This is a short explanation of consumer surplus. I hope this helps make things simpler
In any given product there will be demand no matter what the price. I realise the magnitude of the demand may vary but the point is if, for example we are looking at the demand for exercise machines - whether the price is £400 or £4 there will always be someone ready to buy it (the amount of people who want to buy it will vary with the price).
We can see a similar situation in reality whether it is Primark or Harrods there is still a demand just the amount of it varies.
Now you must be wondering how does consumer surplus fit into this but it does. The market equilibrium for exercise machines may be £100 so the vast majority of supply will sell them for £100. If we imagine that all suppliers sold them for £100 then the consumers who were already ready to pay to pay over £100 will be gaining an advantage. It is almost like a profit they are making.
Subsequently, consumer surplus is defined as the value that consumers gain from consuming a good or service over and above the price paid.
We can see this clearly in a diagram:
The orange bit shows the consumer surplus - the consumers who are benefitting from the current market equilibrium price.
However, this is not all your need to know! You must know how to valuate consumer surplus. This is done through simple maths...calculating area of a triangle.
The formula for the area of a triangle is 0.5 X Base X height...
So in the diagram above the quantity OP1 is equal to the base which in this case is 100. The next bit is to identify the height and this is the difference between the market equilibrium price and the price where the demand is lowest. In this case it is the from £50 to £100 so the height is 50 (100-50).
The we multiply 50 by 100 by 0.5 and we get a consumer surplus of 2500.
That is how simple it is....
However, in exams the may frighten you by shifting the demand curve and saying what is the new consumer surplus. So remember the same principles apply you are looking at the price where there is demand is lowest and the new equilibrium price!
In economics consumers always just feel price changes.
What I have learnt when doing questions is that I miss read the questions so you have to be careful as to whether the question says what is the difference in the consumer surplus and what is the consumer surplus.
I hope this helps :)