What does it REALLY cost to run your energy guzzling household appliances? (Less than you think)




On another forum, I saw
a heartbreaking post from someone who told us they were going to give up
heating food to save money. Raw food only from now on.
This really brought me up short. I already
knew that many people are the wrong side of the breadline, with not enough
money to live on. However, I did feel that this post was based on not
understanding how much it costs to cook food, and this led me to think a lot
further about what it costs to run household appliances - especially what it
costs to cook food.
I want to know this in
order to be able to reassure people to whom pennies make a difference what it actually
costs to use their appliances.
So I started to do some maths. And I found
that virtually all the sites I found agreed with my maths. But here's the
kicker - WE WERE ALL WRONG. The wrong sites are still out there - sites
like How
Much Electricity Does a Slow Cooker Use in the UK? - Chef's Pick
(chefspick.co.uk)
So here are the questions. I want your help
with number 3, good people of MSE.
If you want to discuss questions 1 and 2, the floor is yours.
1. What was my maths?
2. Why was I wrong?
3. What are the real costs of running electrical
appliances - and let's focus on the ones used to heat food, as a starter?
4. Could MSE please do an article about this?
Happy to work with them….
I reserve the right to
add further questions!
QUESTION 1.
First I found out what a kilowatt hour costs. I thought that https://www.nimblefins.co.uk/average-cost-electricity-kwh... was a good listing, shows different regions
of the country, and looks pretty up to date. Let me know if you think I was
wrong. So I will use 29p as the cost of
a kWh. So far so good.
Then I looked at the wattage of the appliance I was
considering. For example, and let’s keep
it simple, a small slow cooker is 100w.
(A large one is about 1.7Kw)
So then I made my Big Mistake. ‘OK’, I
thought. If a SC (for example) is 100w, that means it
will use a Kw in 10 hours. (No-one is likely to use it for that long, but as I
said, let’s keep it simple.) So cooking
a stew in this little machine for 10 hours will cost a kWh – 29p. Job done.
QUESTION 2.
I WAS WRONG! I was actually
surprised that it cost that much, and rightly so.
If you listen to a slow cooker cooking (or a hob heating up, or an oven) you
can actually hear it switching itself on and off as the thermostat kicks
in. If it’s a gas oven, you can see the
flames adjusting their size. My 100w
slow cooker does not draw 100w consistently.
A simple model will just turn itself on and off to maintain the temperature and not overheat.
A 100w appliance will not draw more than 100w (ok, it may have a 10% tolerance)
so if it has a thermostat, it is obviously drawing a whole lot less than 100w
an hour. In fact, once the crockpot gets
up to temperature, it will draw hardly any energy – it just needs to maintain
that heat. (And yes, I appreciate that it might be a good idea to transfer the
pot to a hay box once it’s hot, and I will be passing on this idea too.)
Similar questions apply to the operation of an oven. Husband tells me – and it makes total sense –
that modern ovens use hardly any electricity once they get to temperature. (Ours displays a light when it is topping up
the temp, and this light is hardly ever on!)
I hardly like to mention the difficulties of costing gas consumption – I
think I would be happy to tell people that ‘modern, well insulated gas ovens
cost less’ once we’ve got a good figure for electricity, and leave it at that. But what does an oven actually cost to run for 30 minutes? 2 hours?
QUESTION 3.
So what is the real cost? Obviously I appreciate
this will vary. Even the kWh cost
varies, for heaven’s sake. And the start
temperature of the crockpot. And the
efficiency and insulation of the SC. But
I’m sure we can improve on telling people that a slow cooker costs 19p to 49p
to use, which is what the site listed above (and others) is/are telling people on current
prices.
A friend used a plug in power and energy monitor (PEM) on the kWh setting to
measure a 6 hour slow cook, and came up with results which suggested that what
the PEM was doing was actually taking the max wattage used and multiplying it by
the time the PEM was plugged into it. The same faulty maths, in fact. Husband (an electrical engineer) tells me that the kWh setting on these simple
machines is useless, and common sense would suggest he is (as ever!)
right. Using the wattage setting
suggests a far, far lower reading. When
we plugged in our SC the wattage reading was in low single figures initially –
the time when the reading would be relatively high, as this is when the pot itself
would be heating up.
I do remember that when SC were launched as a major product the advertising
blurb was that they cost about the same as a lightbulb. Even this seems high, frankly. Lightbulbs of the time were 100w, and
lightbulbs DO draw 100w consistently. SC
do not.
The only way I can tell of demonstrating the real cost (without spending lots
of money on specialist equipment) is to have a video recording of the PEM the
drawdown of watts over many hours, and then averaging this. Another, much simpler way, might be to ask
the SC manufacturers. Of course, they
want to sell SC, so are likely to give optimistic figures. But I thought this question was worth
discussing on here to see if I could get any helpful input.
Thank you for any helpful contributions, which I hope will help some people who
are really suffering from rising costs at the moment.
This signature was changed on 6.4.22. This is an experiment to see if anyone from MSE picks up on this comment.
Replies
So much to read, so little time.
This signature was changed on 6.4.22. This is an experiment to see if anyone from MSE picks up on this comment.
I have only just started doing this. Initial results: (I’ve got a fairly standard sized cooker with two ovens). Running the bigger of the two ovens for an hour at 170 degrees used 1.3 extra units. Running the smaller oven at 150 degrees for 35 minutes used 1 extra unit.
Tomorrow, the slow cooker!
I think most people who have been talking about boiling water and putting it in a flask have been people who have Economy 7 and therefore are taking advantage of boiling the kettle when the electric is cheaper than when they want to use the flask contents.
I think the point I'm trying to make is that although I was dubious, the smart meter has turned out to be a very useful & informative addition to our efforts to keep running costs as reasonable as they can be, given 6 adults in a leaky old house. Hopefully our usage will drop once the double-glazing's installed in a month or two, too, but we'll keep working on it!
So much to read, so little time.