The Green Kitchen - The Year of the Fridge
January 13th, 2008
Since ‘The year of the Fridge’ appeared in The Times on Sat 5th Jan, we have had a number of emails asking questions about how to best use the Plug-in Consumption Monitor with a fridge or freezer, what results to expect and how to translate that into running costs.
Feel free to ask any questions / make any comments at the bottom of this entry, no need to register or anything. All questions will be answered.
How Fridges & Freezers work
Fridges use a thermostat to control the temperature. When the temperature inside the fridge becomes too warm the cooling mechanism is switched on until the temperature is lowered and the thermostat switches the cooling system off.
Throughout the day the fridge constantly cycles on & off to maintain the temperature.
How to use the Plug-in Power Monitor with a Fridge / Freezer
If you look at the bottom half of the Plug-in Consumption Monitor page, you’ll see the various modes the meter has. Two of the modes are of interest to us here:
Mode 1 - Wattage Display
This mode will tell you how much power (in watts) is currently being used. It’s great for measuring anything that draws a steady current such as a TV / DVD / Freeview etc on standby but not ideally suited to a fridge or freezer.
If you were to use this mode on a fridge you would see it spends lots of it’s time using little power at all and some of it’s time drawing maybe 100 watts or so when the cooling system does switch on.
Mode 2 - Cumulative Display (KWh’s)
This is the mode to use for a fridge. You want to measure the number of Kilowatt Hours (kWh’s) used over a 24hr period. This figure will tell you how efficient your fridge is and allow you to calculate the daily running costs.
Step by Step guide
- Remove the fridge plug from the wall, plug the meter into the wall and the fridge into the meter.
- Put the meter into ‘kWh’ mode - keep pressing the FUNCTION button until a small ‘KWh’ appears in the top right hand corner.
- Zero the cumulative kWh reading - do this by holding the SET button down for at least 5 seconds.
- Leave your fridge / freezer to run normally for 24 hrs then note the kWh reading.
During the 24hrs it’s OK to flick between the different modes (Watts, Amps, Voltage etc) this won’t affect the cumulative total.
Manufacturers often quote the number of kWh’s per year for their fridges. To find your yearly usage just multiply the 24hr figure by 365.
Example readings
 Old Fridge Freezer - 3.93 kWhOur old Fridge/Freezer (roughly 6ft high, half fridge, half freezer) consumed 3.93 kWh’s in 24hrs. |
 New Fridge - 0.34 kWhOur new energy rating ‘A’ fridge (large fridge, 5ft high) consumes 0.34 kWh’s in 24hrs. |
 New Freezer - 0.46 kWhOur new energy rating ‘A’ freezer (normal under-counter size) consumes 0.46 kWh in 24hrs. |
What does it cost to run ?
You need to look at your electricity bill and find the cost per kWh. You might find there are 2 rates here. For energy saving purposes, you should use the band from which the savings will come from.
Here is part of our bill (Nov 2007 prices). We would use 10.16p + 5% VAT = 10.668p per kWh.
To work out the running costs for 24hrs, simple multiply the kWh’s used by the cost e.g.
Old Fridge/Freezer = 3.93 x 10.668p = 42p per day = £153 per year.
New Fridge = 0.34 x 10.668p = 3.6p per day = £13 per year.
New Freezer = 0.46 x 10.668p = 4.9p per day = £18 per year.
For us, the saving would be £153 - £13 - £18 = £122 per year. That’s just the financial saving, add to this the environmental benefits!
The Next Step
The best plan of attack is simply to check out everything in your home that has a plug. Make a note of the item then see how many readings you can take from that one item e.g.
Constant power consumption (Use Mode 1 on the Plug-in Monitor)
- DVD player on standby - 4 watts
- DVD player on but not playing - 10 watts
- DVD player playing a disk - 14 watts
- Laser Printer on standby - 3 watts
- Laser Printer Printing - 1000 watts
- Dehumidifier on standby - 9 watts
- Dehumidifier working - 170 watts
- Desktop PC - 112 watts
- PC Peripherals - 36 watts
- PC & Peripherals - 148 watts
- TV Ariel booster - 3 watts
- Sky+ on Standby - 13 watts
- Sky+ Playing - 20 watts
Energy required for a task - (Use Mode 2 on the Plug-in Monitor)
- 24hrs Fridge - 0.34kWh = 3.6p per day = £13 per year
- 24hrs Freezer - 0.46kWh = 4.9p per day = £18 per year
- 12hrs PC and Peripherals - 1.76kWh = 18p per day = £68 per year
- 40 degrees wash - 0.77kWh = 8p per wash = £8.50 per year
- 60 degrees wash - 1.39kWh = 15p per wash = £15 per year
- 45 minutes walking on the treadmill - 0.21kWh = 2.2p
- Boil 1.7 litres of cold water - 0.19kWh = 2p
- Boil minimum level of cold water - 0.04kWh = 0.4p
- Toast 2 slices of bread - 0.04kWh = 0.4p
- 24hrs Sky+ on standby - 0.31kWh = 3.3p per day = £12 per year
When you have a complete list, you’ll be able to see from a glance where savings are to be made.
