Select each source of shade that affects your roof, specify its direction and severity, and we’ll estimate the annual generation loss. You can add multiple shade sources to see their combined impact, plus get recommendations on whether you need optimisers or microinverters.
Shading is the single biggest factor that can reduce your solar panel output — and it’s often underestimated. Even partial shading on a small section of your array can have a disproportionate impact on total generation, depending on your inverter setup.
Understanding your shading situation before installation helps you make informed decisions about panel placement, system design, and whether to invest in shade-mitigation technology like optimisers or microinverters.
The most common cause of shading. Can range from light dappled shade to complete blockage. Deciduous trees change seasonally.
Neighbouring properties, extensions, or taller structures nearby. Impact depends on height, distance, and direction.
Obstacles on your own roof cast shadows that move throughout the day. Usually affects 1-3 panels depending on size.
Small obstacles with minimal impact. Often can be relocated during installation if they’d shade panels.
Most residential solar systems use a string inverter — a single device that converts DC power from all your panels into AC power for your home. Panels are connected in series (a “string”), and the entire string’s output is limited by its weakest panel.
This creates a problem: if one panel is shaded and producing only 50% of its capacity, it can drag down the output of every other panel in the string — even those in full sun.
In this example, one shaded panel (40% output) forces the entire 6-panel string down to 40% — even though 5 panels are in full sun. Total output: 40% instead of the expected 90%.
A single shaded panel doesn’t just lose its own output — it can reduce the entire system’s generation. This is why even small amounts of shading need to be taken seriously, and why optimisers or microinverters are so valuable for shaded roofs.
The actual impact depends on the severity of shading, the direction (south-facing obstacles are worst), and when during the day the shading occurs. Here are typical ranges:
| Shade Source | Light Impact | Partial Impact | Heavy Impact |
|---|---|---|---|
| Trees (nearby) | 5-10% | 15-20% | 25-35% |
| Neighbouring building | 8-12% | 18-25% | 30-40% |
| Chimney | 2-4% | 5-8% | 8-12% |
| Dormer window | 3-5% | 6-10% | 10-15% |
| Aerial/satellite dish | 1-2% | 2-4% | 4-6% |
| Roof vent/pipe | 1% | 2-3% | 3-5% |
Shade from the south has the biggest impact because south-facing panels receive the most direct sunlight. Shade from the north has minimal impact since it rarely falls on south-facing roof sections.
The time of day when shading occurs significantly affects its impact on total generation:
| Time Period | Solar Production | Impact Multiplier | Notes |
|---|---|---|---|
| Morning (6am-10am) | ~15% of daily total | Lower impact | Sun is low, less generation anyway |
| Midday (10am-2pm) | ~50% of daily total | Highest impact | Peak production hours — shade here hurts most |
| Afternoon (2pm-6pm) | ~30% of daily total | Moderate impact | Still significant production time |
| All day | 100% | Severe impact | Constant shade is the worst scenario |
Shading impact changes throughout the year because the sun’s path across the sky varies:
Sun is low in the sky, casting long shadows. Trees and buildings that don’t shade in summer may shade significantly in winter. However, winter production is lower anyway.
Sun is high overhead, shadows are short. Most obstacles have minimal impact. This is also when ~60% of annual production occurs, so summer shading matters most.
Deciduous trees (oak, beech, etc.) lose their leaves in winter, which sounds helpful — but remember, winter is when shadows are longest. Even bare branches can cause significant shading when the sun is low.
The good news: in summer when production is highest, leaf cover may provide only dappled shade rather than complete blockage.
If you have shading issues, two technologies can significantly reduce the impact by allowing each panel to operate independently:
DC-DC converters attached to each panel. Still uses a central string inverter, but each panel optimises its own output.
Small inverters attached to each panel. Converts DC to AC right at the panel — no string effect at all.
| Shade Impact | Recommendation | Why |
|---|---|---|
| 0-10% | Standard string inverter | Losses too small to justify extra cost |
| 10-20% | Consider optimisers | Optimisers can recover 40-60% of losses |
| 20-30% | Optimisers recommended | Clear ROI improvement with optimisers |
| 30%+ | Microinverters essential | Maximum independence needed for viability |
Example: A 10 panel solar system with 20% shading losses:
With 25-year panel warranties, that’s 18+ years of improved returns after payback.
Pruning, crown reduction, or selective removal can be more cost-effective than equipment upgrades. One good trim might save thousands in lost generation over 25 years.
A skilled installer can position panels to avoid the worst shading. Sometimes fitting fewer panels in better positions outperforms more panels in shaded spots.
Splitting panels into separate strings (shaded vs unshaded) prevents shaded panels from affecting clean ones. Requires compatible inverter with multiple MPPT inputs.
TV aerials, satellite dishes, and some vents can sometimes be moved during installation to avoid shading panels. Usually a minor additional cost.