Quick answer
Simulation of energy reduction from specified operating restrictions using defined generation, load, export and control inputs; model boundaries and assumptions determine the result.
Answer: Curtailment modeling estimates the energy reduction caused by a specified operating constraint by comparing otherwise equivalent unrestricted and restricted scenarios. A simple export-limit model uses synchronized PV generation, site load and permitted export profiles at a common electrical boundary. Storage, dynamic limits, voltage controls and dispatch rules need additional logic. Results depend on input quality and time resolution; a model is not a guaranteed production or revenue forecast.
Start with a defined constraint
Curtailment is the operating phenomenon; modeling is the calculation workflow used to estimate its effect. State whether the modeled restriction applies to inverter output, net export at the connection point or a plant dispatch instruction. A limit in kW is active power; kVA is apparent power. They are not interchangeable without the operating conditions.
PVsyst’s grid power limitation documentation describes a specific implementation. The documentation distinguishes inverter and injection-point limits and notes complications when attributing losses with storage. Check the documentation for the actual software version and topology. A feature label does not prove distribution-network voltage modeling or unrestricted battery dispatch capabilities.
Inputs and provenance
| Input | Required context |
|---|---|
| Available PV output | AC or DC boundary, modeled losses, weather file and time step |
| Site load | Matching timestamps, units, missing-data treatment and measured or assumed status |
| Export allowance | Utility agreement, measurement point, fixed or time-varying limit |
| Storage | Usable energy boundary, charge power, starting state, reserve, efficiency and strategy |
| Other controls | Actual dispatch, voltage or ramp-rate behavior and evidence supporting assumptions |
| Financial terms | Relevant import/export prices, compensation and cost boundaries |
Use aligned time zones and daylight-saving conventions. Annual consumption or monthly bills cannot establish when on-site load coincides with PV generation. Historical operator events are evidence for scenarios, not certainty about future events.
A simple export-limit calculation
For a no-storage case at a common AC boundary, define available PV power G, site load L and allowed export X, all in kW. Under the assumed effective control, curtailed power is max(0, G − L − X). Energy for an interval is that power multiplied by its duration in hours.
With G = 6.2 kW, L = 1.8 kW and X = 3.0 kW, the curtailed power is 1.4 kW. At constant values over one hour, loss is 1.4 kWh; over 15 minutes, it is 0.35 kWh. Summing interval energy gives the modeled total. The simplified equation does not represent transient controller overshoot, voltage trips or storage operation.
Time resolution can change the answer
Consider two hypothetical half-hour intervals with zero site load and a 3 kW export cap. Available PV powers are 6 kW and 0 kW. Interval modeling gives (6 − 3) × 0.5 = 1.5 kWh curtailed. Averaging to 3 kW across the hour before applying the cap gives zero modeled curtailment. This illustrates why applying a nonlinear limit to averaged inputs can conceal events; it is not a universal error percentage.
Select resolution for the question and input quality. Hourly energy modeling does not establish compliance with a fast control-response requirement. Distribution voltage studies need suitable network information and control models, not merely an annual PV curve.
Add storage without double counting
At each step, respect charging power, remaining usable capacity, reserve, topology and dispatch priorities. Record PV energy used directly, exported, stored and curtailed separately. Account for charging and discharging losses at the declared boundaries. Energy stored during a formerly constrained interval is not automatically equal to useful energy delivered later.
Compare the same baseline without and with the constraint. Preserve other losses and equipment assumptions, and keep inverter clipping distinct. Do not subtract an export loss factor again if the simulation already incorporated it.
Turn scenarios into a decision
Compare candidate PV sizes, load schedules, export limits and storage configurations using consistent weather and cost assumptions. Lower curtailment alone does not establish the best financial design. Use interval prices in the financial model, plus relevant financing, replacements and constraints. A low export tariff is not itself an export cap.
Provide the input sources, model version, revision, baseline, time resolution and sensitivity cases with the result. For a software evaluation, request a sample with a known cap, measured load profile and clearly reported energy balance. Confirm which restrictions and storage modes the demonstrated product actually models.
Common questions
Can monthly consumption accurately locate curtailed intervals?
It cannot establish time coincidence by itself. Use appropriately synchronized interval data or disclose the assumed profile.
Is curtailed power in kW already curtailed energy?
No. Multiply power by the relevant interval duration to obtain kWh.
Does an hourly export model predict voltage-trip behavior?
Not automatically. That requires suitable network data and the relevant control/protection model.
Does the model prove a battery will pay for itself?
No. Financial comparison must include dispatch limits, losses, tariff or contract value and storage costs.
Related Glossary Terms
About the Contributors
Editorial contributor · SurgePV
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CEO & Co-Founder · SurgePV
Keyur Rakholiya is identified by SurgePV as its CEO and a company co-founder. His SurgePV author page lists only role information that can be tied to the public profile below; credentials, project totals, testing claims, media appearances, and speaking engagements are not asserted without retained evidence.