Don’t worry about things like the kettle / toaster drawing 3000 watts, the higher the power usage the quicker they boil the water / burn the toast. Other makes of kettle may draw half the power but they’ll need to be on for twice as long.
If you have found the results from using the plug-in monitor interesting then you’ll probably like The Owl Wireless Monitor. This monitor is different from the plug-in type as it shows the electrical consumption for the whole house on an attractive wireless LCD display. The Plug-in monitor is often used to determine the consumption of electrical items then put into a draw for occasional use, but The Owl is a monitor you’ll use daily for the foreseeable future. It’s a great conversation piece too!
Feedback
Feel free to ask any questions below or let us know any readings you find that surprise you.
January 14th, 2008 at 11:25 am
A very useful piece of kit. Am now considering the Owl
January 14th, 2008 at 3:07 pm
Good article. I was in a business where even a small production unit used about 65 million kWh/year, but even I’m complacent when it comes to home energy.
Regards,
Ian
January 14th, 2008 at 3:25 pm
Thanks
I’m extremely pleased with the monitor - and we’re measuring away happily!
I wonder if you can help with a query.
My electricity bill quotes kWhs as well as kWh.
Can you tell me what the s stands for?
With thanks
Katherine
January 14th, 2008 at 3:38 pm
Hi Katherine.
I suspect the ’s’ on the end of kWhs is just plural as in “My bill says I’m paying 11p per kWh and I’ve used 400 kWhs this quarter”
I’m glad you are getting on well with the monitor.
Russ
March 4th, 2008 at 10:46 am
I have been using the Plug in Electricity Consumption Monitor on a freezer that we have in our garage. I had the monitor plugged in for 24 hours, but it only showed a time of about 8 hours over the 24 hour period. I then tried in again and it was left on for about 60 hours (as I was away). When I came back I took the readings and it showed 19.03hours, 2.36 watts, and a cost of 0.19 (unit cost is .083p). Why is this? I did zero the unit as described in the booklet. Is the consumption monitoring unit malfunctioning?. The first time I used it on another freezer it was fine. Can you help to explain this.
Ta. Terry
March 10th, 2008 at 3:27 pm
Very interesting reading I found it while trying to find out how much it costs to run 4 cctv cameras which record onto our tv for 24 hrs a day. Can you help me with this please?
March 10th, 2008 at 5:08 pm
Hi Lesley.
You would need to use the ‘cumulative mode’ to measure how much electricity each component in your system uses over 24hrs then add them all together to get a total for the whole system for 24hrs.
For each of the video recorder, cctv cameras you would:
1) Plug the device into the electricity monitor.
2) Select the ‘cumulative’ mode
3) Zero the monitor
4) Let it run for 24hrs
5) Take the reading of the number of kwh’s used
Obviously, if all 4 cctv cameras are the same you would just measure one of them over 24hrs the multiply by 4.
Hope that helps.
Russ
March 23rd, 2008 at 6:50 pm
I discovered your site last Sunday using MSN while searching for need treadmill ratings. The post regarding The Green Kitchen - The Year of the Fridge was very helpful. Just wanted to say thanks!
March 28th, 2008 at 8:46 pm
Great site, good level of info, enough detail to keep interest whilst still being punchy and direct. I have added you to favourites and will drop in from time to time. Idea for future article: ‘The Green Hi-Fi set-up’, to look at pros/cons of seperates v. systems, including surround sound, wireless, headphones etc ? Thanks, keep up the good work. This is a subjct the whole planet needs to be thinking about. B
May 26th, 2008 at 9:48 pm
Can anyone help please?!
