Can I Add Additional Solar Panels to My System?

Expanding your solar panel system can be a smart move for UK homeowners, landlords, and commercial property owners looking to boost energy savings and reduce carbon footprints. 

With rising energy costs and supportive government schemes, the question “Can I add additional solar panels to my system?” is increasingly common. This guide discusses the feasibility, benefits, and considerations of upgrading your solar setup, tailored for UK properties. 

Whether you’re aiming to meet growing energy demands or maximise your return on investment, we’ll provide clear, practical insights to help you decide.

Can You Expand Your Existing Solar Panel System?

Yes, adding more solar panels to your system is often possible, but it depends on several factors, including your current setup, roof space, and electrical infrastructure. 

According to the Energy Saving Trust, over 1.3 million UK homes had solar installations by February 2024, and many are now considering expansion to meet rising energy needs or take advantage of schemes like the Smart Export Guarantee (SEG). 

Below, we break down the key considerations to determine if expanding your system is viable.

Is Your Roof Suitable for Additional Panels?

Your roof’s size, orientation, and condition play a critical role in determining whether you can add more solar panels. South-facing roofs with a pitch of 25° to 45° are ideal for maximising solar energy production in the UK, though east- or west-facing roofs can also work. 

Shading from trees or nearby buildings can reduce efficiency, but technologies like solar optimisers can mitigate this by ensuring shaded panels don’t affect the entire system’s output.

Action Step: Consult an MCS-certified installer to assess your roof’s suitability. Use Eco Answers’ Quote-Comparison Tool to connect with professionals who can evaluate your property.

Is Your Current System Compatible with Additional Panels?

Your existing solar panel system’s components, such as the inverter and wiring, must be compatible with additional panels. 

Most UK systems installed after 2010 use inverters with a capacity of 3–4kW, suitable for an average household consuming 2,700 kWh annually. However, adding panels may exceed your inverter’s capacity, requiring an upgrade.

• Inverter Capacity: The inverter converts DC electricity from panels to AC for home use. If your current inverter is at capacity, you’ll need a larger one or a secondary inverter.
  
  
• System Age: Older systems (pre-2010) may use outdated technology, making integration challenging. Modern panels are more efficient, but compatibility issues can arise.
  
  
• Wiring and Connections: Additional panels may require rewiring to ensure safe and efficient operation.

Example: A 3kW system with 10 panels might support 4–6 additional panels, depending on the inverter. A professional assessment is essential to confirm compatibility.

Do You Need Planning Permission for Extra Panels?

In most cases, adding solar panels to an existing system in the UK falls under Permitted Development rights, meaning planning permission isn’t required.

However, there are exceptions, particularly for listed buildings or properties in conservation areas, where approval from your local planning authority is mandatory. Always check with your local council to confirm.

What Are the Benefits of Adding More Solar Panels?

Expanding your solar system can enhance energy production, reduce bills, and increase property value. Here’s why UK homeowners, landlords, and commercial property owners should consider this upgrade.

Cut Electricity Bills

Adding solar panels can significantly cut electricity bills. According to the Energy Saving Trust, a 4kW system can save up to £630 annually in London for households at home most of the day. 

With Ofgem reporting a 30% rise in electricity prices between 2022 and 2024, generating more solar energy reduces reliance on costly grid power.

• Smart Export Guarantee (SEG): You can earn 10.8p–21p per kWh for surplus energy exported to the grid, with some suppliers like E.ON Next offering up to 21p/kWh.
  
  
• Battery Storage: Pairing extra panels with a solar battery can store excess energy for evening use, increasing savings to around 80% of your solar generation.

Case Study: A homeowner in Leeds with a 3kW system added 6 panels and a battery, reducing their annual bill from £1,200 to £150, a saving of over £1,000. Take a look at our guide on solar battery costs to get a clearer picture of what you can expect to pay.

Increase Property Value

Solar panels can boost property appeal and value. Solar Energy UK reports that homes with solar systems can increase in value by up to 2%. A 2023 government survey found 70% of owner-occupiers are likely to consider installing solar panels, indicating strong market demand.

• Landlords: Solar panels attract eco-conscious tenants and enhance rental property appeal.
  
