Adding Additional Solar Panels - What You Need to Know

If you already have a system in place, you might be asking, is adding additional solar panels later possible? 

The short answer is yes, but expanding your system comes with a few important considerations.

If you are yet to make the move to green energy, use our solar panel calculator to avoid needing to add additional panels in the future.

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Can You Add Extra Solar Panels to an Existing System?

Ultimately yes, but it depends on your system's setup.

Expanding your solar system can be a great way to generate more energy and cut electricity costs. However, adding panels isn’t always as straightforward as it seems. Factors like roof space, inverter capacity, and grid limitations can impact whether an upgrade is possible.

Before making any changes, it's important to assess your roof’s solar suitability and check if your system can handle the expansion.

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Key Considerations Before Adding Additional Solar Panels

Adding additional solar panels to your system isn’t as simple as just installing a few extra panels - it involves technical, structural, and regulatory factors. Here’s what you need to know before you add extra solar panels to your setup.

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Checking Grid Permission (DNO Approval)

Most residential solar systems in the UK are limited to 3.68kW on a single-phase supply. Exceeding this means you'll need approval from your Distribution Network Operator (DNO) to ensure the grid can handle the extra energy.

• Application Process: If your expansion takes your system over the 3.68kW limit, you’ll need to submit a G59 application to the DNO. Your installer can guide you through this process.
• Timeline: Approval can take up to 11 weeks, and in some cases, the DNO may require system modifications or place restrictions on how much power you can export.
• If Your Request is Denied: You might need to install an export limitation device or even upgrade your grid connection, which can be expensive

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Inverter Compatibility

Your existing solar inverter is likely sized for your current system, meaning it may not support additional panels. Options include:

• Upgrading to a larger string inverter (best if adding multiple panels).
• Installing a second inverter to keep the systems separate.
• Using micro-inverters, which allow independent panel operation and avoid efficiency losses if new and old panels have different power outputs.

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Roof Space and Structural Limits

Even if your system can handle more panels, your roof’s solar suitability is key. Consider:

• Structural Support: Roofs must handle the weight of additional panels. Older or weaker roofs may require reinforcement.
• Cost vs. Benefit: Small expansions (1-2 panels) may not be cost-effective due to fixed installation costs like scaffolding.
• Aesthetic Differences: New panels may not match older ones in color or design, affecting the overall look of your system.

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Financial & Regulatory Implications

Before adding additional solar panels to your system, it’s important to understand the financial and regulatory implications that come with the upgrade. Here’s a breakdown of what to expect.

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Impact on Feed-in Tariff (FiT) & Smart Export Guarantee (SEG)

If you’re already receiving payments through the Feed-in Tariff (FiT) or the Smart Export Guarantee (SEG), adding more panels could affect your earnings:

• Feed-in Tariff (FiT): For homeowners on a grandfathered FiT scheme, adding more panels can affect your payments. If your inverter is upgraded, you may no longer be eligible for FiT payments.
• Deemed Export vs. SEG: Under FiT, deemed export payments are calculated based on your system size, with no need to measure how much energy you actually export. However, with the Smart Export Guarantee (SEG), payments are based on the amount of electricity you actually export to the grid, which requires a smart meter for accurate tracking.
• Sticking with FiT: Many homeowners prefer to keep their existing FiT payments rather than switch to SEG, as FiT payments often offer higher export rates. However, it’s essential to weigh this against any changes caused by adding new panels.

Installation Costs & Return on Investment

Adding extra panels involves installation costs, which can vary depending on the complexity of your system and roof. Here’s what to consider:

• Typical Costs: The main costs will include panels, inverter upgrades, and installation fees (which can be higher for additional panels or complex installations). You may also need to factor in costs for scaffolding or roof reinforcements.
• Return on Investment (ROI): Whether adding more panels is worth the cost depends on how much energy your new system will generate. Consider how the additional energy offsets your electricity bills and whether your energy consumption has significantly increased .

Before moving forward, assess the return on investment by comparing your projected savings with the costs of expansion to ensure the investment is worthwhile.

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Is Adding More Solar Panels Worth It?

Deciding whether to add more solar panels to your system depends on several factors. Here’s when it makes sense, and when it might not.

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When It Makes Sense

• Large Energy Needs: If you’ve added significant energy demands (e.g., electric vehicles, heat pumps), expanding your system can help offset rising electricity costs.
• Battery Storage: If you have or plan to install a solar battery, adding extra panels can help store more energy and improve your system’s efficiency.
• Enough Roof Space: If you have the space and structural support for additional panels, expansion becomes a more viable option.

When It Might Not Be Worth It

• High Costs: Expanding your system comes with installation, inverter upgrades, and possibly structural reinforcement costs. If the savings don’t justify the expense, it might not be worth it.
• Limited Grid Capacity: If your grid connection has limitations, getting approval can be a time-consuming and expensive process.
• Small Expansions: If you’re only adding 1-2 panels, the installation costs may outweigh the benefits of such a small increase in energy production.

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How to Get Started with Expanding Your Solar System

If you’re considering adding more solar panels to your system, here’s how to get started:

1. Check your existing system specs
2. Get DNO approval 
3. Consult an installer

Utilise tools like our solar panel calculator to help assess the feasibility of your expansion. These tools can give you a clearer idea of how many additional panels your system can handle, as well as potential savings and costs.