I’ve just moved house & inherited a pond in the garden. A friend has cleaned it out & installed a new filter/pump, but I am concerned how much this will cost me to run, as the instructions suggest it should be left on 24 hours per day. The manual states that power consumption is 11W and my electricity cost is £0.010329. I am really lost - i’ve searched the net, and have worked out costs ranging from £8 per month to £800 per month!! They all seem to contradict each other. Can anyone explain how I work this out correctly & more importantly let let me know their cost estimate for running this. Thank you so much. Brian
May 27th, 2008 at 9:50 am
Hi Brian,
If you look on your electricity bill you will see the cost per Kilowatt Hour (kWh). Broadly, this will be somewhere between 10p and 20p per kWh (2008 prices) depending on how good a deal you have / capped rates etc.
I’d guess that when you say your electricity cost is £0.010329 you might have a extra ‘0′ in there and you mean £0.10329 which would be just over 10p per kWh (not a bad price for 2008).
To keep things simple, we’ll go with 10p per kWh.
One kWh is:
- 1000 watts for 1 hour
OR
- 100 watts for 10 hours
OR
-10 watts for 100 hours
etc
So, roughly speaking, the following will all use one kWh and cost you 10p:
- 1000w Vacuum cleaner used for 1 hour
- 100w bulb left on for 10 hours
- 10w pond pump left on for 100 hours
As there are about 730 hours in a month, at 10p per 100 hours, your pond pump will cost 73p to run for a month. Probably less than you expect !
Using your exact figures of 10.329p and 11w gives:
730 / 1000 * 11 * 10.329 = 83 pence per month.
It’s worth noting that 11 watts is 11 watts whether it be a pond pump or an electricity saving lightbulb, so, at your prices, a 11w energy saving bulb will also cost 83 pence per month to run - which is why they are so desirable when trying to cut costs.
If your pond pump really is 11 watts then it’s not a big factor in your electricity bill, but, are you sure it’s only 11 watts ?
Looking around the web, http://www.pondpumpsdirect.com has 4 categories for pond pumps:
Heavy Duty Pumps: Between 280 watts and 2200 watts
Fountain Pumps: Between 47 and 135 watts
Filter Pumps: Between 28 watts and 450 watts
Low Voltage: Between 24 and 30 watts
Hope that helps.
Russ
May 27th, 2008 at 12:47 pm
Thanks Russ,
Your response is really appreciated.
As you’ve suspected, the pump is actually more than 11 watts. I double checked when I read you email and in actual fact it is the filter that is 11w, the pump that goes with it is actually 80w. Reading the literature, 80w is less than normal as it is a new Eco system. Therefore, I would presumably need to do the calculation based on 91watts. Therefore, if my maths is correct:
730 / 1000 * 91 * 10.329 = £6.86 per month
I’m hoping my simple logic is correct?
Great site - very informative & helpful - i’ve got it bookmarked now!
Thanks again,
Brian
May 27th, 2008 at 1:02 pm
Hi Brian,
91 watts * 730 hours = 66,430 watt Hours per month
= 66.43 kilowatt Hours (kWh) per month
At 10.329 pence per kWh, that’s £6.86
Spot On!
Remember they will probably charge you 5% VAT on top of this.
It’s when you multiply the monthly cost by 12 to get not far off £100 per year things become interesting.
Russ
June 5th, 2008 at 11:10 am
Hi!
I find this site very useful and thought-provoking.
I definitely need a plug-in and perhaps a wireless but first I have a couple of Q’s…
Wireles monitor clips to wire from my meter - any wire or a specific wire? (My meter has a half-dozen boxes all inter-connected with thick-ish grey cables/wires and some thinner green/yellow wires It’s a 200 yr old house)
Also, my supplier doesn’t list kWhs on my bill - they use the term ‘units’. But as my meter states kWh on the display and the readings tally I’m guessing that the terms are interchangeable?
I would appreciate your comments.
June 5th, 2008 at 12:59 pm
Hi Paul,
I suspect the meter would work with any of the thick grey wires - it’s knowing whats running through them that’s the problem. The wireless monitors generally work with any single-core wire of 12mm diameter or less.
With all those wires & meters, is it possible you have 3 phase electricity ? (in which case you would need 2 additional sensors for the wireless units).
Generally, the term unit relates to kWh for electricity. If each unit costs somewhere between about 10p and 20p (2008 prices) then it will be cost per kWh.
Russ
June 5th, 2008 at 2:16 pm
Hi Russ.
I don’t understand what you mean by ‘3 phase electricity’.
