How do I calculate the potential energy savings from a solar pergola?

To calculate your potential energy savings, follow these steps:

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1. Determine your solar panel setup

• Number of panels: Most UK pergolas accommodate 5-10 panels (e.g., 6x 450W Eurener panels = 2,700W total capacity).
• Efficiency: Modern panels (like 22% efficient models) convert more sunlight to electricity, especially important in cloudy UK climates.

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2. Calculate theoretical daily output

• Formula:
  Total system watts × peak sunlight hours × 0.8 (accounting for real-world losses)
  Example: 2,700W × 3.5 UK daylight hours × 0.8 = 7.56kWh/day
• Annual estimate: 7.56kWh × 365 = 2,759kWh/year
  (Current UK average household uses 2,700kWh annually)

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3. Factor in real-world conditions

• Geography: Southern England outperforms Scotland (e.g., 4 vs 2.8 average peak hours).
• Seasonality: Summer production can be 3x higher than winter.
• Shading: Nearby trees/buildings may reduce output by 15-30%.

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4. Convert to monetary savings

• Energy rate: At 28p/kWh (current UK average), 2,759kWh = £772/year saved.
• Smart Export Guarantee (SEG): Earn 4-15p/kWh for excess power fed back to the grid.

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5. Account for costs

• Installation: £230-690 per panel (high-efficiency models) + £500-1,500 pergola reinforcement.
• Payback period:
  Example: £5,000 system saving £772/year = 6.5 years ROI.
  (Actual range: 5-12 years depending on location and energy use)

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Key pros and cons

Pros	Cons
✓ Dual-purpose shade + power generation	✗ High upfront costs
✓ SEG income potential	✗ Planning permissions sometimes needed
✓ Increase property value	✗ Requires structural assessment

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Common mistakes to avoid

• Oversizing: Installing more panels than your pergola can structurally support (standard UK pergolas often need reinforcement for >10 panels).
• DIY errors: Incorrect roof pitch (optimal 30-40° in UK) can lead to a 10-20% efficiency loss.
• Neglecting maintenance: Dust/pollen buildup can reduce output by 5% monthly without cleaning.

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Real-world UK example

A Surrey-based café installed a 10-panel pergola (4kW system) generating 3,200kWh annually. This covers 80% of their energy needs, saving £900/year while providing shaded outdoor seating that increased customer dwell time by 25%.

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Practical advice: Use the Energy Saving Trust's solar calculator (updated for 2024 rates) to personalize these estimates. Consult a MCS-certified installer for structural assessments and SEG-compliant installations.