Unless you know all the local electrical regulations for your area, and are an accomplished electrician, the connection of a demister pads for light shelf mirror to your house wiring should be left to a professional electrical. In some areas this is a requirement, so check before attempting an installation. Failure to do so may both endanger yourself and invalidate any buildings insurance.

If choosing a heating element to retrofit to an existing mirror, ensure that the correct size is chosen. The element does not need to be the same size of the mirror as the demister effect will extend out across the mirror. Usually if the whole mirror is to be demisted, the element can be 2-3 inches smaller than the mirror on each side. Alternatively if only a small part of the mirror needs to be demisted, a much smaller element can be used.

It is possible to have a demister pads for light shelf mirror installed with a separate switch, so that the heating effect can be turned on and off as required. However the more usual way to install them is into the lighting switch, so that the heating is switched on whenever the bathroom lighting is switched on. The power used by the heating element is very small, typically the same as an incandescent light bulb, so the running costs are very low.