| Scenario | System (kW) | Sun Hours | Perf. Ratio | Rate | Self-use % | Export Rate | Net Savings (Year 1) |
|---|---|---|---|---|---|---|---|
| Warehouse roof | 30 | 5.2 | 0.80 | 0.17 | 85 | 0.12 | ≈ 7,300 |
| Site office | 8 | 5.0 | 0.82 | 0.18 | 75 | 0.18 | ≈ 1,900 |
| Remote compound | 15 | 4.6 | 0.78 | 0.22 | 65 | 0.10 | ≈ 2,400 |
- Annual generation (kWh):
System Size (kW) × Peak Sun Hours × 365 × Performance Ratio - Self-used energy (kWh):
min(Annual Generation × Self‑consumption %, Annual Load) - Exported energy (kWh):
max(Annual Generation − Self‑used, 0) - Gross savings:
Self‑used × Electricity Rate + Exported × Export Rate - Net annual savings:
Gross savings − Annual Maintenance Cost - CO₂ avoided (t/yr):
(Annual Generation × CO₂ factor) ÷ 1000
- Enter the installed system size and the site’s average peak sun hours.
- Use a realistic performance ratio to account for real-world losses.
- Provide your electricity rate, annual load, and an estimated self-consumption percentage.
- Set the export credit rate and maintenance cost based on your operations plan.
- Click Calculate Savings to view results above the form.
- Use Download CSV or Download PDF to save your report.
Project energy yield assumptions
Annual output drives the value of a solar investment on construction sites, warehouses, and temporary facilities. Use peak sun hours from local solar maps or measured irradiance. Apply a performance ratio that reflects inverter efficiency, temperature losses, cable losses, dust, and downtime. A realistic ratio commonly sits between 0.75 and 0.90, depending on maintenance practices and the operating environment. Document assumptions for audits and client reporting, including commissioning notes and photos.
Tariff, export credits, and self-consumption
Financial benefit is split between energy consumed on-site and energy exported. When export credits are lower than the retail tariff, improving self-consumption increases savings. Strategies include shifting loads to daylight hours, scheduling pumping and batching, or adding storage. If net metering is available, exports may receive near-retail value, reducing the penalty of exporting.
Operations, maintenance, and reliability
Maintenance costs should include periodic cleaning, inspection of mounting hardware, inverter monitoring, and minor replacements. Dirty modules can reduce production significantly in dusty environments. For construction projects, plan safe access and cleaning frequency, and track inverter alarms to limit downtime and protect annual savings estimates.
Degradation and escalation for long-term planning
Panel output typically declines each year, while electricity prices often rise. This calculator applies annual degradation to generation and escalation to rates for an indicative multi‑year savings view. Use conservative escalation when budgeting and compare scenarios with different degradation rates to understand risk and sensitivity.
Example data and interpretation
Example inputs: System size 12 kW, peak sun hours 5.1, performance ratio 0.83, electricity rate 0.20 per kWh, annual load 14,000 kWh, self-consumption 80%, export rate 0.12, maintenance 200 per year. Typical result: about 18,500 kWh/year generation and roughly 3,000 net annual savings, depending on exports and credits. Use this example to validate data entry and align assumptions with site operations.
FAQs
1) What is the performance ratio and why does it matter?
It captures real-world losses from heat, wiring, inverter efficiency, shading, and soiling. A realistic value prevents overstated generation and keeps savings estimates aligned with operational performance.
2) How do I estimate peak sun hours for my site?
Use location-based solar resource data, local PV studies, or measured irradiance. If uncertain, start with a conservative average and run multiple scenarios to bracket expected output.
3) Why does self-consumption affect savings so much?
Self-used energy offsets the full retail tariff. Exported energy may be credited at a lower rate, so a higher self-consumption percentage usually increases net savings.
4) What export credit rate should I use?
Use your utility’s export tariff or contract value. If net metering credits exports near the retail rate, use a similar value; otherwise use the stated buyback credit.
5) Does the calculator include battery storage impacts?
Not directly. You can approximate storage by increasing self-consumption percentage and adding storage-related maintenance costs, then compare scenarios to gauge financial sensitivity.
6) How should I set degradation and escalation values?
Use conservative assumptions for budgeting. Typical degradation is under 1% per year, while escalation depends on market conditions and contract terms. Run low, base, and high cases.
7) Can annual generation exceed my annual load?
Yes. In that case, the extra energy is treated as exported. The export credit rate determines how valuable that excess production is compared with on-site consumption.