What verification evidence should show whether SAM loss…

Key Takeaways

• Show the enable checkbox state; retained table values alone do not prove losses were applied.
• Separate constant, time series, and custom period losses because SAM can apply all applicable losses to the same time step.
• Use a sampled nonzero time step to confirm whether the schedule changes the modeled value as expected.
• For PVWatts availability, show both the Edit Losses schedule and the separate Availability loss category to avoid unclear double counting.
• Confirm the loss schedule mode matches the simulation time step, especially for solar or wind models.
• Record missing evidence as unknown instead of treating retained schedule data as proof of enabled losses.

Summary

Verification evidence should separate two facts: whether loss values exist in the SAM data table, and whether the checkbox or option that makes SAM apply those values is enabled. SAM documentation states that time series loss data can remain in the table while the checkbox disables or enables application of those losses; the same pattern is described for custom period losses. SAM Edit Losses

1. The Evidence Must Show the Enable State, Not Only the Table

A screenshot or exported input table showing hourly, subhourly, or custom-period loss values is not enough. SAM says the time series loss checkbox lets a user enable or disable time series losses without deleting the data in the loss table. SAM Edit Losses For custom periods, SAM likewise says the checkbox can enable custom period losses without deleting the loss schedule. SAM Edit Losses

Useful verification evidence should therefore include the Edit Losses window with the relevant enable checkbox visible, the saved model input state for that checkbox if available, and the loss table or custom period schedule. The table proves retained data; the enable state proves whether SAM should apply it.

2. The Evidence Should Identify Which Loss Mechanism Is Being Checked

SAM supports a constant loss, time series losses, and custom period losses in the Edit Losses window. A constant loss applies to all simulation time steps, while time series losses apply to specific time steps. SAM Edit Losses Custom period losses apply to user-defined start and end date-time periods. SAM Edit Losses

A good audit record should label each mechanism separately: constant loss value, time series enable state and table, and custom-period enable state and periods. This matters because SAM applies all losses that apply to the same time step; if a constant loss, a time series loss, and a custom period loss all apply, all three are applied. SAM Edit Losses

3. The Evidence Should Include a Time-Step Test

A reliable check should pick one simulation time step where the schedule contains a nonzero value and compare expected behavior with the output or intermediate result. SAM states that a zero loss creates no adjustment, a 5% loss reduces the value by 5%, and a -5% loss increases the value by 5%. SAM Edit Losses

If the schedule is enabled, the selected time step should reflect the scheduled adjustment, subject to any other losses that also apply. If the schedule is retained but disabled, the table may still contain values, but those values should not be used as enabled time series or custom-period losses. The second sentence is an audit inference from SAM’s documented enable-disable behavior, not a separate SAM guarantee.

4. PVWatts Availability Checks Need Extra Care

For PVWatts system availability, SAM documentation says availability losses reduce output because of maintenance downtime, grid outages, and other operational factors. SAM PVWatts System Design The same page says the Edit Losses window is used to edit system availability losses, with constant losses applying to the entire output and time series losses reducing output in each specified time step. SAM PVWatts System Design

Evidence should also show whether the separate Availability loss category is being used. SAM notes that if system availability losses are specified to represent operating losses, the Availability loss category should be set to zero. SAM PVWatts System Design Without this evidence, reviewers cannot distinguish intended scheduled availability modeling from possible double counting.

5. What a B2B Review Package Should Contain

For procurement, engineering review, or independent model checking, the minimum evidence package should include: the model page and loss type being reviewed, the enable checkbox state, the retained loss values, one sampled affected time step, and any related loss category that could duplicate the same physical loss. This is a recommendation based on SAM’s documented behavior that retained data and enabled losses are not the same thing. SAM Edit Losses

For solar and wind models, evidence should also show that the time-series mode matches the simulation time step, because SAM says Hourly, Subhourly, or Three Hourly modes must be consistent with the simulation time step, and the Three Hourly mode is for Marine Energy models rather than solar or wind hourly or subhourly simulations. SAM Edit Losses

FAQ

Does a populated SAM loss table prove the schedule was enabled?

No. SAM says time series loss data can remain in the loss table while the checkbox enables or disables those losses.

What screenshot is most useful?

A screenshot of the Edit Losses window showing the relevant checkbox state and the associated loss table or custom period schedule.

What is the difference between retained and enabled loss data?

Retained data means the values still exist in the model table; enabled data means the relevant checkbox or option tells SAM to apply them.

Should constant losses be checked separately?

Yes. SAM documents constant loss as a loss applying to all simulation time steps, separate from time series and custom period losses.

Can several loss types apply at once?

Yes. SAM says all losses that apply to a given time step are applied, including constant, time series, and custom period losses when all are applicable.

How can a reviewer test whether a schedule affected results?

Select a time step with a nonzero scheduled loss and compare the expected adjustment with the modeled result, accounting for other enabled losses.

What should be checked for PVWatts availability losses?

Check the Edit Losses settings and whether the separate Availability loss category is set in a way that could duplicate the same operating loss.

What if the enable state is not visible in the evidence?

The application of the schedule should be marked unknown; the table only supports that schedule values were retained.