I was listening to the radio about rising energy bills then I had my breakfast. This got me thinking.
I have a combi boiler. I intend to turn the heating off for the summer. Without the heating, the hot water seems to take longer to arrive wasting a lot of water and presumably gas. Would it be more efficient to boil a kettle for the washing up?
Yes, I do similar.
Gas or electric to heat the kettle?
As pointed out in another thread you will still be paying the daily standing charge even if you are not using any gas
A lot of advice on social media recently suggests to make a cup of tea boiling a cup of water in the microwave is the cheapest followed by a gas kettle then the electric kettle.
I did a one off test by boiling 3 pints of water in each Microwave = 5p Gas (water in a large pan fully covering the burners) = 4.6p Electric kettle = 5.4p
Notes: My Microwave is also a fan oven/grill and after a short period of microwaving the fan turns on and stays on for a short period afterwards so an extra cost for the fan.
The electric was measured with a cheap plug in power meter that can display kWh to 3 decimal places although this resolution is unlikely to be reflected in it's accuracy.
The gas consumption was taken from readings from my smart gas meter (reading taken before and after the test). The gas meter reads to 3 decimal places for cubic metres.
The electric kettle automatically switches off once the water is boiling whereas gas requires intervention so if you are not standing over it you may incur extra costs.
I came to the conclusion not worth the hassle trying to save a penny a day making cups of coffee or tea so I've stuck with the electric kettle.
Yesterday BG was suggesting that the microwave is a vampire device and should be switched off at the mains when not in use. My power meter shows 0.0W when not in use, and 22.3W when the door is opened and the light comes on.
For washing up you may be able to use cold water and detergent for items that are not greasy.
Electricity, but I could use gas.
This is true, but the same applies to electricity.
This seems to be fairly marginal. However, it's not three pints. The tap has to run for a considerable time before the water from the combi reaches operating temperature. That is the diseconomy that I am asking about.
If you're on a water meter, the c.1p litre will soon start to add up if you're drawing say 5 litres of water several times a day just to get to the hot water and wash your hands . . .
I tend to use the electric shower over the bath for a quick wash. I've a combi boiler and small amounts of hot water - even with the preheat - is the single worst part of it. Baths and showers are great though.
We are not on a water meter (Scotland). My question was about the cost of heating the water, not the cost of the water.
Ah right, good. You did mention wasting a lot of water and you asked about efficiency - hence the post.
it could depend on which one I have a few at hand and a brennstuhl one I've had a few years gives quite differnt reading from another couple I have tried and bought last year. I was testing the power consumpion of PCs on standby and thought 17 Watts was quite high compared to my home iMac which was about 1 watt. I just happened to bring my meter from home to work and foudn that my one measured about 1 watt for the PCs whereas the work meter measured it as 17W , so I bought another one for work which was much better and closer to 1 watt than 17W. I know computers are different in their VAR.
Pity you didn't quote what time it took to boil too, as I've found microwave oven to be pretty slow to heat water in any more than a mug full of water. Plus the extra danger where as cup handle also gets very hot. Usually I only need to boil a cup full certainly not 3 pints at a time.
I think they are exaggerating these vampire devices as a smokescreen for making huge profits. Maybe cheap phone chargers might be a few watts. But things like hubs and routers and TiVos might be 5-10 watts but it's still minimal unless you have dozens running.
There is a EU law, which we adopted, that says new electronic equipment or white goods? now must be < 1W in standby. My PVR has two standby modes designated standby and deep standby and it's only the latter that is around 0.5W. It still wakes up from deep standby for a recording.
Those figure for microwave and electric kettle heating seem strange unless the microwave has a power factor which affects the reading of the power meter. An electric kettle is basically 100% efficient (there will be mainly convection losses of heat though the kettle body. Is the body of your kettle metal? That will be the most inefficient on retaining heat, but a glass or plastic-bodied kettle won't be anywhere near as bad).
According to this "Scientific American" 2009 paper at
And from a question to
"A microwave is about 50 percent efficient. Most of the energy is lost in the process of converting electricity to microwaves (which are part of the electromagnetic spectrum).
An electric stovetop is about 70 percent efficient, although that varies widely depending on the type of pot or kettle you use. Most of the energy is lost heating the air around the stove.
