Saving fuel, but wrong information given!

[ericmark]

I was looking at the BBC web site with "Use an air fryer or microwave instead of an oven" advice, giving details of cost of cooking a baked potato.
5p in a microwave (800W for 10 minutes)
26p in an air fryer (1000W for 45 minutes)
£1.02 in an oven (2000W for 90 minutes)
They all work out as on all the time with a cost of around 28p per kWh, but an oven will not be on for 90 minutes, it will be one for around 15 minutes then it will cycle on/off, where the microwave will be using the 800 watt for the whole of the 10 minutes, and I know when I put in a pair of baked potatoes it takes a lot longer than 10 minutes, and in the main they are part of a meal, so also have a pizza which will go in the oven.

So the question is does pre-cooking the pair of potatoes in the microwave for 10 minutes, then transferring them to the oven to complete the cooking, together with the pizza use more or less energy to switching oven on earlier and baking only in the oven? As oven will be used for pizza.

I can easy measure power used in the microwave, it plugs in, so can use plug in energy meters, but the oven is hard wired, so hard to measure. Also the oven has 3 elements, top, side and back, with a 12 position selector knob to select if rear fan, top grill or side elements are used.

So to cook for example bacon, I can use the large bottom oven and grill closed door, or top oven and grill open door, bottom one easier as only turn bacon once, but which uses more energy?

As to other items, drying outside only works if the cloths can then be worn, if they need re-washing because of bird lime or soot, not so sure? OK first house I had a car port, ideal for drying cloths, but I live in an estate, where most homes have the option of using solid fuel, and we have thankfully loads of wild life, I love to sit looking out of the window and watching the red kites flying.

Even a simple thing like using a dish washer, told it uses less hot water than hand washing, so cheaper than hand washing, but the programs range for 58 minutes to nearly 3 hours, same with washing machine, both have so many options and very aware each wash uses one tablet, be it long or short wash, so one does not want to rewash, but one does want to wash for as little as possible. And every wash is different.

So things like switch to LED lights, not so sure either, I had moved to fluorescent years ago, why they compare with tungsten I don't know, seems daft, who uses tungsten? I am sure the compact fluorescent uses more power to a LED, but as a tube, not so sure, both around the 95 lumen per watt.

Take control of your central heating it says, I have around 16 thermostats in my home, two on the wall, 14 on the radiators, of them one wall thermostat is programmable, and 9 of the TRV's are programmable, but I would not think anyone today lives in a home with one thermostat, and few still use a programmer, most today have the programmer and thermostat combined. So rather pointless advice given.

Cost of appliances again pointless, not worth buying new freezer, or washing machine to get a more efficient model, and I question cost of boiling a kettle, my kettles, yes I use two, boil a measured amount of water each time used, yes the larger of the two has setting to leak back water so it uses more power to the one with fixed cup size, but can't see the amount of power is anywhere near that high. I have no second hand on my wrist watch, but it takes less than a minute to make two cups of coffee, 6000 watt / 60 is 100 so at 28p per kWh that's 2.8p for two cups of coffee for heating the water, 6.37p will cover over 4 cups of coffee.

Clearly the better insulated the home the less energy used, but I am just about to fit a new patio door, it is costing more than my fuel oil for two years, may safe energy, but will not save money, the turning down of the temperature in that room saved a lot more, door being changed as double glazing has blown, and it looks bad, and possible could leak, but room only used in the summer, so it will not help my bills.

 

[pcaouolte]

Starting at the top. My 800W microwave uses 1400W. The 800W is the output from the magnetron, presumably more electrical power goes in than microwave energy comes out. Then the motor to turn the turntable uses some power as does the light. My microwave is quite old so it is possible that newer ones are more efficient but I doubt that any of them can give 800W of heating for 800W or electrical energy consumed.

So the whole thing is not very well researched.

 

[DetlefSchmitz]

...on my wrist watch

You need to visit a second hand shop.

 

[ericmark]

I did put off power saving and small kettle takes 45 seconds and large one 60 seconds, think both around the 3 kW mark, however we can all work out if you boil one cup of water it takes less energy than boiling 6, rather pointless repeating that.

@pcaouolte makes a good point, it is the power in we are interested in, not the power out.

