A solar quotation can look convincing long before it tells you whether the system is right for your property. The figures may promise lower bills and cleaner energy, but the details determine how much electricity you generate, when you can use it and how reliably it performs. This solar proposal review checklist helps homeowners, landlords and commercial decision-makers compare proposals on what matters beyond the headline price.
The strongest proposal is not necessarily the cheapest or the largest. It is the one based on your building, your consumption and the way you expect to use energy in the years ahead. A well-designed system should make practical sense on day one and continue to deliver value as electricity prices and your needs change.
1. Start with the survey, not the panel count
A credible proposal should follow a proper property survey. For a home, that means considering roof orientation, pitch, usable roof area, shading, roof condition, access and the location of the consumer unit. For a commercial site, it may also mean reviewing half-hourly consumption data, roof loading, tenant requirements, working hours and site operations.
Be cautious if a quotation appears to rely only on an aerial image and a postcode. Remote assessments can be useful at an early stage, but they do not reveal every obstruction, cable route or electrical constraint. Ask what has been surveyed, what remains to be confirmed and whether the final design could change.
2. Check that generation estimates are site-specific
The predicted annual output, usually shown in kilowatt-hours, should be tied to your roof and not presented as a generic figure. A south-facing roof may produce more energy over a year than an east-west arrangement, but east-west panels can match morning and late-afternoon demand better. That can improve the proportion of solar electricity used on site.
Ask whether shading has been modelled. Chimneys, dormers, neighbouring buildings and mature trees can all affect production at certain times of day. The proposal should explain the assumptions behind its estimate, including panel orientation, tilt and expected losses. A precise-looking number without clear assumptions is not a reliable forecast.
3. Compare system size against your actual demand
More panels do not automatically mean better value. Your ideal system size depends on annual consumption, daytime use, export arrangements, available roof space and budget. A household that is empty during the day may benefit more from a battery than from simply adding further panels. A business with consistent daytime load may get excellent value from using solar power directly as it is generated.
Review the proposal alongside your recent electricity bills. Commercial customers should look beyond annual usage and consider the pattern of demand throughout the week. High daytime consumption, refrigeration, production equipment or regular EV charging can materially strengthen the case for solar.
4. Understand the equipment, not just the brand names
A proposal should specify the panel model, inverter model, mounting system and any battery equipment. Brand reputation matters, but so do the technical details: panel output, product warranty, performance warranty, inverter capacity and battery usable capacity.
Check whether the inverter is appropriately sized for the array. It is normal for the panel capacity and inverter rating to differ, but the design should have a clear rationale. If a battery is included, confirm its usable capacity rather than only its headline capacity, its power output and whether it can provide backup power during an outage. Not every battery installation offers backup as standard.
5. Review battery storage on its real role
Battery storage can retain surplus solar generation for use in the evening, helping you rely less on grid electricity. It can also be valuable for properties with time-of-use tariffs, where charging at lower-cost periods may reduce overall costs. However, battery value depends on your consumption pattern, tariff and the size of the solar array.
Ask how the proposal expects the battery to operate. Will it prioritise solar charging? Can it charge from the grid? Is backup capability included, and if so, which circuits will remain powered? For a commercial building, full-site backup may require a different design from essential-load backup. Clear answers prevent an expensive assumption from becoming a disappointment later.
6. Look closely at savings and payback assumptions
Savings estimates should distinguish between electricity you use directly, electricity stored for later and electricity exported to the grid. The value of each is different. Self-consumed solar electricity generally avoids buying power at your import rate, while exported energy is paid at the rate offered by your export tariff.
A sensible proposal should state the assumed electricity price, export rate, annual bill inflation and degradation of panel output over time. It should also make clear whether VAT, financing costs, battery replacement or ongoing maintenance have been included. Treat optimistic projections as scenarios rather than guarantees, especially if they assume unusually high future energy prices.
7. Confirm the electrical and installation scope
The panel array is only one part of the project. Read the scope for scaffolding, roof mounting, cable routes, inverter placement, isolators, consumer-unit work, earthing, export limitation and any remedial electrical work. These items can affect both price and programme.
For listed buildings, flats, leased commercial premises or properties in conservation areas, permissions and approvals may need additional attention. Landlords and managing agents should establish who owns the system, who benefits from the generated electricity and who is responsible for access and maintenance. A good installer will raise these questions early rather than leaving them until installation is due to start.
8. Check permissions, grid connection and compliance
Your installer should explain which notifications, applications and certificates apply to the project. In many cases, the local electricity network operator must be notified or asked for approval, particularly for larger systems, battery storage or installations with export capability. The timing can influence the installation schedule.
Make sure the proposal identifies responsibility for design, paperwork, commissioning and handover documents. You should receive the information needed to register export payments where applicable, as well as electrical certification and clear operating guidance. For commercial projects, ask whether the installer will coordinate around site safety procedures and minimise disruption to normal trading or production.
9. Compare warranties with the aftercare behind them
Long product warranties are reassuring, but they are only part of the picture. Panels, inverters, batteries, workmanship and roof penetrations may each have different warranty terms. Read what is covered, how long the cover lasts, what could invalidate it and who will manage a claim.
Monitoring and responsive support matter just as much. A system that underperforms may not be obvious from a bill alone. Ask whether monitoring is included, who receives alerts and whether performance reporting is available. Shard Solar’s managed approach, from survey through commissioning and aftercare, is designed to give customers one direct team for those questions rather than a collection of separate contractors.
10. Put price in context before making the decision
When comparing proposals, make a like-for-like table. Record the array size, predicted generation, battery specification, equipment models, scope of works, permissions, warranty terms and aftercare. A lower quote may omit scaffolding, monitoring, electrical upgrades or the level of design work needed for a safe, durable installation.
Equally, a higher quote should earn its premium through better equipment, a more appropriate design, stronger project management or clearer ongoing support. Ask for a written explanation of any major difference between proposals. A capable installer should be comfortable explaining why a system has been designed in a particular way and where there is room to adjust the budget.
Questions worth asking before you sign
Before accepting a proposal, ask the installer how they calculated generation, what could alter the final price, whether the battery provides outage backup and which parts of the building it will cover. Confirm the expected installation dates, who will be on site, what access is required and what happens if an issue is found with the roof or existing electrical installation.
For businesses, also ask how the installation will be planned around customers, staff, deliveries and critical equipment. For landlords and developers, establish the metering arrangement and the long-term responsibility for the asset. These conversations are not delays to the project. They are how a proposal becomes a dependable energy system.
A carefully reviewed solar proposal gives you more than a price to approve. It gives you confidence that the system will generate clean electricity, support your energy goals and remain straightforward to own long after the installation team has left.
