Octopus Energy recently challenged me to investigate the costs of cooking various recipes using different devices to understand the difference in energy costs.
They kindly sent me smart plug device to get accurate readings when testing the oven, the air fryer, microwave and slow cooker. I was intrigued! If you’re curious to measure your consumption yourself, Octopus have collated tips on how to order your own smart plug. What devices use less energy and still produce great tasting food. Are the savings worth it to invest in an Air Fryer or a Slow Cooker?
I started with the humble jacket potato cooking it in the oven, air fryer and microwave, you can see the surprising results here.
Next was a firm family favourite – Bolognese. I compared the cost of making the Bolognese sauce on the hob versus the slow cooker. Plus I used the same Bolognese to make a lasagna as well.
Starting with the Bolognese Sauce to serve 4 (double up for bulk cooking)
I compared the energy usage and cost of using the hob compared to the slow cooker.
Ingredients
1kg of beef mince
1 tin of chopped tomatoes
2 Onions
2 garlic gloves
Rapeseed oil
Tsp Balsamic vinegar
Tsp of Salt and pepper
2 Teaspoon of oregano
1 vegetable stock cube
Method
You do need to start both recipes on the hob to brown the ingredients.
- Chop the onions and the garlic and cook in a frying pan for a few minutes. Feel free to add in other vegetables at this point for extra health, maybe mushrooms, peppers, carrots.
- Add the mincemeat and cook until brown
- Then add in the tinned tomatoes, oregano, stock, balsamic vinegar and salt and stir.
This is now the point where it needs to simmer and gather flavour, simmer for 30 minutes on the hob at a medium temperature or transfer to the slow cooker and cook for 4 hours.
How Much Energy was Used and what was the Cost?
The total energy usage and cost for just the HOB was 0.1 kwh or 3p for the 10 mins of initial browning, plus 0.5 kwh or 17p for the 30 mins of simmering. A total of 20p.
The total energy usage and cost for the SLOW COOKER was the same 0.1kwh or 3p for the 10 mins of initial browning, plus 0.2kwh or 7p for the 4 hours of slow cooking. A total of 10p.
Please note am using my Octopus Energy Variable Rate Tariff of 34p per kwh (Correct as of 12th May 2023)
Lasagna Extra Method
White Sauce
50g butter
50g plain flour
500ml milk
Melt the butter in a pan, then add the flour and cook for minute or two. Add the milk bit by bit, stirring constantly until you have a sauce. This will only take 5 minutes.
Layer up the lasagna in your cooking dish or slow cooker, meat then lasagna sheets then white sauce. Finish with a layer of white sauce on the top, sprinkle with some parmesan cheese if you like.
Cook in the oven for 30 minutes at 200 or cook in the slow cooker for 4 hours.
Here is the cooked slow cooker version, I was sceptical about how the slow cooker lasagna would taste but can confirm it was LOVELY!
How Much Energy was Used and what was the Cost?
The total energy usage and cost for the OVEN was 0.15 kwh or 5p for the 10 mins of initial making of bolognese plus the 5 mins to make the white sauce. Plus 0.5 kwh or 17p for the 30 minutes in the oven A total of 22p.
The total energy usage and cost for the SLOW COOKER was the same 0.15kwh or 5p for the Bolognese and white sauce on the hob. Plus 0.2kwh or 7p for the 4 hours of slow cooking. A total of 12p.
Please note am using my Octopus Energy Variable Rate Tariff of 34p per kwh (Correct as of 12th May 2023)
Summary
For both recipes it uses around half the energy and cost using the slow cooker versus the hob or oven. Half the cost for more cooking time (and amazing taste) is pretty good though and shows how energy efficient the slow cooker is. Savings can add up over the years and slow cookers start at around £22 on Amazon so could be worth the investment if you plan to use it a lot.
Taste wise the slow cooker intensifies the flavours after cooking for so long. From now on I am cooking bolognese and lasagna in the slow cooker!
This is a collaborative post with Octopus Energy. Find more energy-saving tips and support here.
