A solar quote is only comparable with another quote when both cover the same job. A low total may exclude roof work, an electrical upgrade, storage or required approval steps. Start by making the scope visible.
Put equipment and work on separate lines
Record the panel and inverter identifiers, array size, storage if included and the proposed mounting arrangement. Then list design, applications, installation, inspection, commissioning and any preparatory work. Ask whether taxes and delivery are included. Mark allowances that could change after a site visit.
Keep battery power and energy capacity separate. A proposal with storage is not a like-for-like comparison with a proposal without it.
Examine the output estimate
Ask for the assumptions behind expected generation: site location, orientation, shading and modeled losses. Request a monthly profile as well as an annual total. Two proposals can use similar equipment yet assume different site conditions.
The Department of Energy homeowner guide identifies electricity consumption, system production and utility compensation as factors affecting savings. Its page includes historical policy material, so do not use old tax-credit statements as current eligibility advice. Verify any incentive directly with the administering authority at the time of your decision.
Use your own bill and a labeled scenario
If you compare projected operating costs, state the tariff and consumption assumptions. Separate electricity used on site from electricity exported. A single retail-rate multiplication can misrepresent a project if exported energy receives a different credit.
A simple comparison can show three scenarios: the quoted assumptions, less favorable production and changed consumption. These are sensitivity checks, not promises about future prices or returns.
Include the later questions
Ask who monitors faults, who handles warranty claims and whether labor, access and transport are covered. Clarify responsibilities if the original installer stops trading. Keep maintenance assumptions visible rather than silently treating future ownership as free.
Choose on an equal basis
Before accepting a proposal, reconcile exclusions and unresolved site conditions in writing. An itemized quote is useful even when its total is higher because it reveals what you are buying. Our planning checklist helps define that scope. We do not publish universal savings guarantees or individualized financial advice.