The boxes appear to be:
1) Where elec comes into house - from this two grey wires into…
2) Meter - from this two (same two?) grey wires plus another grey wire out into…
3) (Indeterminate) Black Box from which various wires into what apear to be FOUR fuse boxes! At least they all have a big red switch with ON written.
The meter reader is only ever concerned with box no2 - this displays Normal and Low rate usages. As I say - it has 2 wires in and 3 out.
Paul
June 5th, 2008 at 3:11 pm
Hi Paul,
Forget about 3 phase. From what you describe you don’t have it.
Box 1 - If you can manage to fit the sensor around the cable before it splits into 2 grey wires then that’s ideal (sensors will take 12mm max diameter). Otherwise, it’s likely that fitting the sensor around one of the 2 grey wires will give you what you want.
Worst case scenario would be that you would need to buy an extra sensor to monitor the combined consumption of the 2 grey wires from box 1.
From what you describe, a wireless monitor will work but might take a little bit more fiddling about than in a brand new house.
Russ
June 9th, 2008 at 9:48 am
Hi Russ,
Thanks for the advice.
By the time you read this I will have placed my order for a plug-in - with this we will be able to start monitoring/saving immediately (and I have some doubts about the efficiency and usefulness of an old fridge/freezer we’re currently running!)
I will forego the purchase of a wireless for now - I’m going to get an electrician to look at my ‘Spaghetti Junction box’ and advise me exactly what each box/component is for.
Can you advise on bulbs? We have four chandelier fittings:
2 take 5 x 20W candle bulbs and are operated by dimmer switches
1 takes 2 candle bulds non-dimmer switch and…
the last takes 15 x 20W candle bulbs operated by an industrial-strength dimmer switch.
I would like to change to energy efficient bulbs. Are there any such candle bulbs?
Paul.
June 9th, 2008 at 12:22 pm
Hi Paul,
The problem I can see with using energy saving bulbs in a chandelier is that they might not look very good. Energy Saving Bulbs are bigger than filament bulbs, most cannot be dimmed and they won’t give out the sort of light that would compliment a chandelier.
Personally, I would keep the chandelier bulbs as they are for use on special occasions and find some other form of energy efficient lighting for everyday use.
Before you splash out on 27 energy saving bulbs, buy 1 just to make you you like it..
Russ
June 10th, 2008 at 10:28 am
Hi Russ,
I just hope someone starts making suitable energy saving candle bulbs before incandescants are phased out! Otherwise, a lot of people are going to have to change their light fittings!
Paul
June 13th, 2008 at 1:22 pm
Im currently checking my electricity usage with a monitor, I reckon my usage will be less than what is claimed on my electricity meter, is there anything we can do if we reckon our meter is given out inflated readings?
June 13th, 2008 at 1:47 pm
Hi Micky,
If you suspect your meter is wrong you can ask the electricity board to come out to you and test it. I believe that if your meter is within 5% either way of true they will leave it be, otherwise they will replace it. I’m told it’s rare for a meter to be defective.
Russ
July 2nd, 2008 at 5:23 pm
Hello,
I’m looking for a way to separately meter the electric usage of three rooms. (with a view to splitting the electric bill equitably in a shared housed). Would plug in monitors be suitable for this, (one for each room)? I would need the monitors to track and remember usage for about a month at a time - is this possible, i.e. does the device remember readings while it is powered off and start cumulating again when the power comes back.
regards,
Tom.
July 3rd, 2008 at 11:45 am
can you tell me on a domestic freezer when I open the door how much energy am I losing and how long it takes to get the temp back to normal regards ken chandler
July 4th, 2008 at 12:58 pm
Hi Tom,
I have a Plug-in monitor in my kitchen that I leave the kettle plugged into. It happily sits there week in week out adding up how many kWh’s I use.
It has a battery backup so power cuts wouldn’t be a problem.
If all the occupants of the rooms were to use a 6-way extension lead plugged into the monitor then I guess the monitor would give a good indication of how to split the bill. It won’t of course take into account lighting or anything else that wouldn’t take it’s supply through the monitor.
Russ
July 4th, 2008 at 1:12 pm
Hi Ken,
I assume you mean an upright freezer rather than a chest freezer ?
I think both answers depend on what’s inside the domestic freezer.
Modern upright freezers have slide draws that are great for minimising temperature loss as the cool air stays trapped in the draws rather than draining from the freezer and being replaced by warm air.
It will take a lot less time & energy to get a freezer with draws back up to temp.
