A mirror demister is a heating element positioned behind a mirror to warm a defined area and reduce condensation on the front surface. It is useful after a hot shower, but it is not a magical coating across every part of a large mirror.
The heated area has a boundary
Demisters come in different sizes and shapes. A small pad may clear the centre of a mirror while the corners remain misted. The result depends on the pad, mirror size, room conditions and where the element is positioned.
The heated area should be selected from how the mirror will actually be used.
Control and wiring are part of the design
The demister may be linked to the mirror switch, a separate control or an integrated sensor depending on the product. Electrical planning must be completed by an appropriately qualified electrician, with the bathroom environment and product requirements considered.
The cable route and access should be resolved before the mirror is permanently mounted.
A demister is not ventilation
Heating the mirror can clear its face, but it does not remove humid air from the room. Poor ventilation can still affect paint, ceilings, cabinetry, mirror edges and other materials.
The mirror and extractor solve different problems.
Specify the demister with the mirror
Confirm the demister size, clear area, power requirements, control, service access and compatibility with the mirror before ordering. A premium result is one where the feature works quietly and the electronics remain maintainable.
Read why an anti-fog mirror does not replace ventilation, or see bathroom electrical planning for LED mirrors.