Have you ever wondered the amount of heat that goes down the drain when you take a shower??
You could save a lot of money if you kept this energy at home instead of generating the same amount of heat electrically.
I will give you a quick explanation that will be translated into money language at the end:
Water heat capacity is 4181.3J/(g·Kg)
This means if a gram of water gets a degree(not Fahrenheit) colder it will release 4181.3 joules
Lets take the following example:
You will take a shower and spend 80 liters of water.Suppose the water enters the drain at 33ºC and goes to a container where it colds down to 20ºC(supposing the room temperature is 20ºC)
That process of letting the water cool down to 20ºC will realease:
Energy released=Mass of water in Kg * Temperature variation * Water heat capacity
In this example we'll have
Energy released= 80 * 13 * 4181.3
Energy released= 4.348552 million joules
1kWh, wich is the unit of energy the electric company charges us is equal to 3.6 million joules
So we can harvest 1.20793 kWh
In the letter the electric company sends you it is stated the price of kWh
In my case I'd save 18 Euro cents