Misleading statement by Martin Lewis on microwaves

One-Eye

Martin said "If you had a 1000W microwave and you put it on for 10 minutes, one KWH for a sixth of an hour, a sixth of 34p is about 6p, shall we say? So it's 6p turning the microwave on for that amount of time."

This was apparently on Martin's recent podcast and has been reported in many newspapers eg. https://www.mirror.co.uk/money/martin-lewis-word-warning-anybody-28668777

Martin should realise that the 1000W is the "output power" or the "cooking power". The average efficiency of a microwave is about 71%, so the input power of a 1000W microwave is 1400W. 10 minutes usage would use 0.233kWh and at 34p/kWh this would cost about 8p.

Appliance efficiency can vary, but the average consumption is in the table below.

(My cheap 800W microwave uses 1200W - measured with a digital power consumption meter plug)

MikeJXE

It could be a typo, typing mistakes they happen on here all the time, I'm sure we have all seen them and treated them as such and worked out what was meant, except for the ones who have to point them out 

stewie_griffin

It might be a typo (I suspect it’s more a misunderstanding of how microwaves work), but it still makes the article misleading.

elsien

Just as a general comment, if I need to cook then I cook. Whether it costs me 6p or 10p doesn’t really go onto my radar. I might use the slow cooker rather than the oven for things that take longer, or eat meals that are quicker to make like stir fries, but how many people seriously want to know to the penny how much each cooking appliances cost?

Spoonie_Turtle

elsien said:

Just as a general comment, if I need to cook then I cook. Whether it costs me 6p or 10p doesn’t really go onto my radar. I might use the slow cooker rather than the oven for things that take longer, or eat meals that are quicker to make like stir fries, but how many people seriously want to know to the penny how much each cooking appliances cost?

I think it's really only relevant to people who need to know, and to people who don't need to but like to keep track because they're interested (in which case they'll be using energy monitors anyway).

MikeJXE

My energy monitor states my microwave cost 60p an hour, seeing as it's only used for breakfast bacon 2m minutes 40 seconds beans 1m 40 seconds and egg 1m 10 seconds it would make very little difference what size microwave it was 

BUFF

& my 1000kW microwave doesn't run at full power all the time - it does it in pulses.
I suspect that there is enough variability that there is not going to be 1 answer that is correct for all & I am not going to get upset with somebody for a ~2p error..

ariarnia

i agree. i think the point martin was making was that the number (600w-1000w) sounds a lot. so people might be put off using it and think the hob is a cheaper way to heat soup or whatever. but its actually pennies to use for a lot of things. 

facade

ariarnia said:

i agree. i think the point martin was making was that the number (600w-1000w) sounds a lot. so people might be put off using it and think the hob is a cheaper way to heat soup or whatever. but its actually pennies to use for a lot of things. 

There are a lot of statements about, some in technical magazines that really should know better.  The sentiment is correct, but they could at least check if their figures are right.

In my PC magazine, last month they suggested that an electric kettle uses 1000 times the energy of an LED bulb (they must live in the dark if they only have 3W lights), and that an 80% efficient computer power supply can only give out 80% of the rated power, rather than the power given out is 80% of the input power. 

stewie_griffin

3W LED lightbulbs aren’t uncommon. I think they produce about 270 lumens.

Mstty

facade said:

ariarnia said:

i agree. i think the point martin was making was that the number (600w-1000w) sounds a lot. so people might be put off using it and think the hob is a cheaper way to heat soup or whatever. but its actually pennies to use for a lot of things. 

There are a lot of statements about, some in technical magazines that really should know better.  The sentiment is correct, but they could at least check if their figures are right.

In my PC magazine, last month they suggested that an electric kettle uses 1000 times the energy of an LED bulb (they must live in the dark if they only have 3W lights), and that an 80% efficient computer power supply can only give out 80% of the rated power, rather than the power given out is 80% of the input power. 

I think you can get to over 30w equivalent from a 3w led bulb these days. Most can live with 40w so a couple of lamps running these is good for a cozy night.