There are lots of different hot water cylinders available. They vary in capacity and how long they take to heat water up.
Whichever cylinder you choose, you need to make sure it has sufficient insulation. This will improve its efficiency and keep your heating bills low. Nowadays, the majority of cylinders have sufficient insulation, but if you have an older model you might be able to purchase an insulation jacket for it.
It’s a good idea to speak to a professional to get advice on the best hot water cylinder for you and your home.