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Demand for solar energy is soaring across the UK, with a record-breaking 57,000 households installing solar panels in the first quarter of 2025 – over 21,000 of those in March alone. Following the UK’s sunniest spring on record, solar power generation surged by 42%. Combined with falling panel costs and rising energy bills, it’s clear that a solar boom is well underway.
Energy Security Secretary Ed Miliband has announced that most new-build homes will soon include solar panels as standard. Attention is now turning to how solar installations can be scaled up across existing homes.
From June 2025 onwards, an estimated 133,000 additional UK households are expected to install solar panels in 2025. But with rapid growth comes risk – and homeowners could face costly pitfalls if they’re not careful.
George Penny, Solar Expert and Director at The Solar Co, warns of eight common mistakes that could cost homeowners up to £20,000, sharing advice on how these common mistakes can be avoided.
8 costly solar panel installation mistakes that could cost Brits up to £20,000 in fees and lost income
“One of the most common and costly oversights when installing solar panels is failing to properly assess the condition and structure of the roof. An estimated 1 in 5 UK homes currently require roof repairs, and with UK search interest for ‘Solar Panels’ increasing by 57% from January to June 2025, ignoring the current roof conditions of a home before installing panels could prove a costly mistake.
Solar panels are expected to last at least 25 to 30 years, so if the roof requires repairs or replacement within that time, the panels will need to be taken down and reinstalled, costing a further £500 to £2,000 depending on the system’s size and complexity. Therefore, it is essential to assess roof conditions first and foremost, ensuring any repairs are attended to before panels are installed.”
“So-called ‘cowboy builders’ cost the UK economy £10 billion each year – and solar panel installations are not immune. Unqualified or poorly trained installers can leave homeowners facing serious issues, from faulty wiring to roof damage, often leading to expensive repairs and reduced system efficiency.
Choosing an installer who is not certified by the Microgeneration Certification Scheme (MCS) can lead to poor quality installations, invalidated warranties. MCS certification is the recognised industry standard for solar PV in the UK, and using an MCS-accredited installer also provides access to consumer protection via the Renewable Energy Consumer Code (RECC).
Correcting substandard installations can cost up to £5,000, depending on the extent of the issues. Additionally, without MCS certification, you cannot register for Solar Export Guarantee payments, potentially losing £50 to £200 per year in this income stream. Always confirm your installer is MCS-certified and listed on the official MCS database before signing a contract.”
“‘Solar Panel Kits’ have seen a spike in UK search interest increasing by 65% from January to June in 2025. With average labour costs for solar panel installations likely to set homeowners back approximately £300 per day, it can be tempting to consider installing solar panels yourself.
However, improper installation could lead to electrical faults, roof damage and even fires – meaning the cost of DIY installation could quickly outweigh the initial labour costs of hiring a professional. Typical re-pair costs for electrical re-wiring may set you back £500 to £2,000, whilst it’s also worth noting that DIY installations may void warranties on purchases for panels, inverters or any mounting hardware.
By installing solar panels yourself, you may also risk invalidating your home insurance conditions, meaning your insurance provider may not pay-out if an issue arises. Before any decision is made, it’s always prudent to inform your insurer before going ahead with the installation.”
“Between July 2022 and February 2025 obligated energy suppliers have delivered 38,005 solar installations in England as part of the UK government’s ECO4 grant – a government scheme that aims to assist low-income and fuel-poor households.
Although government solar incentives are not available to all citizens, households in England with an EPC rating of E-G and in receipt of means-tested benefits, may be eligible for free solar panel installations where electricity is used to heat their homes. With 3.5 million households in the UK on means tested benefits and 2021 census data showing one in ten households rely on electricity to heat their homes, up to 350,000 households may be missing out on government funded solar panel installations that may typically cost £7,000.”
“Installing a solar panel system that is either too large or too small for your household’s energy use can lead to unnecessary costs or missed savings. An oversized system may generate more electricity than you can use or profitably export, whilst an undersized system may leave you more reliant on grid electricity than necessary. Oversizing could result in an overspend of £1,000 to £3,000, whilst undersizing might cost you £100 to £300 per year in lost savings, assuming standard household consumption patterns.”
“In the UK, most residential solar panel installations are classed as “permitted development” and do not require planning permission. However, exceptions apply – particularly for the more than 500,000 listed properties in the UK, in addition to those in conservation areas, Areas of Outstanding Natural Beauty (AONBs), or those that are listed or near scheduled monuments.
In these cases, planning permission is often required, especially for flat roof installations. Installing panels without the necessary approval can result in enforcement action and potentially unlimited fines. If you’re unsure about your eligibility, it’s best to consult your Local Planning Authority before proceeding.”
“In the UK, any domestic solar installation larger than 3.68 kWp per phase requires prior approval from the local Distribution Network Operator (DNO). Failing to secure this approval can lead to delays in commissioning, forced system redesigns, or limits on how much energy you can export to the grid.
These issues can incur additional costs of £300 to £1,000, depending on the work required to bring the system into compliance. Moreover, delays in DNO approval can prevent you from earning Smart Export Guarantee income until the issue is resolved. A competent installer should manage this process on your behalf, but it is important to confirm that the necessary applications are in place.”
“Whilst cleaning a solar panel may cost as little as £9.50 per panel and an annual maintenance service costing £150, neglecting to maintain solar panels could result in a drop of up to 10% in energy output. This can happen when dirt and debris prevents panels working at full capacity, whilst technical faults may also go unnoticed by homeowners without an inspection carried out by a specialist.
With average households saving up to £3,000 per year on their energy bills, a 10% drop in energy generation due to poor maintenance could cost households £300 annually.”
Solar Panel Mistakes: Breakdown of Max Potential Costs for UK Households in 2025
| Solar Panel Installation Mistakes | Max Potential Cost | Notes |
| 1. Skipping roof inspection | £2,000 | Reinstalling panels after roof repairs |
| 2. Unqualified installer (repairs) | £5,000 | Major fix of poor installation |
| 2a. Lost Solar Export Guarantee (SEG) income | £200/year | Missed earnings without access to Smart Export Guarantee |
| 3. Wrong panel size | £3,000 | Oversizing system unnecessarily |
| 4. DIY installation | £2,000 | Electrical/structural damage & warranty voiding |
| 5. Missed government grant | £7,000 | Full cost of system not offset by ECO4 |
| 6. Planning permission fines | Unlimited | Potential for unlimited fines for listed properties |
| 7. Grid/DNO issues | £1,000 | Rework + delays in SEG income |
| 8. Neglecting maintenance | £300/year | Efficiency loss and potential system degradation if panels are not cleaned and checked regularly |
Notes to Editors
Estimates for domestic solar PV installations for the remainder of 2025 was calculated by extrapolating 2025 Q1 data (57,000) from June onwards.
Search data on Solar Panel keywords was taken from Google Trends on June 6th 2025
About George Penny
Based in Bromley, George Penny is the Director of The Solar Co. He has a passion for leading the UK’s transition to efficient and reliable renewable solutions for households and businesses alike.
About The Solar Co
The Solar Co is a leading UK-based renewable energy installer specialising in solar panels, battery storage, and EV charging solutions for residential, commercial, and new-build properties. Serving London and the South East, including areas like Bromley, Kent, and Croydon, the company is committed to helping customers reduce energy bills and carbon footprints through high-quality, MCS-certified installations.
With a focus on customer education and support, The Solar Co offers an interactive savings calculator, transparent consultations, and assistance with grant applications.
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