Energy Efficient Appliances: Upgrading to A rated white goods

Screwdriva

In our quest to minimize our household consumption, we have replaced our decrepid old CDA SC222 A rated electric oven for a AEG BPE948730M A++ rated unit (35% off I might add). The hope would be to minimize grid drawn consumption over the life of the appliance. That said, we couldn't find an apples to apples comparable metric on actual consumption anywhere. The energy label for the AEG shares consumption "per cycle" which is the lowest we could find for any oven, but can the older CDA oven specifications show that it consumes 2.2 kWh when on, which it does, but no mention of a "cycle". 

The AEG has quadruple glazing and the higher rating implies greater efficiency somehow. But I'm unaware what the real world difference would be, if any?

Raxiel

Since the elements are always 100% efficient at turning electricity into heat, then its down to how efficient the oven is at turning heat into cooked food.

Presumably that mostly comes down to how much heat is lost from the oven chamber over the cooking period (which the quad glazing will help with) although I suppose the fan design could also help improve cooking efficiency by how well it evens out the temperature.

Auto Shutoff when the timer ends presumably helps reduce waste as well.

We got an A+ rated oven a couple of years ago, but it replaced a horrible old gas range, so I don't know how well it compares directly to lower rated electric models. The glass on the door remains cool to the touch even after an hour of cooking at 200 degrees so I guess it works in that regard.

The oven is still the least energy efficient method of cooking we have though, simply because its full of air that insulates the food from the elements. Other methods like the Deep fat fryer and Hob use another medium to conduct the heat (Oil and water) and the Microwave Oven heats the food directly. The microwave (and hob on lower settings) also draw less than the 'standard' 2 - 2.5 kw heating elements in the other two, meaning there's a better chance of them drawing less than PV can produce. The oven & fryer will always want a little bit of import unless it's really sunny for us.

Air fryers are popular. I don't have one myself, they seem to just be smaller convection ovens. I suppose they can make a saving simply by having less air in the way.

zeupater

Hi

Agree, it's effectively how efficiently the oven keeps the heat in ....

... also, on air fryers, you'll find that their power requirements are far lower than even small ovens and therefore more balanced to the likely output of solar PV ... add to this the low mass of the units reduces preheat times, less volume is being heated, the heat source is generally much closer to the food and the airflow contact with the food is relatively higher than in a standard oven arrangement generally results in shorter cooking cycles.

We use our main ovens very rarely, effectively only when the volume is needed. The preferred go to used to be the combination oven/grill/microwave, but now it's the convenience/efficiency of a small air fryer (ours is ~1kW) that tends to even beat that for small meals/snacks most of the time ...

HTH - Z

Screwdriva

zeupater said:

. The preferred go to used to be the combination oven/grill/microwave, but now it's the convenience/efficiency of a small air fryer (ours is ~1kW) that tends to even beat that for small meals/snacks most of the time ... 

Ironically, if I've understood this new label correctly, our existing air fryer consumes more electricity than our new oven! 

Raxiel

zeupater said:

Hi

Agree, it's effectively how efficiently the oven keeps the heat in ....

... also, on air fryers, you'll find that their power requirements are far lower than even small ovens and therefore more balanced to the likely output of solar PV ... add to this the low mass of the units reduces preheat times, less volume is being heated, the heat source is generally much closer to the food and the airflow contact with the food is relatively higher than in a standard oven arrangement generally results in shorter cooking cycles.

We use our main ovens very rarely, effectively only when the volume is needed. The preferred go to used to be the combination oven/grill/microwave, but now it's the convenience/efficiency of a small air fryer (ours is ~1kW) that tends to even beat that for small meals/snacks most of the time ...

HTH - Z

Makes sense. I would get an air fryer, its just figuring out where we'd physically fit it. Things are a bit crowded at our place.

Reminds me though, the other cooking option I'd not mentioned is even better for solar, and that's the slow cooker. Even an overcast day can usually cover 200W. Made a lot of use of that with the saving sessions.

Raxiel

Screwdriva said:

zeupater said:

. The preferred go to used to be the combination oven/grill/microwave, but now it's the convenience/efficiency of a small air fryer (ours is ~1kW) that tends to even beat that for small meals/snacks most of the time ... 

Ironically, if I've understood this new label correctly, our existing air fryer consumes more electricity than our new oven! 

Depends on how much it draws at the plug and how long it takes to heat up.

One of the biggest energy saving changes we've made over the last few months is to completely ignore the 'preheated oven' part of any cooking instructions. Stick the food in the oven when it's switched on, by the time it announces it's reached the set temperature (which seems to take forever) it's usually only 5-10 minutes longer that the food is done.

Screwdriva

Raxiel said:

Depends on how much it draws at the plug and how long it takes to heat up.

