What is the cheapest way to cook food? | UK Financial Crisis

I've been reading a lot of articles recently dedicated to advising what kitchen gadgets are the most cost effective. I've found it interested to learn about how different kitchen appliances and gadgets cost different amounts to run and how they cook food in different lengths of time. 

I found this article interesting, about how Air Fryers are more cost effective than ovens when cooking most food. I've had our air fryer now for i think almost a year and it has been great. I realised though i haven't been making full use out of it, there have been times i've used an oven when i could have used the air fryer. Only very recently did i realise i could cook a frozen garlic bread in the air fryer for a fraction of the time it would have taken in the oven. 
- Read the BBC article here. 
- Take a look at the double air fryer i use here 

I've also read a number of articles about how using a slow cooking is more cost effective than cooking on a hob. This is something i want to so a little more research on and see some more data evidence before i make a final judgement but regardless i do use the slow cooker more often than the hob out of convience. I can chuck everything in the slow cooking before going to work in the morning, switch it on low and when i get home from work and the kids home from school we have a lovely warm meal waiting for us. So in the sense of time saving and effort saving our slow cooker has been fantastic, if it also saves us money in comparison to cooking on the hob that would be brilliant. 
- Take a look here at the slow cooker we have 

My favourite kitchen appliance, or gadget I suppose you would call it is my soup maker. I've not seen enough research to know whether it really does save money in comparison to cooking a soup from scratch on the stove but logically it must. In just 19mins this soup maker turns raw vegetables into a delicious soup. I can opt for smooth or chunky soup, i usually opt for smooth, it does the cooking and blending for me. I can't imagine it would be cheaper to use multiple kitchen gadgets to make the soup and i would think it would take longer on the hob too. It is so easy and quick to use that I've not made a soup on the hob since getting this gadget. It is honestly brilliant. The one i have is only big enough to make soup for 2, though there are other size ones that can make soup for 4 people. 
- Take a look here at the soup maker i have 

It is worth researching the kitchen appliances you have at home and figuring out which ones you have that are the cheapest to cook with, it could really help you save money. If you don't have access to some of the money saving kitchen appliances and gadgets i've mentioned above it might even be worth saving up for them, looking at them as a long term money saving investments or asking for one for a upcoming birthday / Christmas present even? It's certainly worth thinking about.