# Hourly usage on specific items

• 17-04-19, 18:28
Smk1970
Hourly usage on specific items
Hi. How would I work out how much it costs to leave a TV on standby or a light bulb on?
• 17-04-19, 19:09
woz
Hi smk1970
it depends on whether you use the manufacturer’s quoted power consumption or you actually measure it yourself. You may find the two differ especially on cheaper light bulbs.

Using a 12 watt, a 60 watt light bulb and a TV quoted as taking 1 watt on standby as an example
multiply the wattage by the number of hours per day in use let’s call it 8 hours
lamp 12 watt x 8hrs = 96 watt hours
lamp 60watt x 8 hours = 480 watt hours (or Wh)
tv 1x 8 = 8 watt hours
then multiply that figure by the number of days in use, for example every day would be 365 days let’s assume 300 days
12W lamp 96x 300 = 28,800 Wh
60W lamp 480x 300= 144000 Wh
1W tv 8x300= 2400 Wh
divide Wh by 1000 to get kWh
multiply that by your KWh rate which is on your statement (don’t forget to add vat at 5% if the rate is quoted exc vat)
Lets day your rate is 15p a kWh inc vat
12W lamp will cost 28.8x15p=£4.32
60W lamp will cost 144x15p=£21.60
tv cost 2.4x15p=£0.36
Or to put it another way, every watt costs 8.76 x 15p (or your rate per kWh) if used for 24 hours 365 days

The examples used above are not meant to be an accurate guess as to what your actual devices use, I used a range to illustrate. My old tv used over 2W in standby, the newer one less, but I don't leave anything in standby apart from essentials like routers. It's not practical to switch certain things off as much as I'd like to....
• 17-04-19, 19:17
talldave
Modern TVs use so little in standby (mine uses 0.1W) that it can take thousands of hours before you even use a unit (1kWh) of electricity. For the lightbulb divide 1000 by the wattage and that's how many hours it takes to use a unit of electricity (e.g. a 10W bulb takes 100 hours to use a unit). That unit costs 14.333p, so a bit more dividing will give the cost per hour.

EU regs limit TVs to 0.5W in standy, assuming they're not recording/streaming.

Manufacturer product sheets often quote standby consumption. My microwave uses 7W, that's 70 times what the TV uses! My wifi repeaters use about the same but they're a bit more useful.
• 17-04-19, 20:04
Gray4276
Quote:

Originally Posted by talldave
Manufacturer product sheets often quote standby consumption. My microwave uses 7W, that's 70 times what the TV uses! My wifi repeaters use about the same but they're a bit more useful.

Now that's not somesomething you would expect..........a microwave using 7W on standby !!! I'm going to unplug mine when not in use from now on.
The best electrical saving I've made in the last year is replacing every single light bulb in my house for LED (I was willing to take the "hit" of purchase price) the only bulbs that are filament bulbs are the fridge and the oven. Changing from "ordinary" bulbs to LED is the biggest and easiest saving that you can do to a normal domestic home........I recommend this to everyone. 💡📉 😇
• 17-04-19, 21:24
woz
How did you measure the microwave? Mine has the worst power factor (not power consumption) of any device I've ever measured.
Quote:

Originally Posted by talldave
Modern TVs use so little in standby (mine uses 0.1W) that it can take thousands of hours before you even use a unit (1kWh) of electricity. For the lightbulb divide 1000 by the wattage and that's how many hours it takes to use a unit of electricity (e.g. a 10W bulb takes 100 hours to use a unit). That unit costs 14.333p, so a bit more dividing will give the cost per hour.

EU regs limit TVs to 0.5W in standy, assuming they're not recording/streaming.

Manufacturer product sheets often quote standby consumption. My microwave uses 7W, that's 70 times what the TV uses! My wifi repeaters use about the same but they're a bit more useful.

• 17-04-19, 21:31
talldave
Cheap crap microwave = sloppy energy hungry design!

I agree LED lights are the big gain. About 10 years ago my best find was a treadmill that used 40W when "off". I hate "touch" lamps due to 24/7 consumption.

Sadly I'm renting at the moment so can't do much to reduce the base load (e.g. elderly burglar alarm) - it's 77W at its lowest. And the boiler/pump uses nearly 100W when on and being a single glazed place it's on a lot:-(.

If you have a flashing LED meter I recommend the Geo Minim energy meter to get a very accurate "whole house" consumption figure. They do a clip-on version too but I find clip-on meters a bit crap at low consumption levels.

- - - Updated - - -

Quote:

Originally Posted by woz
How did you measure the microwave? Mine has the worst power factor (not power consumption) of any device I've ever measured.

