Hi Nathan,
The net present value shown on the metrics page is based on the project after-tax cash flow, and as such accounts for both project costs and benefits. It includes not only capital, maintenance, and replacement costs, but also electricity bill savings, debt, taxes, and incentives. The NPV is positive when benefits over the project life are greater than the initial investment, and negative when the reverse is true.
The present values calculated by the Battery Financials macro are of annual costs only: capital, maintenance, replacement, and electricity bill costs. Those present values are always positive. They are meant to give an indication of the relative cost of providing electricity to the building with no system, a PV-only system, and a PV system with battery, ignoring electricity bill savings, incentives, and other benefits.
Best regards,
Paul.