SAM - Latest Version of Software Upgrade

What is the technical reason why SAM is now using 1.3 DC/AC Ratio as default value?
Enrique Castro

Hi Enrique,

For the Detailed PV configurations, the DC/AC ratio is calculated based on the result of the choice module, inverter, and number of modules and inverters. We updated the module and inverter for the default configurations to use more up-to-date models.

For the default Detailed PV / Single Owner and other front-of-meter (FOM) financial model configurations, the DC/AC ratio is 1.33 in both SAM 2024.12.12. and SAM 2023.12.17. For the other configurations (Residential, Commercial, etc.) the default DC/AC ratio is less than 1.3.

For PVWatts configurations the DC/AC ratio is an input. For PVWatts / Single Owner and other FOM financial model configurations, the default DC/AC ratio is 1.3 in both SAM 2024.12.12 and SAM 2023.12.17. The default DC/AC ratio is less than 1.3 for other financial models.

In any case, the SAM's default values are intended as a starting point for your analysis. You should set the inputs as appropriate for your analysis needs.

Here is additional information about PV defaults from the SAM 2024.12.12 release notes:For Detailed PV and PVWatts configurations, update default system designs based on DOE Solar Photovoltaic System Cost Benchmarks :

• Behind-the-meter residential is 7.9 kWdc fixed roof-mount with 400 Wdc monofacial modules and 7.6 kWac string inverters with DC optimizers.
• Behind-the-meter commercial and third party ownership is 560 kWdc fixed or rack-mounted with 530 Wdc bifacial modules and 227 kWac central inverters. It is based on both the 3 MW agrivoltaic (APV) system from the DOE Solar Photovoltaic System Cost Benchmarks and the 200 kW fixed roof-mount system from the 2024 Annual Technology Baseline (ATB) .
• Front-of-meter is 100 MWdc ground-mounted, single-axis tracking with 530 Wdc bifacial modules and 2.5 MWac central inverters.
• PVWatts default system designs assume monofacial modules because bifacial option is hidden in collapsed "Advanced Parameters" panel. See SAM Issue 1959 .

Please let me know if there is a specic configuration that you have questions about.

Best regards,
Paul.