?

To my understanding, the figures suggest the oven was running at 12 kw for that quarter of an hour (some 48 amps) which doesn't seem plausible.

My first thought is that the meter is faulty, but I'd like to know of other possibilities.

Can anyone offer enlightenment?

Many thanks, Peter

P.S. This wasn't a fluke. Mid-afternoon, I ran the oven for another 15 minutes and whoosh, another four units gone over the hour (ie the base load plus three).

[charles]

Is the meter realy displaying kWh?

[Andy Champ]

TBH a kW standing load seems a bit high too... have you tried turning things off to see what it does? You ought to be able to get it to negligible (clocks only) without too much trouble, then turn on a couple of lights of known power...

Andy

[Peter Parry]

Simple, it can't.

Possibly only a fraction of that, many Bosch single ovens are less than 1kW.

[Andrew Gabriel]

I'm guessing the pie said heat for 15 minutes. How long was the oven left on to warm up? What sort of hob do you have? Electric rings can use a lot if something was also heated on the hob.

Your readings do sound rather high.

The heat from the oven and much of the heat from a hob all goes into heating the house, so if you do generate 4kWh from these, your heating system (if it has suitable controls) will demand

4kWh less than it would have done.

As Andy said, a base load of 1kW is quite high. Mine is around

500W, and that's with more always-on equipment than I would expect most people to have, although it is averaged over whole quarterly billing periods, not just the middle of the day.

[Johann Klammer]

If there was some manual dishwashing done at the same time, a boiler may have kicked in, too.

[RJH]

1 kWh ambient is a lot, especially if it doesn't include heating. That's £1500 a year on its own. I'd look at your method of measurement first.

Rob

[Peter Kemp]

Thanks for the thoughts so far:

1 I agree a standing load of 1Kw is kinda high and needs investigating. The issue with the cooker became my first priority.

2 When I quoted kilowatt hours, I was assuming that the meter's units were kwH. Is that not the case?

3 The oven was on for fifteen minutes in total. It's a fan-assisted oven, so it gets to working temperature pretty quickly. When turned off, the fan continues to run for about five minutes, but I've assumed that's trivial consumption.

We're going to shut down the house completely tomorrow (apart from the fridge) before going out shopping for a couple of hours. I don't expect the meter to budge. When we get back, the oven goes on for fifteen minutes while I stand and watch the meter. If another three units go up in smoke during that time, I guess it's a phone call to EDF.

Wish me luck!

Regards Peter

[Paul Herber]

Are you sure you aren't reading the 1/10ths of a unit digit?

[charles]

It might not be. Have a good look at the front plate. Mine is labled as a "Watt Hour meter"

[Dave Liquorice]

No kettle full of water for a cuppa to go with your pie?

No more lights going on in the kitchen to see to do the oven/pie/kettle?

Lots of people saying 1kW base is high, but it's not far off for an occupied place with people doing things. Taking the monthly/quarterly amounts and dividing by the appropiate number of hours for the period gives an hourly for the *whole* period. But over a given day the hourly average base load will vary, night with most things off, will be much lower than say the evening lights, TV, PC's etc all on... Our night time base load is about 300W, evenings over 1000...

Hum... certainly appears that something odd is going on.

[Dave Plowman (News)]

You can heat a pie in a conventional fan oven in 15 minutes from cold?

[John Williamson]

Check whether your meter is showing a decimal point or not. If you divide those readings by ten, inserting a decimal point between the last two digits, they make perfect sense.

I have a similar problem with another, totally unrelated, type of meter that transmits readings without inserting the decimal point, so they show up as ten times their true value.

[Brian Gaff]

Yes, I agree the meter sounds like its not reading what you think it is, its obviously working to a different unit than might be expected. I did ask this question once and never did get an answer I could understand. Basically they said the meter serial number tells us how to interpret the reading. Which means, in my book if I could read it myself, which I can't, how the heck could I calculate the usage if I did not know what its unit of measurement was in the first place.

Brian

[Dave Liquorice]

Doing the maths backwards 17p/unit. Which is perfectly possible to have

these days even with a "standard" tarrif. Our E7 day rate is 18.78 + 5%

VAT...

[Dave Liquorice]

Oven from cold with pie in or oven pre-heated then pie in? All the oven based cooking instructions I can remember all have pre-heated in them.

[RJH]

Yes - I used 18p, but the tariff system is confusing in the sense you're never comparing like with like.

1KWh background (that is, at night say) - 2 old freezers and larder fridge, one old PC 24/7, 3 or 4 20W standby appliances (phones, printer)?

With a bit of thought, some expense and very little loss in convenience my 4 bed home idles at 80W - fridge, freezer, gas boiler electrics, and LEDs for often on lamps.

Rob

[polygonum]

When (many years ago now, I confess) I had a Bosch oven, the instructions said something like "no need to pre-heat". And, with few exceptions, it worked fine.

OP (or person actually heating pie) might simply have had the oven on for 15 minutes but left pie in for longer. It is often perfectly effective to switch at least the over heating off before food is finished heating through.

[AC]

Phone EDF? Brave man.

[Dave Liquorice]

Tariffs are confusing but the various comparison sites tidy that up a bi t but you still need to look at the actual unit prices and you actual useage rather than take their "savings" figures.

18p is expensive though, our other supply (that gets most use) is 9.04p/unit.

1kW at night with everyone asleep would be high but is reasonable for when people are up and about. The times the OP mentioned and produced th e 1kW/hr base load were when he and his missues where up and about...

I must investigate our 300W night load as it's pretty steady for hours. I don't see 50 - 100W steps that I would expect from fridges/freezers cutting in and out. They are all A class though so perhaps they don't actualy come on all that often in the wee small hours.