How Solar Panels Work in the UK

Solar photovoltaic (PV) panels convert sunlight into electricity. Even on cloudy days, UK solar panels generate power, making them a viable renewable energy solution across all regions.

Key Components of a Solar PV System

Solar Panels: Convert sunlight to DC electricity (typically 350-450W per panel)
Inverter: Converts DC to 230V AC for home use (97% efficient)
Mounting System: Secures panels to roof with optimal angle
Generation Meter: Records energy produced for SEG payments
Battery Storage (Optional): Stores excess energy for evening use

UK Solar Generation by Region

South England:~2.9 kWh/m²/day (best)

Midlands:~2.7 kWh/m²/day

North England:~2.5 kWh/m²/day

Wales:~2.6 kWh/m²/day

Scotland:~2.3 kWh/m²/day

Northern Ireland:~2.4 kWh/m²/day

Annual averages. Summer generation 3-5× winter generation.

Typical System Sizes

2-3 kW (8-12 panels): Small home, 2,000-2,500 kWh/year usage

4-5 kW (12-16 panels): Average home, 3,000-4,000 kWh/year usage

6-8 kW (18-24 panels): Large home or small business, 5,000-7,000 kWh/year

10+ kW (30+ panels): Commercial or agricultural, 10,000+ kWh/year

MCS Certification & Compliance

MCS (Microgeneration Certification Scheme) is essential for UK solar installations. It ensures quality, provides consumer protection, and is required for SEG payments.

What is MCS?

MCS is a quality assurance scheme for renewable energy installations. Only MCS-certified installers can install systems that qualify for SEG (Smart Export Guarantee) payments.

MCS Requirements:

Installer must be MCS-certified
Products must meet MCS standards
Installation must follow MCS guidelines
System must be commissioned and tested
Certificate issued within 2 weeks of completion

DNO Notification (G98/G99)

Systems up to 3.68 kW (G98): Simple notification to DNO (Distribution Network Operator). Installer typically handles this. No approval required before installation.

Systems 3.68-16 kW (G99): Application to DNO required. 6-12 weeks approval time. Cannot install before approval.

Systems over 16 kW: Full DNO application with network studies. 3-6 months approval. May require grid upgrades.

Planning Permission

Usually Permitted Development: Most domestic rooftop solar installations don't require planning permission.

Exceptions - Planning required if:

Listed building
Building in conservation area
Ground-mounted system in front of house
Panels protrude more than 200mm from roof
Installation on flat roof visible from street

Always check with your local planning authority before installation.

BS 7671 Electrical Compliance

Solar PV installations must comply with BS 7671 Section 712:

DC isolators at array and inverter
AC isolator at consumer unit
Type B RCD required for solar inverters
Proper earthing and bonding
Solar-rated DC cables (EN 50618)
Overvoltage protection
Generation meter installation

SEG Export Tariffs Explained

The Smart Export Guarantee (SEG) requires electricity suppliers to pay for renewable energy exported to the grid. All MCS-certified systems are eligible.

How SEG Works

When your solar panels generate more electricity than you use, the excess is exported to the National Grid. Your energy supplier pays you for this exported energy.

Typical SEG Rates (2024):

Basic tariffs: £0.03-0.05/kWh
Good tariffs: £0.10-0.15/kWh
Best tariffs: £0.15-0.25/kWh (with smart meter)

Important: SEG rates vary by supplier. Shop around for best rates. Some tariffs track wholesale prices and can be higher during peak times.

Maximizing Export Income

Compare tariffs: Different suppliers offer different rates
Smart meters: Enable time-of-use tariffs with better peak rates
Battery storage: Export during peak price times
System sizing: Oversize slightly to maximize export revenue
Monitor generation: Track export to optimize tariff choice

Self-Consumption vs Export

Key principle: Using solar energy yourself saves more than exporting it.

Example (£0.30/kWh import, £0.15/kWh export):

1 kWh self-consumed = £0.30 saved (not paid to supplier)
1 kWh exported = £0.15 earned (paid by supplier)
Self-consumption is 2× more valuable

Strategy: Use appliances during sunny hours (dishwasher, washing machine, EV charging) to maximize self-consumption. Battery storage increases self-consumption from ~30% to ~70%.

Choosing Solar Panels & Equipment

Panel Types

Monocrystalline (Mono) - Recommended:

Efficiency: 19-22% (highest)
Better performance in low light
More expensive but best value long-term
Black appearance, premium look
Typical UK choice: 350-450W panels

Polycrystalline (Poly):

Efficiency: 15-17%
Lower cost per panel
Blue appearance
Less common now, being phased out

Thin Film:

Efficiency: 10-12% (lowest)
Flexible, lightweight
Rarely used for UK domestic installations

Panel Specifications to Check

Power Output: 350-450W typical for residential (higher is better per panel)

Efficiency: 19-22% for modern mono panels (higher efficiency = more power per m²)

Warranty:

Product warranty: 10-12 years minimum
Performance warranty: 25 years (80-90% output guaranteed)

Temperature Coefficient: -0.3% to -0.4%/°C (lower negative is better)

Low-light Performance: Important for UK climate

Inverter Selection

String Inverter (Most Common):

One inverter for entire array
Most cost-effective
Good for unshaded roofs
97% efficiency typical

String Inverter + Optimizers:

Optimizer on each panel
Better for partial shading
Panel-level monitoring
10-15% more expensive

Micro-inverters:

One inverter per panel
Best for complex roof layouts
Most expensive option
25-year warranty typical

Hybrid Inverter:

Built-in battery compatibility
Future-proof for battery addition
Slightly more expensive

Top Brands (UK Market)

Panels: LG, Panasonic, SunPower, REC, Canadian Solar, JA Solar, Longi, Trina

Inverters: SolarEdge, Fronius, SMA, Enphase (micro), GivEnergy (hybrid), Solis

Batteries: Tesla Powerwall, GivEnergy, Enphase, SolarEdge, sonnenBatterie

Always verify MCS certification for panels and inverters to qualify for SEG.

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