I bought a power meter some thing like this, years ago, however I soon got bored with it. In the main power used is written on the appliance, but anything with thermostatic control we do need to see how long it is actually switched on for.

I went to my CU armed with my clamp on to measure what my boiler used, with the idea of making it so I could keep it running in a power cut, and I did note using 2.5 amp before starting the boiler, my PC was running, and some lights were on, the Sky box, and clocks galore in everything from Microwave, cooker, thermostat, router, and alarm clocks, the white box was connected to a current transformer, but batteries leaked, keep intending to make it USB powered, on my to do list.

But to turn off RCBO's one by one I may work out exactly where the 2.5 amp is going, but then spend an hour resetting clocks etc. Even the smoke alarms must use some power not that I would turn them off.

I can reduce my winter power very easy, turn off the FCU supplying the boiler, the things I can't control are the council tax bill. Road fund licence. And little I can do about insurance. But having an idea what some thing costs does help.

So around 2 grams of instant coffee per cup, so 100 cups per jar so 1.5p milk £1.50 for 2 litres of milk, so around another 1.5p and as said 1.4p to boil the water, so 4.4p a cup, or around 12p a pint. Compare that with my home brew, around £14 for 40 pints, so 35p a pint, so coffee around a third of price of beer, so in the pub £3 for pint of beer, that means a cup of coffee should be around 75p to match prices.

So

For example, since 1 October it costs 3p to heat up a frozen ready meal in a 800W (watts) microwave for seven minutes.

is helpful, as @pcaouolte says 1400 watt in for a 800 watt output, so when I do the sums I get 1400x7/60 = 0.16 kWh so x 28p per kWh = 4.6p. However most my ready meals from frozen are twin times, of 6 minutes and 10 minutes with a stir between them, so more like 10.5p times given by BBC seem to be for chilled ready meal.

To be frank, a potato done in a microwave, oven, air fryer, or deep fat fryer taste very different, so seems pointless to compare.

My old house even with a double door at front and well fitting door at rear, high winds and the air when through the house, did not matter how many draft excluder's were used, this house with 4 sets of doors on middle floor and two sets on lower floor, our position in the valley means very little draft. There is a cat flap on lower door, would have never fitted one in the old house, wind would have held it open.

Thing is if when we can see errors the BBC is so far out, what can we believe with other reports, they are reduced to a comic.

 

[JohnW2]

I was looking at the BBC web site with "Use an air fryer or microwave instead of an oven" advice, giving details of cost of cooking a baked potato.
5p in a microwave (800W for 10 minutes)
26p in an air fryer (1000W for 45 minutes)
£1.02 in an oven (2000W for 90 minutes)

There are obviously a good few inaccurate and/or iffy 'facts' and assumptions involved in those numbers.

However, I think the conceptual (qualitative) principle is sound, at least when cooking something as small as one potato. An air fryer will use ('waste') more energy than a microwave in heating things other than the potato, and the same (considerably) more so for an oven.

Kind Regards, John

 

[Why Not Indeed]

So the question is does pre-cooking the pair of potatoes in the microwave for 10 minutes, then transferring them to the oven to complete the cooking, together with the pizza use more or less energy to switching oven on earlier and baking only in the oven?

That's what I do, not specifically to save money, but because it's quicker. Although since I last did spuds a relative told me they cook them in the microwave then crisp them in a frying pan on the top, so I will be trying that approach next time.

To your more general point, the article you linked to is for general consumption, it's not an academic study. So long as the general principles are sound, going too much in to detail is [unfortunately] going to put off the target audience.

 

[Rodders53]

Washer and Dishwasher: read the manuals for your exact model?

They often give the energy/water used on different load, cycle type and temperature settings, especially nowadays. (Though maybe not as many of the options as one might hope for).

Longer eco washes often save energy and water by soaking the clothes or dishes for a long time with intermittent motor only agitation. Shorter cycles often use more motor power to agitate. But all modern machines are now even able to adjust the cycle depending on the dirtiness of the water and may add extra rinses, as required: so even the manuals' figures are based on assumptions.

My Miele washer lists some where the water temp reached during a cycle is significantly lower than the 'set' temperature, which I found illuminating.