Questions to Ask Your Installer Before Buying Solar Panels

If you’re thinking of investing in solar energy for your home, choosing the right installer is as important as choosing the right system. When it comes to the system itself, there are so many variations, it can be difficult to compare quotes and be sure what your investment will buy you. Whether you're considering solar panels, battery storage, or a complete solar and battery storage system, asking the right questions can help you compare quotes, avoid costly mistakes, and choose an installer you can trust.

The following questions will help you compare installers and ensure your system is safe, efficient, and built to last. 

Qualifications and Experience

Are you MCS certified? 

The Microgeneration Certification Scheme (MCS) is the industry standard in the UK for solar PV installations. It ensures that your installer meets strict quality and performance standards and is essential if you want to receive Smart Export Guarantee (SEG) payments. To receive Smart Export Guarantee (SEG) payments for surplus electricity exported to the grid, your installation must be carried out under the MCS or an equivalent certification scheme recognised by the energy supplier. Installations carried out by non-certified companies, including most DIY systems, are generally not eligible. You can check whether an installer is MCS certified by searching the MCS website before signing a contract.

• Are you a member of RECC (Renewable Energy Consumer Code)? 
• How long have you been installing solar systems?
• Can you show me recent local installations?

It’s a good idea to check what previous customers have said about the installer and their company. You can do this by checking reviews on the company’s website or by looking for an independent review on Checkatrade. Obtaining at least three quotes will put you in a much stronger position to compare each installer's experience, proposed system design, warranties, and overall value.

System Design

Can you provide a customised solar PV design based on my home and energy usage?

A good installer should do more than recommend a standard package. They should assess your electricity consumption, inspect your roof, discuss how and when you use energy, and understand any future energy goals, such as buying an electric vehicle or installing a heat pump. This information should be used to recommend a system that's the right size for your home and your energy needs.

To design a solar PV system that works for you, your installer should do the following:

Review your electricity consumption:
Your installer will usually do this by asking for your last 12 months of electricity bills or smart meter data. This helps them understand how much electricity you use throughout the year. The total of your yearly kilowatt-hours is used to determine your daily average. Your installer should also discuss when and how you use electricity throughout the day. For example, your installer needs to know whether you work from home, or you are out all day. A household that's occupied during the day can make greater use of electricity generated directly from the panels while a household that's empty during the day may benefit more from adding battery storage to shift surplus energy into the evening. Your installer will note any appliances you have that use a lot of electricity like electric showers, hot tubs, or induction hobs. They will also want to know whether you have an electric vehicle or are planning to install a heat pump in the future. 

Assess your roof:
Your installer should assess your roof to determine how many solar panels it can accommodate. This includes looking at the available roof space, its orientation, pitch and any shading from trees, chimneys, or neighbouring buildings. The aim is to maximise the value of the electricity you generate, rather than simply fitting as many panels as possible. 

How Many Solar Panels Can Your Roof Hold?
To calculate how many solar panels your roof can hold, your installer will measure your total roof area by measuring the length and sloping height of each usable roof section. They will then subtract space for gaps and obstacles like chimneys, skylights, roof windows, and vents, and divide the remaining usable square metres by the size of a single standard solar panel. A standard residential solar panel occupies approximately 1.7 to 2.0 square metres. Your installer will also allow approximately 15% to 20% of your total area for edge clearances, wind load spacing, and airflow.

Orientation and Tilt:
Solar panels work best when they face due south, which maximises electricity generation although southeast- and southwest-facing roofs can still perform well, often producing only slightly less electricity. East- and west-facing roofs can also be worthwhile, particularly where electricity demand is spread across the day.

To catch the most sun, panels need to be tilted at an angle of 30 to 40° from horizontal, about the same as the average pitched roof. If the panels are installed on a flat roof, or even standing on the ground, they can be placed on frames which tilt them at the optimum angle. 

How Shaded is Your Roof?
All solar panels are negatively affected by shading. Even relatively small areas of shading from nearby buildings, trees or chimneys can significantly reduce a system's output, particularly if the panels are connected in a conventional string configuration. It’s important that your installer knows whether the site will be shaded at all throughout the year, and to what extent, before going ahead with an installation. 

If part of a panel is shaded, the shaded cells can’t generate the same amount of electricity as the cells in full sun, and they can restrict the current flowing through the string. This can result in cells being damaged as the blockages may cause overheating. 

