How to model partial grant funding

Hi, I'm working on modeling a distributed generation project for a wastewater treatment plant. The solar project (somewhere in the neighborhood of 500 kW) is receiving 50% grant funding and 50% loan funding (3% interest, 20 year term). Is there a way to account for grant funding in the financial setup so that it doesn't look like the grant recipient has to pay it back, and so that it isn't included in the payback period calculation? Also, if the loan period for half of the project funding is 20 years, and cash-flow is positive annually, how come the payback period can be more than 20 years?
Thanks!

Hello,
There are a couple of ways to model a grant. You could use the Investment Based Incentive input on the Incentives page to enter it as a percentage of the total installed cost, or you could reduce the installation cost on the System Costs page by the amount of the grant.
One way to use a different payback calculation method than SAM's is to export the cash flow from SAM to excel by clicking Send to Excel with Equations on the Cash flow tab of the Results page. Then you can manually change the initial investment amount or make other adjustments in the payback cash flow to recalculate the payback period.
Without seeing your .sam file, it is hard for me to know what is causing the payback period to be higher than you expect. SAM calculates the payback period based on initial investment, electricity bill savings, and annual expenses, so adjusting one of those factors should change the payback period.
Best regards,

Paul.