Things You Need to Consider Before Installing Solar PV

Solar panel installation is a significant decision that affects your home, your finances, and your energy independence for the next 25-30 years. Before you contact an installer or sign any contracts, you should understand the key factors that determine whether solar panels are right for your specific property and circumstances.

Some homes are ideal candidates for solar, whilst others face challenges that affect system performance or cost-effectiveness. Understanding these factors upfront will help you make an informed decision and avoid costly mistakes.

This guide covers the essential considerations every UK homeowner should evaluate before moving forward with a solar installation.

Key Takeaways

• Your roof orientation and pitch are fundamental; south-facing roofs at 30-40 degrees are optimal
• Roof condition and remaining lifespan matter; replacing a roof after solar installation is expensive
• Shading from trees, buildings, or chimneys significantly reduces output; assess this carefully
• Planning permission is rarely required but listed buildings and conservation areas have restrictions
• Building Regulations Part P compliance and MCS certification are essential for warranty and safety
• Ownership model (outright purchase, financing, or lease) dramatically affects long-term financial returns
• Your electricity usage patterns and property type affect system sizing and ROI
• Grid connection capacity may need upgrades for larger systems (G99 application)
• Future modifications like battery storage should be considered when sizing your system
• Professional surveys and quotes from multiple MCS-certified installers are essential

1. Assess Your Roof Orientation and Pitch

The most fundamental consideration is your roof’s orientation and angle. Ideally, your roof should face south and be pitched at 30-40 degrees for maximum solar generation in the UK.

If your roof faces south-west or south-east, you’ll lose approximately 10-15% of potential output, but the system remains worthwhile. North-facing roofs generate only 30-40% of south-facing output and are generally uneconomical.

Flat roofs are not ideal because panels won’t have the optimal angle, but they can be fitted with tilt frames to achieve the proper angle. This adds cost and complexity but is sometimes the only option for flat-roof properties.

A professional installer will assess your roof orientation and provide accurate output projections for your specific angle. Don’t rely on estimates for different orientations; get a detailed quote for your actual roof.

2. Evaluate Your Roof Condition and Lifespan

Solar panels last 25-30 years. Your roof should reasonably be expected to remain sound for the same period. If your roof is nearing the end of its life (typically 15-20 years for asphalt shingles, 40-60 years for slate or tiles), seriously consider replacing it before installing solar.

Removing and reinstalling solar panels to access your roof for repairs is expensive, potentially costing £2,000-3,000. It’s far more cost-effective to replace your roof first, then install solar on a new roof with another 30+ years of life.

Have a surveyor inspect your roof’s condition. They can advise whether replacement is likely within the solar panel’s lifetime. If replacement is necessary, factor this into your decision-making.

3. Identify and Assess Shading Issues

Shading from trees, buildings, chimneys, or other structures significantly reduces solar output. Even partial shading of one panel in a string inverter system can reduce the entire string’s output.

Walk around your property at different times of day and different seasons. Note which areas of your roof receive shade, and for how long. Trees that leaf out in summer might cast significant shade, whilst winter sun angles mean shade from nearby buildings changes seasonally.

If your roof will be shaded during peak generation hours (10am-3pm), your system will be compromised. In this case, a microinverter system (one inverter per panel) can partially mitigate shading impacts, though at higher upfront cost. Alternatively, you might consider not installing solar if shading is severe.

Professional solar installers often use solar pathfinding software that accurately models shading throughout the year. Use this when evaluating system feasibility.

4. Understand Planning Permission Requirements

Most residential solar installations in the UK do not require planning permission. They’re permitted development under current regulations if:

• The panels don’t project beyond the plane of the roof slope
• For angled panels (on flat roofs), they don’t exceed 0.75 metres in height or breach certain volume limits
• The property isn’t a listed building
• The property isn’t in a conservation area (though solar is often allowed with conservation-style panels)
• The property isn’t in a designated AONB (Area of Outstanding Natural Beauty) or National Park where restrictions apply

However, if your property is listed or in a conservation area, you typically need planning permission or permission in principle. Contact your local authority’s planning department to confirm your property’s status and whether permission is needed.

Your installer should advise on planning requirements, but ultimately it’s your responsibility to confirm. Proceeding without required permission could result in enforcement action requiring you to remove the system.

5. Ensure Building Regulations Compliance (Part P)

All residential solar installations must comply with Building Regulations Part P (Electrical Safety). This is not optional; it’s a legal requirement.

MCS-certified installers automatically ensure Part P compliance. They’ll provide Building Regulations certification proving the installation meets safety standards. This certification is essential for:

• Warranty validity
• Insurance claims (some insurers won’t pay claims on non-compliant installations)
• Future property sales (buyers and their lenders may require certification)
• Grid connection and SEG eligibility (though SEG is technically available without Part P, suppliers often require it)

Never use a non-MCS installer to save money on solar. The risks to warranty, safety, and future property value far outweigh any upfront savings.

6. Choose Between Ownership and Financing Models

How you pay for solar panels dramatically affects your long-term financial returns. There are four main options:

Outright Purchase

Pay the full cost upfront (typically £6,500-8,500 for a 4kW system). You own the panels outright and capture all benefits. Best long-term value but requires substantial upfront capital.

Personal Loan

Borrow at competitive interest rates (typically 5-8%) over 5-10 years. You own the panels and all benefits. Monthly payments are higher than with longer-term financing, but you own the panels quickly.

Installer Financing

Many installers offer financing schemes (sometimes 0% interest for early payoff periods, then interest thereafter). You own the panels and benefits. Terms vary, so compare carefully with personal loans.

