Comparing solar installation quotes is easier when every proposal is translated into the same set of numbers, equipment details, responsibilities, and contract terms. This checklist shows how to review a home solar system proposal line by line, estimate the value of each offer, and identify questions to resolve before signing.
Overview
A solar quote is more than a price for solar panels. It is a plan for producing electricity, connecting equipment to your home, obtaining approvals, and supporting the system after installation. Two proposals with similar totals may offer different panel capacities, production estimates, warranties, financing costs, or installation responsibilities.
Start by asking each installer to present the proposal in comparable terms. Record the system’s direct-current capacity, estimated annual production, equipment models, total project cost, and expected payment separately. Do not compare only the headline price or the number of panels. A larger system may produce more electricity but cost more, while a smaller system may be a better fit if your roof, budget, or electricity use is limited.
Use the following comparison table as a starting point:
| Proposal item | What to record | Why it matters |
|---|---|---|
| System size | Panel count and total kW | Shows the planned generating capacity |
| Estimated production | Annual kWh and assumptions | Helps compare expected energy output |
| Panels | Manufacturer, model, power rating, warranty | Confirms exactly what is being offered |
| Inverter equipment | Type, model, capacity, warranty | Affects conversion, monitoring, and replacement planning |
| Price | Cash price, financing total, fees, and incentives | Separates project cost from payment structure |
| Installation scope | Roof work, wiring, labor, permits, and interconnection | Identifies included and excluded responsibilities |
| Support | Workmanship coverage and service process | Clarifies who handles installation problems |
How to estimate and compare solar quotes
1. Normalize the system size
Write down the total system capacity in kilowatts, not just the panel count. Panel count alone can be misleading because panels may have different power ratings. Also record whether the quoted capacity is described as DC, AC, or another measurement. If the proposals use different conventions, ask the installers to explain the difference before comparing them.
For a simple comparison, calculate the quoted cost per watt:
Cost per watt = project cost before financing divided by system capacity in watts
Use this as a screening tool rather than a final judgment. A quote with a higher cost per watt may include difficult roof access, electrical upgrades, a battery, or additional work that another proposal omits.
2. Compare production, not promises
Record the estimated annual electricity production in kilowatt-hours. Ask what assumptions produced that estimate, including roof orientation, shading, weather data, system losses, and expected degradation. Request a layout showing panel locations if shading or roof design affects the calculation.
Compare production relative to system size:
Estimated production per installed kW = annual estimated kWh divided by system size in kW
This calculation can reveal when one proposal assumes notably different site conditions. It does not prove that one installer is correct, but it gives you a focused question: “Why does this proposal forecast more or less production from a similarly sized system?”
3. Separate equipment from installation scope
For every proposal, identify the exact solar panel model, inverter or microinverter model, racking system, monitoring equipment, disconnects, and other major components. The quote should state whether equipment is new and whether substitutions require your approval.
Then check the installation scope. Look for roof attachment and flashing work, conduit routes, main-panel changes, structural review, tree or shade work, system monitoring setup, cleanup, and removal of existing equipment. Ask what happens if the installer discovers damaged roofing or an electrical issue. A clear change-order process is more useful than a vague promise that “standard installation” is included.
4. Review the total financial commitment
Request both the cash price and the complete financed cost, if financing is offered. Record the deposit, loan amount, interest rate or equivalent financing charge, payment schedule, term, prepayment conditions, and any fees. Confirm whether the quoted payment assumes an incentive, a future lump-sum payment, or a particular utility outcome.
Keep incentives separate from the installer’s price. Rules for tax credits, rebates, and other programs can depend on location, eligibility, timing, and current regulations. Treat any incentive as an assumption to verify rather than money guaranteed by the quote. A qualified tax or financial professional can help determine how a particular incentive applies to your situation.
5. Check warranties and service responsibilities
Review product warranties for panels, inverters, batteries, and monitoring hardware separately from the installer’s workmanship warranty. Note the coverage period, remedy offered, exclusions, labor coverage, shipping responsibility, and claim process. A manufacturer warranty may cover a component but not the labor needed to diagnose or replace it.
