How to compare solar installation proposals

A solar proposal is worth comparing only when each installer is responding to the same home, electricity-use history, and goals. Before choosing the lowest price or monthly payment, line up the system design, what work is included, the ownership terms, and the conditions that could change the scope. Choose the proposal that explains those assumptions in writing and lets you compare the same job—not the one that makes the broadest production or savings claim.

This guide is for a homeowner who has two or more rooftop-solar proposals and needs to decide whether they describe comparable work. The practical answer is to request the same information from every installer, then mark each item included, excluded, or unresolved. Your next action is to send the checklist below with your electricity-use records and ask for written answers before signing.

Begin with the same starting information

Give every installer the same recent electricity-use history, any expected changes such as an electric vehicle or heat pump, and the same visible information about your roof and electrical equipment. Do not climb on the roof or open an electrical panel. Ask each installer to identify any site visit, roof review, structural review, or electrical assessment still needed. The U.S. Department of Energy (DOE) advises homeowners to consider electricity needs, site conditions, and financing options before selecting a system.

A proposal is an offer based on stated assumptions; it is not a guarantee of yearly production, utility savings, incentive eligibility, or future electricity rates. If two proposals use different annual-use figures, roof layouts, or utility assumptions, ask the installers to revise them to a shared basis before comparing price.

Put each proposal on one comparison sheet

Use the same sheet for every proposal. A blank field is useful information: it means you need a written answer rather than an assumption.

Item to compare	What the written proposal should say
System design and production	System size in kilowatts (kW), panel count and model, planned roof areas, shading or production assumptions, and any expected annual output. Ask what data or site condition could change the design.
Equipment	Panel, inverter, racking, rapid-shutdown, monitoring, and—if offered—battery model numbers. Do not treat a brand name alone as a complete equipment description.
Roof and electrical scope	Attachment and flashing approach, roof-condition assumptions, panel or service work, trenching, upgrades, and who evaluates conditions that are outside the installer’s scope.
Permits and utility process	Which permits, plans, inspections, interconnection steps, and utility applications the installer handles; listed fees; and who responds if an authority or utility requires a correction.
Ownership and payment	Cash price, loan total and fees, or lease/PPA payment terms; who owns the equipment; escalation or prepayment terms; and what happens if you sell the home.
Warranties and monitoring	Manufacturer and labor coverage, registration duties, monitoring access, service contact, and whether roof-work coordination affects any coverage.
Schedule and access	Expected milestones, access needs, equipment delivery, protection and cleanup, and what can delay installation or permission to operate.
Exclusions and changes	Work specifically excluded, conditions that trigger added cost, who can authorize a change order, and how the revised price is documented before work starts.

Compare total obligations, not just a monthly number

A cash purchase, loan, lease, and power purchase agreement (PPA) are different arrangements. With a lease or PPA, the homeowner generally pays for use of the solar electricity while another party may own the equipment. A lower monthly amount does not by itself show a lower total cost or a better fit. Ask for the full payment schedule, fees, escalation language, end-of-term options, transfer process, and any conditions that affect a sale or refinance.

Incentives, utility credits, and tax treatment can change and may depend on eligibility, location, and timing. DOE directs homeowners to current federal, state, and local resources, but an installer projection or a database listing is not proof that you qualify. Confirm current terms with the relevant program administrator and seek qualified tax advice when tax treatment matters.

Resolve differences before selecting an installer

Do not average unlike proposals. If one proposal includes electrical work, roof coordination, permit fees, or a battery and another does not, ask both installers to separate base scope, options, and conditional work. If their production figures differ, ask each to explain the data, assumptions, and limitations in plain language. For a battery proposal, confirm the specific loads it is designed to support and how the system behaves during a grid outage; solar panels alone do not automatically provide backup power.

Keep the final proposal, change orders, equipment list, permit records, and warranty instructions together. A clear paper trail makes it easier to compare scopes now and to understand responsibilities later.

Questions to ask your solar installer

1. Which electricity-use, shading, roof, and utility assumptions support this system size and annual-production estimate, and what would cause them to change?
2. What roof, electrical, permitting, interconnection, and monitoring work is included, excluded, or conditional in this price?
3. If a site condition changes the scope, how will you present options and obtain my written approval before extra work begins?

Before requesting revisions, use How to prepare for rooftop solar to organize your project information. For a broader cost and ownership review, read How much should solar panels cost?. If storage is included, compare the backup plan in Solar panels vs. solar plus battery storage.

Sources

• U.S. Department of Energy: Homeowner’s Guide to Going Solar (accessed October 1, 2026).
• U.S. Department of Energy: Solar Energy Resources for Consumers (accessed October 1, 2026).

Be ready for the conversation

3 questions to ask your solar installer

1. 1What simple maintenance is safe for me to handle myself?
2. 2What should I take a photo of or keep an eye on before I call you?
3. 3What warning sign means I should call for help right away?