A geyser blanket is an additional layer of insulation designed to be wrapped around the geyser. Most products available typically consiss of a 50mm layer of glass fibre insulation with a reflective foil sheeting cover on one side. However the thicker the insulation the better (100-150mm is not much more expensive but it is twice or three times as effective).
Pipe Insulation
Arguably its far more important to insulate all pipes leading to/from the geyser. This is because these pipes are usually not insulated at all, while the geyser is usually very well insulated to begin with, so adding a geyser blanket only yields marginal benefits. All pipes leading in/out of the geyser should have a layer of insulation wrapped around them for at least 2-3 meters. One should ideally insulate the full length of all hot water pipes. There are a number of suppliers and installers that have specialised products that are designed to quickly and efficiently insulate a wide range of pipe sizes and types.
Alternatively one can simply use approved ceiling insulation and duct tape or cable ties!
What Benefit Do You Gain From a Geyser Blanket?
Electrical geysers heat water by means of a large electrical element similar to that found in your kettle. They have a thermostat that switches the heating element off when the water reaches a preset temperature. That thermostat will also switch the heating element back on if the water drops below another lower preset temperature. (See our geyser load profile test for more info).
Once the water is heated, it slowly starts to cool via heat transfer out of the geyser through the geysers’ insulation as well as via cooling of the water in the hot water pipes leading out of the geyser. The slower this cooling happens, the less often the geyser element is switched on to heat the water and hence the less electricity is consumed.
The repeated re-heating of water between times that anybody actually uses any hot water, is wasteful, because energy is consumed simply redoing what was already done before. As far as possible this should be reduced.
A good geyser blanket reduces the rate of cooling of the water inside the geyser considerably. Further more, geyser blankets are relatively inexpensive and easy to install.
Installation
If you buy a geyser blanket kit, it should include instructions on how to install it properly. There are number of suppliers and installers who specialise in geyser blankets.
Alternatively one can make up one’s own blanket by using approved ceiling insulation (preferably 100mm or 150mm thick) with an outer layer of some form of aluminium foil based reflective sheeting (even heavy duty kitchen foil will work). The outer layer of foil is less important than using thicker insulation because most of the heat is lost via convection and conduction, so if necessary the foil can be neglected.
Essentially one needs to simply wrap the insulation around the geyser and secure it in place with some tape such as duct tape. Be careful not to wrap the tape too tightly and squash the insulation flat. If that is unavoidable, you should wrap another layer of insulation over the parts that have been squashed flat. Be sure the top of the geyser is insulated (warm air and water rises so most of the heat will be lost out of the top of the geyser).
