Base annual energy: Ebase = System(kW) × Yield(kWh/kW)
Without optimizers: Eno = Ebase × (1 − ShadingLossno)
With optimizers: Eopt = Ebase × (1 − ShadingLossopt) × (1 + Gain) × (1 + Uptime)
Incremental energy: ΔE = Eopt − Eno
Year y adjustments: ΔEy = ΔE × (1 − Degradation)y−1
Tariff escalation: Ratey = Rate × (1 + Escalation)y−1
Net cashflow: CFy = (ΔEy × Ratey) − Maintenance
NPV: NPV = Σ CFt / (1 + Discount)t, with CF0 = −NetCAPEX
IRR: the rate r where NPV(r) = 0 (bisection search).
ROI: ROI = (TotalNetBenefits − NetCAPEX) / NetCAPEX × 100
- Enter system size and expected annual yield per kW.
- Set your electricity rate and expected yearly escalation.
- Enter optimizer pricing, labor, incentives, and maintenance.
- Adjust shading losses to reflect site conditions.
- Choose a discount rate aligned with project risk.
- Press Calculate ROI to view KPIs above the form.
- Download CSV or PDF for proposals and internal reviews.
For commercial projects, consider using measured interval data and separate O&M budgets.
These sample rows illustrate typical output fields. Your results will update after calculation.
| Year | Incremental kWh | Rate ($/kWh) | Incremental Value ($) | Maintenance ($) | Net Cashflow ($) | Discounted Net ($) | Cumulative Net ($) |
|---|---|---|---|---|---|---|---|
| 1 | 1,120 | 0.1800 | 201.60 | 20.00 | 181.60 | 171.32 | -1,498.40 |
| 2 | 1,114 | 0.1845 | 205.55 | 20.00 | 185.55 | 165.00 | -1,312.85 |
| 3 | 1,108 | 0.1891 | 209.52 | 20.00 | 189.52 | 159.01 | -1,123.33 |
Example values are illustrative and not tied to a specific site.
Why optimizer ROI matters in construction energy planning
Solar optimizers can improve energy harvest where module mismatch, partial shading, or complex roof geometry reduces production. For construction teams, the key question is whether added component and labor costs translate into measurable utility savings. This calculator isolates the incremental benefit by comparing shaded output without optimizers to improved output with optimizers, then valuing the difference using your tariff assumptions.
Inputs that drive incremental kWh the most
Three fields typically dominate the energy lift: shading loss without optimizers, shading loss with optimizers, and annual production per kW. Shading loss captures tree lines, parapets, HVAC equipment, and setbacks. Production per kW reflects climate, tilt, azimuth, and local irradiance. Monitoring uptime gain represents faster fault detection and reduced downtime from string issues or connector failures.
How the cashflow model supports budget reviews
The model converts incremental kWh into annual dollar value using the electricity rate and escalation. PV degradation reduces incremental kWh each year, while discount rate converts future savings into present value for finance review. Net cashflow subtracts annual maintenance, producing a year-by-year table that is easy to compare against capital allowances and payback policies.
Interpreting ROI, NPV, and IRR correctly
ROI summarizes total net benefits relative to net optimizer CAPEX over the selected period. NPV shows the discounted value of all cashflows, which is useful when comparing alternatives with different lifetimes. IRR estimates the implied return rate where NPV equals zero; if cashflows never cross zero, IRR may be unavailable within the tested range.
Practical guidance for realistic assumptions
Use site shading studies or measured production data when available, and keep shading improvements conservative. Confirm optimizer pricing from current vendor quotes and include any incremental wiring or commissioning time in labor. If incentives apply to the full PV system rather than optimizers alone, enter only the portion that reduces optimizer-related cost. Export CSV for stakeholder review and attach the PDF summary to internal approval packages.
1) What does this calculator measure?
It estimates the incremental financial return from adding optimizers by valuing extra energy produced versus a no-optimizer case, then computing payback, ROI, NPV, and IRR using your cost and tariff inputs.
2) Should I use DC or AC system size?
Use the DC nameplate size that matches your production per kW assumption. If your yield is based on AC capacity, convert it so system size and yield are on the same basis.
3) Why are there two shading loss inputs?
They represent expected loss without optimizers and the reduced loss with optimizers. The difference drives incremental kWh, so keep values realistic and consistent with your roof layout.
4) What discount rate should I use?
Use your organization’s hurdle rate or weighted cost of capital for capital projects. Higher discount rates reduce NPV and may lengthen perceived payback for the same savings.
5) Why might IRR show “n/a”?
IRR requires cashflows to cross zero. If net savings never recover the upfront cost within the analysis period, or if values stay on one side of zero, a valid IRR may not exist.
6) Can I use this for proposal documentation?
Yes. Use the CSV for detailed review and the PDF for a concise summary. For formal bids, attach supporting assumptions such as shading analysis, tariff documentation, and vendor quotes.