The Air fryer we own consumes 1000W but the new oven is .52 kWh per cycle in fan mode which I believe translates to 520W per hour, almost half the air fryer's consumption?

Raxiel

The air fryer may draw 1kW when it's element is on, but I doubt it's on the whole cooking time though.

Unfortunately high current devices like these aren't really suitable for running through energy meters like the Tapo 110, which makes getting hard numbers a bit more difficult. We just had to estimate it from the IHD total, allowing for the fact other stuff was adding to it at the same time.

I can believe a built in oven has better insulation than an air fryer though.

zeupater

Screwdriva said:

Raxiel said:

Depends on how much it draws at the plug and how long it takes to heat up.

The Air fryer we own consumes 1000W but the new oven is .52 kWh per cycle in fan mode which I believe translates to 520W per hour, almost half the air fryer's consumption?

Hi

I looked at the definition of a 'cycle' as used on oven efficiency labels quite a few years back after wondering what it was really saying .... my suggestion is that everyone should spend a little effort looking at how it's tested & calculated and what that actually means when translated to actual cooking/heating of typical products in the real world in any particular capacity oven .... they may come to the same general conclusion as I did ....

As an example, this afternoon we had some hot sausage rolls as a snack with a coffee ... out of fridge,1000W air fryer, 6 minutes at 180C and they were just right and importantly, ready at around the same time as the drink so really convenient, above that, it was sunny today and whereas there were enough electrons spare to run both the air fryer & kettle (also 1000W) there were definitely not enough to cover a full sized oven .... that's 100Wh of technically free electricity in this instance compared to how many cycles where some electrons would be delivered at a cost? - this is quite important because whereas you could possibly compare one oven with another, it's almost irrelevant in comparing the cycle efficiency or running cost of an oven with any other appliance which could perform the same job - really useful these labels then!!

Anyway, chances are that a full sized oven would have taken well over 6 minutes to even reach 180C without the thermostat cutting out, so were likely looking at (pure guess, but based on experience) 10-12 minutes to achieve the same results .... 3500W (as per appliance spec) for (say) 7 minutes followed by (say) 3500W for 1 of the remaining 4 minutes would result in around 467Wh, so over 4.5x the energy of the air fryer in this instance ....

To perform a sanity check ... the oven spec is 3500W using 1.09kWh per cycle, so if the cycle is ~1hr then that would be 7minutes at 3500W followed by 25% of the remaining 53 minutes (20.25mins total), that's 1.18kWh, so pretty much in line with the 1.09kWh per cycle as per the appliance label ....

Of course, this doesn't suggest that the small capacity air fryer is more efficient as an appliance than a large capacity oven, however, it certainly suggests that it's efficient to select the appropriate tool to perform the job .... a HGV car transporter is efficient at delivering multiple post vans and post vans are efficient at delivering multiple parcels, but whereas multiple parcels can be inefficiently delivered by the HGV, the post van would really struggle to deliver multiple other vans in anywhere near an efficient manner, if at all! ... can I get a turkey in the air fryer?, no ... would I try?, no ... as for heating some sausage rolls in a large capacity oven, well the answer would almost certainly depend on what else was available, so with a combination microwave and air fryer in the toolkit, the answer in my case would also be no ....   

HTH - Z    

Alnat1

I'll go with Z's van idea. My oven is a 7 tonne truck, the sausage rolls are a couple of parcels. I could deliver the parcels in the truck but it costs a lot in fuel. I could buy an Escort type van (air fryer) to deliver the parcels, less fuel but it would take a lot of parcel deliveries to get back the cost of the van in savings. I'd most likely use my car (an appliance I already own) not designed for parcels but quite capable of delivering a few occasionally, no outlay, smaller fuel cost.

I don't own an air fryer. Considered it but in the end, from a money saving view, rejected it. I'd fold a couple of strips of baking paper in half and place the sausage rolls in the folded ends. Lower them into the toaster and in 3 minutes I'd have reheated, non soggy sausage rolls. 

It will take a lot of roast dinners to pay back the cost in energy savings on that AEG oven compared to an average one at less than half the price. Looking at it from a green point of view, it might save a little energy but you've probably sent the old oven that was still working to landfill.

Screwdriva

Alnat1 said:

Looking at it from a green point of view, it might save a little energy but you've probably sent the old oven that was still working to landfill.

The old oven no longer functions. 

zeupater said:

To perform a sanity check ... the oven spec is 3500W using 1.09kWh per cycle, so if the cycle is ~1hr then that would be 7minutes at 3500W followed by 25% of the remaining 53 minutes (20.25mins total), that's 1.18kWh, so pretty much in line with the 1.09kWh per cycle as per the appliance label .... 

Unless I've misread the label, the AEG oven consumes 0.52 kWh per cycle in fan mode, which is the only mode we use (1.09 kWh is standard oven only mode)