Your installer can use Google Maps as a starting point because it can provide a rough indication of whether there will be shading from nearby buildings, trees, or other street features. 
There are a few solutions that your installer could employ to mitigate the effects of shading. If there is not too much shading, they could choose to leave shaded sections empty and place panels only in the sunniest spots. They could opt to split the array across multiple unshaded roof faces (such as east- and west-facing sections) instead of a single blocked area. If appropriate and permitted, trees may be pruned to reduce shading. Alternatively, microinverters can be used. A microinverter can be installed on each panel so that a shadow on one panel does not reduce the power output of the rest of the string. Another method they can use is to add optimisers to panels to optimise the DC power from each panel independently before sending it to a central inverter. And lastly, Modern panels include bypass diodes that help reduce the effects of partial shading by allowing current to bypass shaded sections of a panel without shutting down whole sections or overheating.

To calculate your potential system size, your installer will multiply the number of panels by the individual panel wattage (e.g., 400W) and divide by 1,000 to get the kilowatt-peak (kWp) capacity.

If you want to speed up the process, there are things you can do yourself such as using a digital tool like the Renewable Energy Hub Solar Calculator or satellite tools to view your roof dimensions.

Which brands of solar panels, inverters and batteries do you recommend, and why?

As there’s a huge choice of products on the market it is advisable to ask your installer what makes his equipment choices reliable, efficient, and long-lasting. 

Here are a few suggestions based on proven performance, warranties, and software usability:

Solar Panels

• JA Solar / Jinko Solar: Reliable Tier 1 N-type panels with high efficiency and 25-year warranties. 
• AIKO Solar / REC Group: Premium, ultra-efficient panels ideal for homes with limited roof space. 

Inverters

• Sunsynk (ECCO Hybrid): Smart tariff optimisation, advanced controls, and excellent off-grid capability. 
• Fronius (Primo/GEN24): Premium Austrian-built inverters with outstanding reliability and flexible warranties. 
• Enphase (IQ8): Industry-leading microinverters with panel-level optimisation and a 25-year warranty. 

Batteries

• SIG Energy Storage: Flexible home battery system offering scalable storage, smart energy management and reliable performance.
• Tesla Powerwall 3: High-efficiency battery with integrated inverter and seamless energy management. 
• Fox ESS (H1/EP): Affordable, expandable battery system offering excellent value for money.

How Will the Installation Affect My Roof or Property?

Ask your installer whether the solar panels will be fitted on top of your existing roof tiles or built into the roof itself. Also ask if your roof needs any strengthening before installation. A reputable installer should inspect your roof first and explain which mounting option is most suitable for your home, considering its appearance and any relevant building or fire safety requirements.

Costs and Grid Connection

Ask your installer whether extra costs such as scaffolding, electrical work, DNO (Distribution Network Operator) application and VAT are included in the total quotation. Check whether the installer is handling the DNO grid connection application from start to finish. Before you go ahead with the installation you should ask your installer for an estimated financial payback period and return on investment.

Any good installer should provide you with a financial breakdown which includes the following:

• Estimated annual savings on energy bills
• Payback period
• Export income (if applicable)
• Potential increases in property value
• Ask about time-of-use tariffs and how a battery system can increase ROI by storing excess solar for evening use.

What Warranties and Aftercare Do You Offer on the Equipment and Installation?

Ask your installer what their product and workmanship warranties cover and how long they last. You should look for panel performance warranties of typically 25 years, inverter warranties usually of 5- 10 years with extensions available, battery warranties of 10 years or a set number of charge cycles and workmanship guarantees of between 2 and 10 years depending on the installer. You should also ask your installer if they provide system monitoring apps and ongoing maintenance packages and whether their team or a subcontractor handles repairs if a component fails. 

Conclusion

Investing in solar panels is a long-term decision, so it's important to choose an installer who takes the time to understand your home, your energy usage, and your future plans. A reputable installer should be transparent about the products they recommend, explain the reasons behind their design choices, and provide a clear breakdown of costs, savings, and warranties.

Don't be afraid to ask questions or compare several quotations before making a decision. The right installer will welcome your questions and be happy to explain every aspect of the installation. By doing your research and choosing an MCS-certified installer with a proven track record, you'll be far more likely to enjoy a safe, reliable, and efficient solar energy system that delivers savings for many years to come.

For more information, please see our full guide to getting solar PV quotes here: https://www.renewableenergyhub.co.uk/main/solar-panels/solar-panel-quotes