I had a look around your web site - I’m sure the “space invaders” would help …
Russ
July 28th, 2008 at 3:44 pm
Hi
I have just found your web-site and found it very helpful. We are really keen to try to control our energy use and would like an energy monitor. I will order the plug-in one but ultimately the Owl would probably be the most useful gadget. The trouble is that we tried one from B&Q but found that there was not enough space around the thick mains electricity wires to get the clip around them and there is virtually no play in the wires. Is there an alternative monitor that would work or can you suggest a way of getting the Owl connected?
Carolyn
July 29th, 2008 at 12:28 pm
Hi Carolyn,
All of the wireless monitors I’m aware of have very similar clips that need to be fixed around the main supply wire. However, some of the fitting instructions are too restrictive to keep things simple. In practice, we have found that the clip can be fixed around the wire either before or after the meter and also the clip can be fitted to either the red (+ve) or black (-ve) wires.
I’ve yet to find a meter that it wasn’t possible to fit a clip around somewhere.
If you would like to email us a digital photo of your meter and wiring we would be happy to let you know our thoughts on your system.
Russ
August 3rd, 2008 at 12:00 pm
Hi
using a Owl monitor I would assume that providing there is access to cables from the consumer unit and you could identify what cables are what. You would be able to monitor what power a ring individual ring main or radial circuit is using.
August 4th, 2008 at 8:30 am
Hi Paul,
If you can locate a single core wire for a ring main, then yes.
The sensors measure the EM field generated by the current flow, which is why the sensors must be fitted around a single core wire.
If you were to place the sensor around a 2 or 3 core wire e.g. the flexible cable to the kettle, the wireless monitor would read zero because the +ve and -ve fields cancel each other out.
Russ
August 15th, 2008 at 3:54 pm
I was reading the blog on refrigerators and freezers, I recently purchased a product / device, called the refrigeratorsaver, it looked simple but to simple for what it is and how you have no installation at all.
But I must say this little device which is infact a food tempreature thermometer, has really helped me get my produce at the correct tempreature, which has made the produce last longer as it isn’t cooling to cold, I made the adjustment on the thermostat as explained, and I have been able to reduce the tempreature by 3 clicks on my thermostat dial, this is obviously energy savings, but I amsure it want show on my electricity bill.
Worth taking a peak though, http://www.refrigeratorsaver.com
August 15th, 2008 at 9:32 pm
Hi
I have a Scandnova upright frost free freezer which seems as if it is using electricity for 23 hours out of 24, consuming a good 6/7 units. It is 4 years old and I cannot find out who made these machines to raise this matter with them. Can anyone help.
August 26th, 2008 at 10:54 am
Just wanted to say THANX the suggestions I found on you web site are brilliant !!!
Giovanna of http://energysave.altervista.org/
September 17th, 2008 at 9:06 pm
Found your website, as have had some concerns re the consumption of our chest freezer….or rather the elder of the two. It seems to be making a noise much of the time, whereas the other slightly younger model is relatively quiet. Neither are young; the older is at least 25 years old! We grow our own vegs and fruit, thus the need for 2 large freezers. During two recent absences from home, one of 5 days, the other of 12, we took a note of the meter readings before leaving, and again on our return. The freezers and a fridge-5years old- were the only gadgets switched on, other than the burglar alarm.
On both occasions, we used 0.266 Kwh per hour, ie 6.38Kw per 24 hours. Should we be concerned?? Our electricity is paid by direct debit, at £81 per month. Just the 2 of us in a 4-bed 3-public rooms, now the kids have gone. Only to be replaced by grandchildren, still at the c-beebies stage….Thanks
September 23rd, 2008 at 3:11 pm
Hi John,
I think it would be a mistake to assume it’s just the fridges/freezers & burglar alarm on. There are always things you haven’t thought of that consume power.
The only real way to get a reliable indicator to whether a fridge/freezer should be replaced is to accurately measure the electricity consumed over 24hrs using the plug-in type of electricity monitor and compare this figure to manufacturers figures for modern A / A+ rated items.
Good Luck.
Russ
November 1st, 2008 at 4:03 pm
I am hoping to fit remote socket switches to power off my Tv, TOPbox, dvd all into a 4gang ext. If I fit The monitor in between the socket and ext. plug will this work, so I can monitor all the consumption of the collective sets.
This I hope to repeat with my PC and all the printers and scanners etc.
November 2nd, 2008 at 9:02 am
Hi James,
That would be fine.
Russ