  
• Commercial Properties: Energy-efficient buildings command higher rents and attract sustainability-focused businesses.

Reduce Carbon Footprints

Each kW of solar capacity reduces CO2 emissions by approximately 0.25 tonnes annually. Expanding a 3kW system to 5kW could cut an additional 0.5 tonnes of CO2 per year, supporting the UK’s net-zero goal by 2050. 

This is particularly appealing for eco-conscious homeowners and businesses.

What Are the Costs of Adding More Solar Panels?

Expanding your solar system involves upfront costs, but incentives can offset these. The Federation of Master Builders estimates a 4kW system costs £5,000–£8,000, with additional panels typically costing £300–£500 each.

What Are the Installation Costs?

Incentives:

• 0% VAT: Until March 2027, solar installations benefit from zero VAT, saving up to £2,850 on a 4kW system.
  
  
• ECO4 Scheme: Low-income households may qualify for free or subsidised installations.
  
  
• Warm Homes: Social Housing Fund: Social housing landlords can access funding for solar upgrades.

Use Eco Answers’ Quote-Comparison Tool to get tailored quotes from MCS-certified installers.

How Long Is the Payback Period?

The payback period for additional panels typically ranges from 8–12 years, influenced by energy prices, SEG earnings, and system efficiency.

Rising energy costs have reduced payback times by 2.5 years since 2022. For example, a £6,000 investment in a 4kW system could break even in 9 years with annual savings of £630 and SEG earnings of £150.

What Are the Technical Considerations for Expansion?

Adding panels requires careful planning to ensure system efficiency and compliance with UK regulations.

Register with the Distribution Network Operator (DNO)

Any expansion of your solar system must be registered with your DNO, typically handled by your installer. Systems exceeding 3.68kW (16 amps per phase) may require prior DNO approval to ensure grid stability.

Consider Battery Storage

Adding a battery can maximise the benefits of extra panels by storing surplus energy for use during peak hours. A typical 5kWh battery costs £4,000–£8,000 but can increase solar consumption from 50% to 80%, saving an additional £200–£300 annually.

Are There Alternatives to Adding Panels?

If adding panels isn’t feasible, consider:

• Upgrading to High-Efficiency Panels: Modern monocrystalline N-type panels, like SunPower Maxeon 7, offer up to 22% efficiency.
  
  
• Optimisers or Micro-Inverters: These improve performance in shaded areas without adding panels.
  
  
• Energy Efficiency Measures: Pair solar with heat pumps or insulation to reduce overall energy use.

FAQs 

Can I add panels from a different manufacturer to my existing system?

Yes, but compatibility is key. Different manufacturers may have varying panel specifications (e.g., voltage, wattage). An MCS-certified installer can ensure the new panels integrate seamlessly with your current system, avoiding efficiency losses.

Will adding panels affect my existing Smart Export Guarantee (SEG) tariff?

Expanding your system may require reapplying for an SEG tariff, as rates depend on system size and supplier. Contact your energy supplier to confirm. Some, like E.ON Next, offer premium rates (up to 21p/kWh) for customers with their installations.

Can tenants request additional solar panels on rental properties?

Tenants can request solar upgrades, but landlord approval is required. Highlight benefits like lower energy bills and increased property value. Schemes like ECO4 may cover costs for eligible low-income tenants.

How do I know if my roof can support the weight of extra panels?

A structural survey by a qualified engineer is essential. Most modern UK roofs can support additional panels, but older or flat roofs may need reinforcement. Your installer can arrange this assessment.

Can I add panels to a system installed before 2010?

It’s possible, but older systems may have outdated inverters or wiring, requiring upgrades. Consult an MCS-certified installer to evaluate compatibility and ensure compliance with current standards.

Conclusion

Adding additional solar panels to your system is a viable option for UK homeowners, landlords, and commercial property owners aiming to enhance energy savings, reduce carbon emissions, and increase property value. 

By assessing roof suitability, system compatibility, and costs, you can make an informed decision. Government incentives like 0% VAT and ECO4 scheme, combined with SEG earnings, make expansion more affordable. 

Use Eco Answers’ Quote-Comparison Tool to connect with trusted installers and start your solar upgrade journey today.