A professional proposal should explain how the system was sized, what equipment is supplied, how safety and approvals will be handled and who supports the plant after commissioning. Asking consistent questions makes competing quotations easier to compare.
Key takeaways
- Request a clear load, roof and generation basis.
- Demand exact make and model details.
- Separate product, performance and workmanship warranties.
- Confirm approvals, tests, documents and service response.
Sizing and energy questions
Ask which electricity bills and load data were used, how daytime self-consumption was estimated and why the proposed capacity is appropriate. Request monthly generation estimates with irradiation, performance ratio, shade and degradation assumptions. A proposal should explain export treatment and not guarantee a bill of zero.
- What consumption period was analysed?
- What shade and roof survey was completed?
- What monthly generation is expected?
- How much energy is expected to be self-consumed?
Equipment and design questions
Obtain exact module, inverter, structure, cable, connector and protection models. Ask for the string design, single-line diagram, mounting method and corrosion protection. For hybrid projects, request usable battery energy, backup load schedule, operating modes and compatible BMS details.
- Are model numbers fixed in the quotation?
- Are inverter voltage and current limits documented?
- What AC/DC protection and earthing are included?
- How is roof waterproofing protected?
Warranty and service questions
Product warranties, module performance warranties and installer workmanship warranties are different. Ask who submits claims, whether labour and transport are included, expected service response and what monitoring the owner receives. Verify that promised warranty terms match manufacturer documents.
- Who is the first service contact?
- What is excluded from warranty?
- Is replacement labour chargeable?
- Who owns the monitoring account and data?
Approvals, commissioning and commercial clarity
Confirm responsibility for utility applications, metering, subsidy documentation, inspection and any excluded charges. Request a payment schedule linked to milestones and an itemised scope. Before final payment, obtain commissioning results, approvals, as-built documents and owner training.
- Which approval fees are included?
- Is subsidy guaranteed or only assisted?
- What tests are completed before energisation?
- What documents are delivered at handover?
Frequently asked questions
Should I choose the lowest solar quotation?
Compare scope, equipment, engineering, safety, approvals, warranty and service. A lower price may exclude essential work.
Can an installer guarantee generation?
They can provide a model and performance commitment with stated assumptions, but weather and site conditions create variability.
What should be fixed before ordering?
Confirm capacity, model numbers, scope, exclusions, layout, commercial terms, approvals, warranty and completion milestones.
Turn guidance into a practical system plan
Use Spectra’s engineering calculators for a preliminary estimate, then request technical verification before purchase or installation.