How to calculate payback period for a commercial solar investment

Steps to estimate payback period

Calculating payback involves comparing the upfront cost (net of incentives) to annual cash savings from reduced electricity bills. The simple payback period is the number of years it takes for cumulative savings to equal the initial investment. For more accuracy, consider inflation, utility rate escalation, maintenance costs, and financing expenses.

Basic calculation steps:

• Determine total installed cost (equipment, installation, permits)
• Subtract expected incentives and tax credits to get net cost
• Estimate annual energy production and the dollar value saved based on current utility rates
• Calculate simple payback: Net cost ÷ Annual cash savings

Example and refinements

• Example: $200,000 net cost and $30,000 annual savings → 6.7 years simple payback
• For financed projects, include loan payments instead of just annual savings
• Consider levelized cost of energy (LCOE) and discounted cash flow (NPV, IRR) for a comprehensive view

A thorough financial model accounts for performance degradation, operation and maintenance costs, incentive expiration, and utility rate changes. Many solar providers supply modeled projections that help businesses understand realistic payback and long-term returns.