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Your basic physics is spot on with one important addition: that formulae works for DC (direct current) only. With AC (alternating current) the voltage and current fluctuate more or less like a sinus curve over time. Also, the voltage and current are out of sync. Practically speaking the current lacks behind the voltage. In order to calculate wattage for AC you need to compensate for this "lacking". It is usually known as the load factor. The load factor is always less then 1, so your wattage ends up less then just multiplying volts times amps.

Jeroen

Oh, I never knew that! Thanks.

lacking: do you mean lagging? ie following on behind?

Not timers, but thermostats. For most (non-inverter type) refrigerators, the compressor runs until it reaches the desired temperature (that cool-cooler -cold-coldest setting knob) and then stops until the temperature is a bit higher than the high threshold. So, if you wanted it to be at 6 deg C, it might go down to 4 deg C and stop. Next as the temperature rises inside, the thermostat will again start running the compressor when the temperature inside reaches 8 deg C and so on.

Yes, your are correct it is following behind. So if you know the wattage you just multiply by hours divided by 1000 to get kWh. However, as you already noted it doesn't run continuously so you need to correct for that.

How often the thermostat kicks in and switches off depends on many factors. Ambient temperature, the temperature of the stuff you just put in and how much. But also the state of the fridge itself. Most fridges over time become less efficient which means effectively they need to run longer to maintain a certain degree and or to cool down to that degree. Just like a car AC.

As the saying goes, the best place for a fridge is in the coldest place in the house!

Jeroen

Thank you guys for the quick responses.

So taking the power factor of refrigerators as .5 , one runs at 100 watts and the other at 120 watts.

Assuming they work 25 % of hours a day on average throughout the year for North Indian temperatures (somebody correct this if they have better data),they consume 600 and 720 watts per day respectively.

That is .6 and .72 kWh per day respectively.
Or 219 and 262.8 units of electricity per year respectively.

Does that seem about right?

Power factor will not be that bad for the units. You can consider power factor to be 0.75 for the calculation .

And the fridge will warm it up!

Another thing to remember about fridges is that a full fridge is more economical than an empty one. If your fridge has little or nothing in it, every time the door is opened, whoosh... all the cold air falls out. And the fridge has to start cooling down the interior again. But all the stuff in the fridge "stores" coldness.

Ok let us see how all of these collective insights add up:

So we want our fridge in a space that is as cold as possible, but as the fridge will warm it up it needs AC in order for the fridge to run as economically as possible.

Further more, it needs to be absolutely cram packed with stuff. Preferably this stuff is chilled down before it is put into the fridge.

The last thing to bear in mind when it comes to running fridges efficiently is to, never, and I can not stress this enough, never ever open it!

Power consumption will be minimal (well at least for the fridge)

No wonder my mum did fine with no fridge when we grew up!

🙄
Jeroen

I had done a study of my Fridge a few days back with my new toy bought from amazon!

Here is the earlier post:
http://www.team-bhp.com/forum/gadget...ml#post4409213

The fridge consumed 2.44 units(KwH) over a 24 hour period (Assuming the meter is reasonably accurate).

So my 13 year old 6.5 kg LG Top Loading washing machine's outer body has rusted badly & is developing holes and is peeling away. The machine otherwise working fine. Is there anything I can do about the body or should I just a buy a new one?

Check with Junk Dealers if a similar machine has been junked and you can salvage the body.

In general there is no point in spending good money on old appliances, as you do not know when some thing major requires replacement.

I suggest that you buy a new WM and sell this off.

One can go to a fabricator and get the old panels removed and install new steel panels of appropriate thickness. Or you can get the holes repaired as one would on a car.

Planning to buy an Induction Cooktop since we are planning to travel with a toddler. Hence being lightweight is a key requirement. Can folks recommend a reliable one which is not very heavy?

I was looking thru Amazon.in based on user reviews as well as weight (sub 2kg) and the Prestige Cooktop seems like a good buy: URL

However, I would trust recommendations from BHPians more than Amazon user reviews and hence the post. Please advice :thumbs up

Went in for an LG 4 star rated 420L fridge. This is rated for 230 units of electricity a year by BEE, but the salesmen were of the opinion that it could take 1 unit per day max, and my initial observation is that it takes close to 1.5 units a day. Still way better than the 4.5 units sipped per day by the old 460L LG refrigerator.

Not exactly an appliance question, but has anyone purchased Paffy brand items from Amazon ? How are they ? Are these chinese products ?

that was pretty close ! And glad that the consumption has reduced now.