SAM (System Advisor Model)

Key Takeaways

• SAM = NREL’s open-source solar simulation + financial modeling tool.
• Free download; widely used for bankability cross-checks.
• Granular MPPT and per-step loss modeling.
• Full project finance: LCOE, IRR, NPV, tax equity.
• Scriptable via Python/MATLAB/JS SDK.

SAM Explained

SAM runs the same kind of hourly time-step simulation as commercial tools, but folds a full financial model into the same run rather than treating energy yield and project economics as separate steps. On the energy side, it uses site weather data — typically sourced from NSRDB / TMY3 for US sites or a Meteonorm dataset elsewhere — and models module and inverter behavior down to the MPPT algorithm level, which is one reason developers use it to sanity-check inverter clipping and tracking losses reported by other tools. On the finance side, the same hourly output feeds directly into LCOE, IRR, NPV, and tax-equity calculations, so a single SAM case file can answer both “how much energy will this produce” and “does the deal pencil out.”

Storage is modeled with configurable AC- or DC-coupled dispatch, which puts SAM in similar territory to purpose-built dispatch tools like HOMER Grid for grid-tied storage optimization and HOMER for off-grid and hybrid microgrid sizing — SAM trades some of their dispatch-optimization depth for tighter integration with US incentive structures (ITC, MACRS depreciation) and PPA-style financial outputs.

Worked Example: Cross-Checking a Bankable Yield Estimate

A common use case on a utility-scale project: the EPC’s PVsyst report produces the primary P50/P90 yield numbers for the lender, but the independent engineer or the developer’s own finance team re-runs the same system definition — same weather file, same module and inverter parameters — in SAM as a cross-check. If the two tools land within a few percent of each other, that agreement supports the PVsyst numbers going into the debt-sizing package; a larger gap sends the team back to compare loss assumptions (soiling, DC wiring, MPPT tracking efficiency) line by line before the report ships. Our guide on advanced PVsyst analysis walks through the loss-assumption side of that comparison in more detail.

Related Reading

SAM’s role tends to come up right after a PVsyst-based yield report is finished, when a lender or IE wants an independent second opinion using open-source, auditable methodology — our bankable PVsyst reports guide covers what that documentation package typically needs to include. For teams comparing the broader design-software landscape rather than just the finance-modeling layer, Best Solar Design Software in 2026: 10 Platforms Ranked places SAM alongside PVsyst, Helioscope, and Aurora by use case. Because SAM’s financial outputs (LCOE, IRR, NPV) map closely onto what a commercial developer needs when assembling a project proposal, the same modeling logic shows up on the delivery side in commercial solar proposal software, and on ground-mount utility-scale projects — where SAM’s bankability cross-checks matter most — in ground-mount solar park EPC work.