An electric egg boiler is a useful tool if you are short of hob space or just want to boil several eggs in one go without them bashing against each other. Another advantage is that you can just leave it to get on with its job and the eggs start cooking straight away, so there's no need to wait for water to boil.
The amount of water used, determines the hardness or softness of the eggs. The egg boiler comes with a small measuring jug, with which you calculate how much water you need, taking into consideration the number of eggs boiled and the degree of firmness you require. It is also necessary to prick the eggs before cooking and an egg pricker is usually provided with the boiler. A buzzer will go off when the eggs are ready.