A commercial or industrial solar system is a significant capital investment. Proposals from different installers can look very different, which makes them hard to compare. Some are detailed engineering documents; others are a price and a system size on one page.
This guide sets out what a complete proposal should contain, so you can compare like with like and spot the gaps before you sign.
1. Load data and site assessment
The proposal should show that the installer understands how your site uses power.
- Measured load profile. Ideally logged over at least a week, showing demand by hour. Estimates from nameplates alone often overstate or understate real use.
- Critical loads identified. Which equipment must never lose power, and which can be shed.
- Current energy costs. Grid bills, diesel consumption and generator run-hours, taken from your records.
- Site survey findings. Roof condition and structure, available land, shading, cable routes, and the condition of your existing switchgear and earthing.
Red flag: a system size quoted before anyone has visited the site or looked at your bills.
2. System design
- System type and reasoning. Hybrid, off-grid or grid-tied, and why. For most Nigerian sites with generators, this will be hybrid. Our inverters guide explains the difference.
- Solar array size in kWp, with the layout on roof or ground.
- Battery capacity in usable kWh, with the depth of discharge assumed and the backup time it gives for your critical loads.
- Inverter capacity in kW, matched to peak and surge loads.
- Generator integration. How and when the generator starts, and how the system avoids running it unnecessarily.
- Single-line diagram showing how the system connects to your existing distribution, with protection devices.
- Structural considerations for rooftop systems, including whether a structural check is needed.
3. Equipment
Every major component should be named: manufacturer, model and quantity.
| Component | What to check |
|---|---|
| Solar panels | Manufacturer, model, wattage, datasheet, product and performance warranties |
| Inverters | Model, continuous and surge rating, number of units, datasheet, warranty |
| Batteries | Chemistry, usable capacity, cycle rating at the stated depth of discharge, warranty |
| Mounting | Material and corrosion protection, suitability for your roof type or ground conditions |
| Protection | DC and AC isolators, surge protection, earthing and lightning protection |
| Cabling | Sizes and type suitable for outdoor and DC use |
| Monitoring | What is monitored, and who can see the data |
Red flag: “Tier 1 panels” or “premium batteries” without a named make and model. You cannot check a warranty on equipment that is not named.
4. Energy yield estimate
The proposal should estimate how much energy the system will produce each year, and how much of your consumption it will cover.
- What solar resource data was used for your location.
- What losses were assumed: heat, dust, shading, cabling and inverter efficiency.
- How much generator and grid energy the system is expected to replace.
- How output varies by season, including harmattan dust and the rainy season.
5. Financial model
A credible payback model is transparent. You should be able to change an assumption and see the effect.
- Total installed cost, broken down by major item.
- Annual savings, split into diesel, generator servicing and grid energy.
- Key assumptions: diesel price, grid tariff, annual price increases, generator hours, system degradation.
- Future costs: maintenance and battery replacement within the analysis period.
- Simple payback and, for larger projects, a cash-flow view over the life of the system.
Our solar versus generator guide shows how simple payback is calculated, so you can check the arithmetic.
Red flag: a single savings percentage or payback figure with no workings behind it.
6. Delivery plan
- Timeline for procurement, installation and commissioning.
- Equipment lead times and what happens if items are delayed.
- Impact on operations. Planned shutdowns for connection work, and how they will be scheduled around your business.
- Site safety. How work at height and electrical work will be managed.
- Commissioning and testing. What tests will be performed, and the documents you will receive at handover.
7. Commercial terms
- Payment schedule. Whether payment is staged against milestones, upfront with a balance, or financed. Check what triggers each payment.
- Warranties. Manufacturer warranties for each component, and the installer’s workmanship cover, with what each covers and how claims are handled.
- Performance commitments, if any, and how they are measured.
- Responsibilities. Who obtains any approvals, who insures the equipment during installation, and who is responsible for roof repairs if needed.
8. Operation and maintenance
- Maintenance schedule: panel cleaning, inspections, battery and inverter checks.
- Response times for faults, in writing.
- Monitoring. Who watches system performance and how problems are reported.
- Training for your staff on basic operation and safety.
- Cost of the maintenance agreement after any included period.
A comparison checklist
Use this to score proposals side by side. A strong proposal has all twelve:
- Based on measured load data and a site visit
- Critical loads identified
- Single-line diagram included
- Every major component named, with datasheets
- Usable battery capacity and backup time stated
- Generator integration explained
- Energy yield estimate with stated losses
- Payback model with all assumptions visible
- Timeline and planned shutdowns set out
- Payment schedule tied to clear milestones
- Manufacturer and workmanship warranties described
- Maintenance plan and response times in writing
The cheapest proposal is often the one with the most gaps. A proposal that ticks every box is easier to hold to account.
If you want a proposal built this way for your site, our commercial and industrial solar service starts with an energy audit of your own records.
Updated
