Cylinders and pipes
For any type of hot water storage, energy is lost through the walls of the cylinder even if no hot water is being used. This is called ‘standing loss’.
Modern electric cylinders must have a high level of insulation so that the standing loss is relatively low.
Gas hot water cylinders can’t be fully insulated as they have an exposed flue in the middle where the flame heats the water.
Hot water cylinders are now sometimes installed outside the house to save space.
The cold and rain outside mean that the cylinder insulation needs to be particularly good.
Pipes from hot water cylinders are often not insulated at all and lose a lot of energy. You can buy foam tube pipe insulation from plumbers’ merchants very cheaply.
The first metre of pipe from the cylinder is the most important to insulate but installation can be difficult as pipes are sometimes hidden inside walls.