This guide helps homeowners plan for solar installation scope, energy assumptions and questions to ask before comparing proposals. The aim is to understand the work, prepare useful information and compare written quotations on a like-for-like basis.
What the project usually includes
The exact scope depends on the property and contractor, but a complete quotation should make the main work visible rather than hiding it inside one total.
- Panel array and inverter specification
- Mounting system
- Electrical connection and monitoring
- Design, approvals and commissioning included in the proposal
Costs that are often quoted separately
These items are common reasons an initial figure grows after a site visit or after work begins. Ask how each will be handled before accepting a quote.
- Roof repairs before installation
- Electrical service upgrades
- Battery storage
- Scaffolding, trenching or unusual access
What usually changes the final price?
Project cost is rarely determined by one national average. The biggest movements usually come from measurable quantity, specification, existing condition, access and local labour or regulatory requirements.
- Roof area and orientation
- Shading
- System size
- Electricity consumption
- Tariff or export rules
- Roof condition and electrical capacity
How to prepare before requesting quotes
- Use at least 12 months of electricity usage when available
- Check roof condition and shading
- Compare system size, equipment and modeled production
- Separate solar economics from unrelated roof replacement work
Compare scope, not just totals
Solar value depends on site production, self-consumption, tariff, export rules, system life and financing. A single payback number without assumptions is not enough.
Keep an uncertainty allowance
Until hidden areas are inspected, treat uncertain items as allowances or contingency rather than pretending the first estimate is a guaranteed final price.
Questions to ask the contractor
- Use your own electricity history
- Check whether roof work is needed first
- Compare equipment, warranties and production assumptions
- Treat savings projections as scenarios, not guarantees
USA and UK context
Incentives, export compensation, tax treatment and grid rules differ between the U.S. and UK and can change. Verify current programs with official sources before making a financial decision.
How to compare two quotes fairly
- Check that both quotes cover the same measured area or quantity.
- Compare product or material specification, not only brand names.
- Mark what is excluded: removal, disposal, access, permits, testing and making-good.
- Identify allowances and provisional sums that can change later.
- Compare warranty, schedule and payment terms after the scope matches.
Use estimates as a planning range
Once you have comparable real quotations, use the Repair Budget Planner to apply a contingency to the low and high ends. The result is a budgeting range, not a contractor guarantee.
Frequently asked questions
Should I replace an old roof before solar?
If significant roof work is likely soon, coordinating the projects can avoid later panel removal and reinstallation.
Why do solar quotes with the same kW size differ?
Equipment, roof layout, inverter type, monitoring, warranties, access, battery options and financing can differ.
What data should I compare?
System size, modeled annual production, assumptions, equipment models, warranties, cash price and any financing terms.