By Vvon Engineering Team | Published | Updated
A practical guide to site-specific solar ROI: measured demand, generation assumptions, current costs, utility approval, warranties and downside scenarios.
Solar EPC & street lighting RFQ checklist (TXT)
A rooftop solar investment needs a site-specific comparison of generation, self-consumption, export credit, installed cost and ongoing expenses. This guide explains the inputs to a financial model and the evidence to request before committing capital.
Use the site's current tariff and a dated installed quotation. Model tariff changes as scenarios rather than forecasts. Module purchase price alone omits mounting, cables, protection, roof work, approvals and service costs. Confirm current net-metering conditions with the utility.
Collect twelve months of bills and representative interval demand. Establish the daytime profile from measurement rather than applying a percentage for all factories. Assess feasible AC and DC capacities separately against roof, inverter and utility constraints.
| Input | Evidence needed | Why it matters |
|---|---|---|
| Consumption | Twelve months of bills and representative interval demand | Separates direct use, exports and changing demand. |
| Generation | Location, layout, weather dataset and loss assumptions | Estimates output month by month. |
| Connection | Sanctioned load, transformer and utility requirements | Establishes eligible capacity and approval conditions. |
| Installed cost | Dated itemised quotation and exclusions | Includes roof work, connection and commissioning. |
| Operating cost | Maintenance, insurance and replacement assumptions | Avoids treating later electricity as cost-free. |
A useful model separates technical output from financial value. It should be reproducible from the following records, not presented as an undocumented customer result.
| Model item | Calculation or evidence |
|---|---|
| Direct energy value | Self-consumed kWh × applicable marginal energy tariff. |
| Export value | Credit applied and residual settlement under the agreement. |
| Net operating benefit | Energy and justified demand benefit less maintenance, insurance and other operating cost. |
| Simple payback | Initial project cash outlay divided by representative annual net benefit; unsuitable if cash flows vary materially. |
| Discounted case | Year-by-year cash flow including degradation, replacement, financing, taxes and a stated discount rate. |
| Sensitivity | Lower generation, lower self-consumption, higher cost, delayed operation and changed tariff. |
Do not attribute a tariff or customer return to a named revision or installation without the supporting bill, order and operating records. Recovering initial capital does not remove ongoing cost.
Assess the actual exposure to heat, humidity, salt, chemicals, wind and hail. Specify exact equipment and evidence for those conditions rather than relying on a broad climate label.
Compare the offered JinkoSolar, JA Solar, Canadian Solar or other models using their current datasheets and warranty documents. BloombergNEF tiering concerns manufacturer bankability, not certification of every module or inverter.
Identify the utility from the electricity bill rather than a simplified map. Use its current application checklist and approval sequence, and obtain a project-specific programme. Do not assume all offices use identical forms or response times.
Request a written solar EPC proposal from Vvon with named scope responsibilities, equipment and verifiable references. Confirm specialist design and subcontract responsibilities instead of assuming every activity is performed in house.
Send bills, the site location and roof information to discuss assessment scope, cost and turnaround. Discuss your solar requirements, call +8801805987890 or email info@vvon.com.bd. Confirm the proposed scope and commercial terms in the quotation.
Consult the relevant edition and the documents for the exact equipment and site: SREDA: Net Metering Guidelines and current application documents; IDCOL: renewable-energy lending terms; IEA PVPS: operation and maintenance in different climates; JinkoSolar: model datasheets, certificates, installation manuals and warranties; BloombergNEF: PV module tiering methodology.
Share your application, equipment requirements and procurement timeline. Our engineers can help clarify the configuration and scope for your enquiry.