Rent-a-Roof / Solar Lease

A third party installs panels at no cost but retains ownership and captures Smart Export Guarantee payments. You benefit from reduced electricity costs but lose significant long-term value. Only consider if you genuinely cannot access other financing options.

Outright purchase or financing with ownership almost always delivers superior financial returns compared to leasing.

7. Evaluate Your Electricity Usage and Tariffs

System sizing should match your electricity usage. A household using 3,000 kWh annually needs a different system size than one using 5,000 kWh annually.

Review your electricity bills for the past year and note your average monthly usage. This helps your installer correctly size your system.

Also consider your usage patterns. Households with people home during the day (retired couples, home-working families) will use more solar electricity directly and benefit more from solar. Households where everyone works outside the home will generate excess electricity during the day and export more to the grid.

Current tariffs matter too. If you’re on an expensive tariff paying 28p+/kWh, solar savings are more attractive. On cheaper fixed-rate tariffs, payback is slightly longer but still typically achievable in 7-9 years.

Consider time-of-use tariffs that reward off-peak electricity use. These can work well with solar as you shift usage to peak generation hours (10am-3pm) and use cheaper off-peak electricity for evening use.

8. Investigate Grid Connection and G99 Requirements

Most residential solar systems (up to 3.68 kWp) don’t require formal grid connection approval. However, larger systems may need to submit a G99 application to your distribution network operator.

If you’re planning a system larger than 3.68 kWp, confirm whether G99 approval is needed. Your installer should handle this, but it can add 4-8 weeks to the installation timeline and potentially involve minor grid reinforcement costs (usually £0-1,000).

If you’re considering battery storage in future, discuss this with your installer as it may affect grid connection requirements.

9. Plan for Future Modifications and Battery Storage

Design your solar system with future flexibility in mind. If you think you might add battery storage in 5-10 years, ensure your system is designed to accommodate batteries.

Battery storage systems work best with three-phase inverters or specific hybrid inverter models. Your choice of main inverter now affects what storage options are available later. Discuss future plans with your installer so they can recommend equipment that supports your long-term vision.

Similarly, if you’re considering a heat pump installation in future, you might want to install a larger solar system now to power the heat pump, rather than adding solar capacity later.

10. Get Multiple Quotes From MCS-Certified Installers

Don’t make a decision based on a single quote. Get detailed written quotes from at least three different MCS-certified installers. Compare:

• System size (in kWp)
• Annual energy generation projection (kWh/year)
• Equipment specification (panel wattage, inverter model, mounting system)
• Total installed cost
• Warranty period and terms
• Installation timeline
• Post-installation monitoring and support

Quotes should be detailed and itemised. Any installer unwilling to provide a detailed written quote should be avoided.

Check installer reviews on Trustpilot, Feefo, and Google. Look for patterns in feedback; isolated complaints are normal, but consistent patterns (poor aftercare, slow timelines, quality issues) indicate genuine concerns.

Case Study: Homeowner Avoids Costly Roof Replacement After Careful Pre-Installation Assessment

Background

A property owner in the Midlands was considering a 5kW solar installation. The property had an ideal south-facing roof and minimal shading. Before proceeding, they commissioned a surveyor’s report specifically checking roof condition for solar readiness.

Project Overview

The surveyor identified that the property’s asphalt shingle roof, installed in 2000, was nearing end-of-life. The shingles were showing deterioration and moss growth, typical of a 24-year-old roof. The surveyor recommended replacement within 3-5 years.

Implementation

Rather than install solar on a roof due for replacement, the homeowner replaced the roof first at a cost of £5,500. Six months later, once the new roof was secure, they installed the 5kW solar system at a cost of £7,800. Total investment: £13,300.

Results

Had they installed solar first, then replaced the roof 3-4 years later, they would have faced the cost of removing, storing, and reinstalling the solar panels (£2,500-3,500). By assessing roof condition first, they avoided this additional expense. Furthermore, their new roof now has 40+ years of lifespan remaining, matching the solar system’s design life. They gained peace of mind and protected their long-term investment in the solar installation.

Expert Insights From Our Solar Panel Installers About Pre-Installation Planning

One of our senior solar panel installers with over 16 years of experience emphasises the importance of getting the basics right. “The most common regret I hear from homeowners is not addressing roof issues before solar installation. A roof replacement after solar installation is expensive and disruptive. Spend £200-300 on a pre-installation roof survey. It’s the best insurance you can buy.”

Another installer notes that understanding your specific circumstances matters more than generic advice. “I regularly see customers who installed oversized or undersized systems because they didn’t fully evaluate their usage patterns and expectations. A homeowner expecting to eliminate their electricity bill entirely might be disappointed if they export 40% of generation at lower SEG rates. Conversely, someone who shifts their daily routine to use more daytime electricity can dramatically improve their ROI. Get a detailed analysis, not generic solar myths.”

Frequently Asked Questions

Summing Up

Installing solar panels is a major decision that requires careful evaluation of your specific circumstances. Whilst solar can be transformative for the right property, rushing into installation without considering these ten key factors can lead to disappointing results or unexpected complications.

Take time to assess your roof, understand your usage patterns, clarify the financing model, and get multiple professional quotes. Spend a few hundred pounds on surveys and detailed assessments; it’s excellent value compared to the £6,500-8,500 installation cost and ensures your investment performs as expected.

If you’re ready to move forward with confidence, our MCS-certified installers can conduct a thorough assessment and provide detailed guidance tailored to your specific property and needs. Contact us for a free survey and quote today.

Updated May 2026