Ask who you contact if the system stops communicating, produces less than expected, leaks at a roof attachment, or trips an electrical device. The contract should identify the responsible party and explain how service requests are handled. Avoid relying on a verbal statement that is absent from the proposal or contract.
Inputs and assumptions to verify
Before choosing a proposal, build a short assumptions list. Include your recent electricity use, utility rate structure, planned changes such as an electric vehicle or heat pump, roof age and condition, available roof area, shading, and whether backup power is a requirement. A home solar system designed around unusually low recent usage may be undersized if major electric loads are added later.
Ask each installer these practical questions:
- What annual electricity use was used for system sizing?
- What roof areas are included, and which areas were excluded?
- How were shade and system losses modeled?
- Does the proposal include permits, inspections, utility interconnection, and application fees?
- What work is excluded, such as roof repairs, service-panel upgrades, trenching, or tree removal?
- Can the system be expanded later, and what limits the expansion?
- Does a battery provide whole-home backup or only selected-load backup?
- What equipment controls battery charging, backup operation, and monitoring?
- What events allow the installer to change the price or equipment?
For battery proposals, record usable capacity, power output, backup circuits, operating mode, installation location, and warranty conditions. A battery priced into a quote may be intended for energy shifting rather than outage backup. Compare the function you need, not only the storage capacity.
You can use the site’s home solar system sizing guide to organize usage and system-size assumptions. For a broader view of potential project economics, see the solar panel cost calculator guide.
Worked examples
Example 1: Similar prices, different systems
Imagine Proposal A offers a 7 kW system for a cash price of $21,000, while Proposal B offers an 8 kW system for $23,200. Proposal A costs $3.00 per watt; Proposal B costs $2.90 per watt. That calculation makes Proposal B appear less expensive per unit of capacity, but it does not settle the decision. Compare each proposal’s estimated annual production, roof work, inverter design, warranty terms, and included electrical work.
If Proposal B excludes a service-panel upgrade that Proposal A includes, the apparent difference may disappear after the missing work is priced. Add every required cost before deciding.
Example 2: Cash versus financed purchase
Suppose an installer presents a cash price and a loan option with a lower monthly payment. Write down the total of all scheduled loan payments, plus any fees or required lump-sum payments. Compare that figure with the cash price and with your expected electricity savings using conservative assumptions. Do not treat a monthly payment as the project cost.
Fill-in proposal worksheet
Copy this worksheet for each installer:
- Installer and proposal date:
- System size and panel count:
- Panel manufacturer and model:
- Inverter type and model:
- Battery model, usable capacity, and backup scope:
- Estimated annual production:
- Cash price before incentives:
- Financed amount, fees, term, and total scheduled payments:
- Included permits, inspections, interconnection, and labor:
- Excluded work and change-order terms:
- Product, battery, and workmanship warranty details:
- Expected installation timeline and cancellation rights:
- Questions requiring written answers:
When to recalculate and revisit the quote
Recheck your comparison whenever a major input changes. This includes a revised electricity bill, a new utility rate structure, a roof replacement, an added electric vehicle or heat pump, a battery upgrade, a financing change, or a revised equipment list. Recalculate when an incentive or program rule changes, and verify the current terms rather than carrying an old assumption into a new contract.
Also revisit the proposal if the installer changes the design after a site survey, inspection, or utility review. Confirm the new system size, production estimate, price, equipment, and completion responsibilities in writing. If the contract contains an escalation clause, identify what can trigger an increase, how notice is provided, and whether you can cancel before paying the revised amount.
Before signing, place every proposal on one comparison sheet, mark unanswered items, and request written clarification. Choose the offer that remains understandable after all costs, assumptions, equipment, warranties, and exclusions are included—not simply the one with the lowest advertised price. Keep the worksheet with your contract so you can use it later when checking installation completion, monitoring system performance, or evaluating a solar battery addition.
