Inputs
Example data
Use this table as a starting point, then replace with your site values.
| PV kW | Annual kWh | Baseline % | Target % | Battery kWh | Cycles/day | Retail price | Export price |
|---|---|---|---|---|---|---|---|
| 50 | 80,000 | 8 | 2 | 80 | 0.6 | 0.18 | 0.11 |
| 250 | 410,000 | 12 | 4 | 300 | 0.8 | 0.16 | 0.08 |
| 10 | 15,000 | 5 | 1 | 10 | 0.4 | 0.22 | 0.12 |
Tip: If you do not have a battery, set battery capacity to 0.
Formula used
- Baseline curtailed energy:
BaselineCurt = AnnualProduction × (BaselineCurt% ÷ 100) - Target curtailed energy:
TargetCurt = AnnualProduction × (TargetCurt% ÷ 100) - Theoretical reduction:
ReductionTheoretical = max(0, BaselineCurt − TargetCurt) - Battery capture capacity:
BatteryCap = BatterykWh × CyclesPerDay × 365 × RoundTripEff - Estimated recoverable energy:
Recoverable = min(ReductionTheoretical, min(BaselineCurt, BatteryCap) × (1 + Gains%)) - Recovered value:
Value = (Recoverable×SelfShare×RetailPrice) + (Recoverable×(1−SelfShare)×ExportPrice) - NPV:
NPV = −Capex + Σ(NetAnnualBenefit ÷ (1 + r)^t)
These equations are simplified and are best used for planning and comparison.
How to use this calculator
- Enter your annual PV production and current curtailment percentage.
- Set a realistic target curtailment after upgrades or controls.
- If using storage, enter battery size, efficiency, and expected cycling.
- Choose how much recovered energy is used onsite versus exported.
- Add prices, costs, and analysis settings to see payback and NPV.
- Click Calculate, then download CSV or PDF if needed.
Curtailment as a measurable loss
PV curtailment occurs when available solar generation is intentionally reduced because of export limits, voltage constraints, congestion, or operational rules. This calculator converts that operational issue into annual kilowatt-hours, so you can compare sites, seasons, and mitigation options. Start with annual production and a baseline curtailment percentage. The resulting curtailed energy represents value you are already paying to produce, but not capturing.
Drivers and controllable levers
Not all curtailment is fixed. Storage can absorb surplus energy during constrained hours and release it later. Smart controls can shift flexible loads, schedule charging, and reduce clipping by improving dispatch. Inverter upgrades or firmware changes may widen operating envelopes or improve ramping behavior. In this model, controls and inverter improvements are represented as a gain applied to the captured portion, helping you test conservative scenarios.
Estimating recoverable energy
Recoverable energy is bounded by two constraints: the theoretical reduction between baseline and target curtailment, and the practical capture capacity of the chosen solution. Battery capture capacity is estimated from battery size, expected cycles per day, and round-trip efficiency. The calculator then limits recovery to what storage can realistically cycle each year and applies your gains. Output is split into onsite and exported kilowatt-hours for valuation.
Valuing recovered kilowatt-hours
Each recovered kilowatt-hour is priced based on where it is used. Onsite consumption is valued at the retail electricity price, while exported energy is valued at the export compensation rate. By adjusting the self-consumption share, you can explore how adding flexible loads or improving demand alignment increases value. Annual O&M is subtracted to compute net annual benefit, creating a consistent yearly cashflow estimate.
Interpreting payback and NPV
Simple payback divides investment cost by net annual benefit, which is intuitive but ignores timing. Net present value discounts benefits over the selected analysis period using your discount rate, enabling comparisons across projects with different lifetimes and risk profiles. If NPV is positive and payback matches your requirements, curtailment reduction can be an upgrade. Use the chart to sanity-check magnitudes before relying on the decision confidently.
FAQs
1) What is PV curtailment in practical terms?
It is generation your system could produce but is reduced by grid or equipment constraints. Common causes include export caps, voltage rise, inverter clipping, or utility dispatch requirements.
2) Why does storage help reduce curtailment?
A battery can capture surplus energy during constrained hours and deliver it later when export or onsite demand allows. The model estimates capture using battery size, cycling, and efficiency.
3) How should I choose self-consumption share?
Use measured load data if available. If you plan to add flexible loads like EV charging or cooling, increase the share to reflect more onsite use of recovered energy.
4) What do the gain inputs represent?
They represent incremental recovery from better dispatch, controls, or inverter improvements beyond storage alone. Use modest values for conservative cases and higher values only with evidence.
5) Does the export limit directly change the math?
Export limit provides context because it often drives curtailment, but hourly shapes matter. Use baseline and target curtailment percentages to reflect the effective outcome of the constraint.
6) How accurate are the results?
This is a planning tool. Accuracy depends on hourly production and load profiles, control strategy, and interconnection rules. Validate with interval data or a detailed simulation before investing.