• On houses/flats: Usually not, unless panels stick out more than 20cm, go above the roof ridge, or are on a listed building/flat roof.
• On the ground: Permission is needed if panels are over 4m tall, larger than 9m², too close to boundaries, or in sensitive locations (e.g. conservation areas).

Before carrying out any works, you should ensure that permitted development rights apply to your property and have not been removed or restricted by a planning condition, Article 4 Direction, or other designation.

For full details, see the Planning Portal.