An electric teakettle is about 80 percent efficient, although again this varies from kettle to kettle. Electric kettles are generally very well insulated, and the heating coils sit directly in the water, so less heat is lost to the air."
It continued: "Our question asker, Ben, ran a mini-experiment in his own kitchen. He set up a current-meter on an electric tea kettle, a microwave, and an induction hot plate and timed how long it took each to bring 500 mL to a boil. The results came close Williams? estimates: The microwave was 34 percent efficient, the electric teakettle 71 percent efficient, and the induction hotplate 83 percent efficient."
Sorry, badly worded on my part. I was using the loss of warm water as evidence of wasted energy.
Transformer based or inverter?
(if that latter, and your power meter is not true RMS that could cause a low reading)
I am surprised that a microwave would be cheaper than an electric kettle.
I don't get that with my mugs and always use the microwave.
The reason for that in the real world is that when you are producing a single cup full of hot water, there is no wasted hot water with the microwave, but is maybe even a couple of cups of hot water wasted with an electric kettle because of how the element is done.
Alan's test with 3 pints isn't a good measure with a cup of hot water.
That's sort of what I was suggesting my Tivo, TV and hub/router are all on the same extention block and at worst it''s probably 5W but not easy to measure, my 27" iMac flickers bewteen 0, 1,2, watts So I don;t think modern devices on standby or sleep will make much differnce if unplugged Think I'm more likely to strain my back bending down to unplug them. .
But here in my lab there are 100 PCs, which is why we bought two new power meters, depending on which one we used on a 24" dell PC 7460 AIO when in sleep mode 7-21W : 0-2W : 0-5W watching the display for about 10 seconds. shutdown 7-12W : 0W : 0W with login window prompt 38-41W : 36-46W : 34-37W which are on 24/7 (even though no on uses them after 6pm or before 9am, or sat and sun) Presently they can't be put into sleep mode either and are left in login window mode So if I were paying the electric bill for the lab I'd unplug all the PCS. well actually I'd hit the emergency breaker cut out power for the whole lab, which is what we do over the christmas holidays.
You are correct. I've just repeated the microwave and kettle tests. The electric kettle results are similar to before but I must have misread or done something else wrong with the microwave.
Plastic walled kettle 3 pints or 1.7l = 0.190 kWh (14C to 100C)
Microwave 0.400 kWh taking a few seconds under 20 minutes to heat 14C to
98C. Both fan and light were on 38W for 20 minutes. Both were heating the oven cavity but the fan was blowing air around the cavity and around the open toped glass container.
Those "deep" standby modes are often unusable as they don't pass the aerial signal through to the next device in the chain. Unless you have such a strong signal you can use a passive splitter.
Mine has a clock and is about 10W, but there's an 'eco' button that turns off the clock and then there's no detectable W or VA. I've 2 clocks in the kitchen each of which will run for over a years on an AA cell - I don't need a 10W one.
The one that always annoys me is the sort of figure they quote for leaving the TV on standby. Our living-room TV is a few years old now, but takes less than 0.2W on standby. So for, say, 20 hours of standby a day, at 28p per unit, that's less than 41p per year. I think I'll put up with the cost for the convenience of not having to switch it on at the socket and wait for it to "boot" up each time.
But British Gas "research" says £24.61 for the TV! However, their figures have been heavily criticised as the 2013 EU legislation requires less than 0.5W in standby giving an annual cost of around £1.30.
Its a similar story with their other equipment figures and their well publicised vampire annual costs of £147 may also be 20x too high.
Much better to get a smart meter* and achieve those massive savings promised in the early adverts :)
*Since the demise of Avro I'm now with Octopus and they appear to be having trouble changing the displayed tariff for the remote smart meter display module (and presumably the calculated ongoing usage costs). It appears that customers are on either on one of two update methods and one method isn't working, and they are aware of the problem. So much for the benefits of smart meter in monitoring the usage costs :) It doesn't bother me because I'm aware of the problem but I do wonder if those with fuel poverty are being mislead by the smart meter still programmed with pre-April tariff information. Note: My smart meters have been installed since being moved to Octopus.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.