Direction & shading
What affects plug-in solar output? The key factors
Two identical plug-in systems can generate very different amounts depending on where and how they're installed. Understanding the factors helps you set realistic expectations and get the most from a system.This guide pulls the main drivers together as a map to the detail guides. To turn them into a number for your home, use the calculator.
Written and edited by Christopher Panteli
Christopher is the founder and editor of MyPlugInSolar. He oversees the site’s research standards, data tools and editorial process. He is not an electrician or solar installer, and specialist technical claims are sourced from official documentation or reviewed by appropriately qualified professionals.
Sunlight: location and weather
The biggest factor is simply how much solar energy reaches your location across the year. The south of the UK receives more than the north, and any site has far more sun in summer than winter — see plug-in solar in winter. You can't change this, but a postcode-level estimate captures it; that's what the calculator uses.
Orientation and tilt
How the panel is aimed decides how much of the available light it captures. South-facing at a moderate tilt is best in the UK; east or west shifts generation to morning or evening; north is the weakest. Mounting it vertically on a railing or wall trades some output for practicality. The full picture is in direction and angle.
Shading, heat and dirt
- Shading: even partial shade from a tree, chimney or railing can cut output sharply — see shading and plug-in solar.
- Temperature: panels lose a little efficiency when very hot, so a baking still day isn't peak.
- Soiling: dirt, pollen and bird mess reduce output until cleaned — see cleaning small panels.
System size and self-consumption
A bigger system generates more, up to any size limit that applies — see the wattage guide. But generation isn't the same as saving: what you save depends on how much output you use as it's produced, which is solar self-consumption. A modest system you use fully can beat a larger one whose output is mostly exported.
Estimate, don't guess
Frequently asked questions
- What affects how much a solar panel generates?
- The main factors are location and weather (how much sun reaches you), orientation and tilt (how much the panel captures), shading, temperature, dirt, the system's size and how much of the output you actually use as it's generated.
- What reduces solar panel output the most?
- Shading and poor orientation are usually the biggest controllable losses. Even partial shade can cut output sharply, and a panel facing the wrong way or at a poor angle captures far less of the available light.
Sources
- 1. PVGIS (Photovoltaic Geographical Information System) — European Commission, Joint Research Centre
Estimate your solar potential
See how much electricity a small system could generate at your postcode, and the indicative bill saving.