The figure came from the spec sheet but confirmed by checking the drop on my Geo Minim LED when turning it off.
• 17-04-19, 22:14
woz
Mine is a Panasonic, so expensive crap, but I measured using an accurate expensive meter, it was a while ago but I remember it had a power factor that was ridiculously low (I didn't look at the waveform it may have been laced with harmonics.)
7W sounds high to me, but I suppose it's possible, I'll re-check mine as soon as I can and see if I get the same answer as I have a newer meter.
If you look at the online specs of the 2018 Panasonic microwaves the popular ones that are quoted (not all are- I wonder why?) the standby is quoted as 0.7 or 0.8W

People don't understand the difference between reactive power and true power (you don't pay for the reactive part but your energy generator does)
Clamp sensor power meters are notoriously inaccurate at low power, you simply can't measure anything under 50W with any reliability.
Also I don't think they can discriminate poor power factor but I'm not sure...when I get some time I'll test against my mew meter)
Of course the geo gets round that issue by measuring the pulses at the meter. I have no idea how reliable that is at very low power, you'd have to make sure everything else was absolutely constant and check over a long period to know.
Quote:

Originally Posted by talldave
Cheap crap microwave = sloppy energy hungry design!

I agree LED lights are the big gain. About 10 years ago my best find was a treadmill that used 40W when "off". I hate "touch" lamps due to 24/7 consumption.

Sadly I'm renting at the moment so can't do much to reduce the base load (e.g. elderly burglar alarm) - it's 77W at its lowest. And the boiler/pump uses nearly 100W when on and being a single glazed place it's on a lot:-(.

If you have a flashing LED meter I recommend the Geo Minim energy meter to get a very accurate "whole house" consumption figure. They do a clip-on version too but I find clip-on meters a bit crap at low consumption levels.

- - - Updated - - -

The figure came from the spec sheet but confirmed by checking the drop on my Geo Minim LED when turning it off.

• 17-04-19, 22:59
talldave
Using LED pulses makes it accurate at all levels of power consumption. Since it's timing between pulses, if there is going to be any accuracy variation it's likely to be most accurate at the lowest consumption.

With a reasonable house losd running (200-300W), switching one appliance off gives a drop within seconds on the meter.
• 18-04-19, 00:10
woz
I agree but my point was that in order to measure a very low power device the pulses would be a longer time apart and you'd have to be sure that during that time period there was no variation in use from anything else.
Quote:

Originally Posted by talldave
Using LED pulses makes it accurate at all levels of power consumption. Since it's timing between pulses, if there is going to be any accuracy variation it's likely to be most accurate at the lowest consumption.

With a reasonable house losd running (200-300W), switching one appliance off gives a drop within seconds on the meter.

• 18-04-19, 00:59
talldave
Quote:

Originally Posted by woz
I agree but my point was that in order to measure a very low power device the pulses would be a longer time apart and you'd have to be sure that during that time period there was no variation in use from anything else.

Yes it's a bit hit and miss with things that are only a few watts. But if the house consumption is high at the time you test, the drop in reading is quick. And it's easy to repeat several times to verify. My main problem when having a play was the heating cycling through its various states of power consumption!

Having to use a wifi mesh network in addition to a router is a consumption pain - damned thick walls! At least my powerline sockets drop to low power when idle.
• 18-04-19, 12:02
Gray4276
Hi Woz & Talldave,
Really interesting stuff from both of you......can you provide details of the meters that you are using and recommendations where to purchase please.
• 18-04-19, 15:31
woz
I'm using an old OWL and it's a clamp type - don't bother, too unreliable, (at the low end as clamp type) flaky firmware, no support from OWL , but OK when higher power devices are on.
Sometimes I have to read between the lines...
If I was buying again I'd go for the pulse counter type, geo minim+ if you have a flashing light on the meter, which begs the question do Smart meters have a flashing light?
On the other hand if relations with the rest of the family are good just switch stuff off...
Doing that has the benefit of generating much heat in our house but it's the wrong type of heat...
Quote:

Originally Posted by Gray4276
Hi Woz & Talldave,
Really interesting stuff from both of you......can you provide details of the meters that you are using and recommendations where to purchase please.

• 18-04-19, 17:08
talldave
Quote:

Originally Posted by Gray4276
Hi Woz & Talldave,
Really interesting stuff from both of you......can you provide details of the meters that you are using and recommendations where to purchase please.

I'm using Geo Minim+ LED, £39.95. Needs a meter with pulsing LED. My transmitter was faulty on delivery, contacted Geo and replacement supplied next day delivery. Excellent customer service.

I used to use an original Wattson, but my ex got the Clip transmitter when we split :-(.
• 19-04-19, 12:45
woz
Cable it, I've the same issue and promised myself I'll get round to it one day...
Having to use a wifi mesh network in addition to a router is a consumption pain - damned thick walls! At least my powerline sockets drop to low power when idle.[/QUOTE]
• 19-04-19, 14:26
talldave
Quote:

Originally Posted by woz
Cable it, I've the same issue and promised myself I'll get round to it one day...

Rented property so not touching anything, but copper is best and doesn't need a reboot.

Tablets/phones will always need wifi anyway.

Powerline is great, but master socket crashes every week or two.

BT Whole Home wifi great, especially with latest firmware, but master disc crashed this weeks after 5-6 weeks of smooth running.
• 20-04-19, 17:31
Gray4276
I'm using Talk talk with their latest Router/Hub...... getting 70Mbps in room with router and about 40+ on opposite side of the house....and 20ish upstairs and not having to supplement with boosters. Really had to nag TT to get them to supply correct speeds.