Heat (specifically heat retention) is a very important factor in every method of brewing coffee. Often, the main reason the coffee you brew at home tastes different than it does at a cafe, is because home brewers simply don’t get the water hot enough.
While coffee should be brewed at temperatures between 91 and 95 degrees Celsius (195 and 205 Fahrenheit), there is a lot more too it than simply aiming for a temperature in this “range”.
To explain the role heat plays in brewing coffee: think of heat as a “currency”. The more “Heat” you have, the more soluble solids you can “purchase” from the ground coffee. But “more” isn’t always better.
This relates to a topic we will address in our FAQ on “Grinding Coffee”, regarding the relationship between grind degree and length of time the coffee and water are in contact for.
There is a further relationship to understand, one between roast degree and brew temperature. The darker the roast, the cooler the water can be (no cooler than 91C / 195F though).
For those looking to brew a better cup at home, take this to mean that unless you are brewing with a French-Press, Aeropress, or pour-over and can boil the water with a kettle, stick to the dark-roasts for home.
In order to properly extract coffee to the ideal 15% extraction rate, you need to factor in the following in determining water temperature:
1. Method of brewing.
2. Degree of roast.
3. Brew or extraction time.
For example, a dark roast brewed in a French-Press (with a 4-minute extraction time), would result in a temperature requirement between 91 and 92 Degrees Celsius (195-198 F).
Whereas a medium to light roast brewed as an Espresso (with a 20-30 second extraction time), would result in a temperature requirement between 94 and 95 Degrees Celsius (202-205 F).
Of course, there are dozens of combinations of the three factors and the above is simply to provide a reference and starting point for your extrapolations and personal testing.
Remember, at the end of the day, if you like the way it tastes, that’s all that matters!