Trees, hedges and your solar panels

Three examples

Our calculation with the shade checker, treating the tree as solid all year. A deciduous tree in winter lets more light through.

Distance matters most: the same tree twice as far away covers a much smaller slice of sky and only reaches the panels when the sun is lower. Height matters next. A hedge only a metre above the panels barely registers unless it is very close.

Your own trees

Before the panels go on, decide what you will do about trees to the south: crown-lift, reduce or leave them. A tree that will grow into the sun's path over the panels' lifetime is cheaper to manage now than to work round later. In a conservation area, or where a tree is protected by a tree preservation order, you may need the council's consent for work.

A neighbour's trees

Government guidance says you can trim branches or roots that cross onto your property from a neighbour's, but only up to the boundary; going further could leave you facing a claim for damaging their property. The same guidance warns that in a conservation area, or where a tree preservation order applies, you might need the council's permission even to trim. Talking to the neighbour first usually goes further than any rule.

High hedges

If a hedge of two or more mostly evergreen or semi-evergreen trees or shrubs is over 2 m tall and affects your enjoyment of your home or garden because of its height, you can ask the council for a complaint form, but only after trying to settle it informally. The council may charge a fee to consider the complaint.

Leaves on, leaves off

A deciduous tree is in full leaf from late spring to early autumn, the months that bring most of the year's output, and bare in winter, when bare branches still throw a lattice of shadow but there is little output to lose anyway. So a broad tree to the south or south-west costs most when it matters most. An evergreen shades all year, but its winter shade costs little for the same reason.

Growth over the years

Panels last for decades, and trees keep growing. A young tree that clears the roof today may not in ten years. When you run the shade checker, try the obstacle at its likely future height as well as its present one, and decide now whether the tree will be managed, within whatever permission it needs.

What the installer should allow for

A tree belongs on the installer's shade assessment like any other obstacle; under MCS's guidance method, one within 10 m of the array is drawn with an enlarged outline to allow for its moving shadow. If the tree will grow, ask the installer to say what the output would be in a few years' time, not only today.

Related pages

• Shade checker
• Measuring an obstacle
• Conservation areas
• Looking after panels

References

1. GOV.UK: high hedges, complaining to the council
2. NOAA Global Monitoring Laboratory: general solar position calculations
3. MCS MGD 005: solar PV shade evaluation procedure (shade factor)
4. St Helens Borough Council: conservation areas