This is a write up of a project I completed a few years ago. The aim is to move (load shift) the electricity used by my fridge to times when the electricity is cheaper. Where I live (Sydney, Australia) we have very expensive electricity costs, indeed one of the the highest in the world. At it's worst peak electricity is about 54c/KWh. My house is fitted with a time of use (ToU) meter and peak electricity is from 2pm to 8pm every weekday. Off Peak is Midnight to 6am and there is a middle rate (or shoulder as it's called) which is all other times. So, it makes sense to try move ones use of electricity to times where the price is lowest.
The way to achieve that with my fridge was to change the temperature setting on the fridge on a daily basis. Now this is boring and bothersome to do manual but something quite easy for an Arduino. Now, to be honest I don't expect anyone to copy this Instructable to the letter - its based on a specific model of Fridge (Samsung) but I thought I'd share this as its a good use of an Arduino and its a concept I'd like to introduce to all who read this as I believe load shifting is going to be a built in feature of many household appliances like fridges, air conditioners and washing machines in the future. Also, the charging of electrical vehicles will require to be controlled but for different reasons, ie we can't all get home at 6pm and expect the grid to charge our vehicles at the same time!
This project is on a mains (240v AC) domestic appliance. Please do not attempt to do this project if you are not aware of the risks and are competent to carry out the modifications necessary to complete this project. Hopefully this warning dos not discourage you too much as you can do projects like this but it's best to be aware of the risks rather than a victim of them!