Commercial Solar Energy Savings Calculator
Use the estimator below if unsure of system size
Includes 30% base + 10% domestic content adder
Results show gross cost vs net cost after ITC and depreciation -- the before/after that changes the investment decision.
Your Commercial Solar Savings Estimate
Not sure what size solar system your facility needs? Use the estimator below to calculate the recommended system size in kilowatts based on your monthly electricity usage and how much of your bill you want solar to offset. Then bring that number into the savings calculator above.
Found on your monthly electricity bill
System Size Estimate
Enter this system size into the savings calculator above to estimate your net cost, payback, and 25-year ROI after federal incentives.
Get a Professional Solar AssessmentWhy the Gross Cost of Commercial Solar Is Misleading
Most businesses evaluate commercial solar the wrong way -- they look at the installed cost, run a simple payback calculation, and conclude the timeline is too long. That analysis is incomplete because it ignores the incentive stack that dramatically changes the real economics of the investment.
Unlike most capital equipment, commercial solar is heavily subsidized through federal tax credits, accelerated depreciation, and state-level incentives. Two identical $1,000,000 systems can have net costs as different as $225,000 and $600,000 depending on the business's tax position, location, and project structure. The gross cost tells you almost nothing about the real return. For a full breakdown of how these incentives stack, see The Real Economics of Commercial Solar.
The Commercial Solar Incentive Stack
Understanding the three layers of federal incentives is essential before evaluating any commercial solar proposal. The Investment Tax Credit is the primary driver, but MACRS depreciation adds a significant secondary benefit that most simple solar calculators ignore entirely.
| Incentive | Value | How It Works | Notes |
|---|---|---|---|
| Federal ITC -- Base | 30% | Direct dollar-for-dollar federal tax credit | Available to all eligible commercial systems |
| ITC -- Domestic Content Adder | +10% | Additional credit for FEOC-compliant domestic content | Requires eligible US-manufactured components |
| ITC -- Energy Community Bonus | +10% | Additional credit for qualifying Energy Community locations | Check eligibility at Treasury.gov |
| MACRS Bonus Depreciation | Tax Rate x ~87% | Accelerated 5-year depreciation with bonus depreciation in year one | Net basis is 85% of gross cost (ITC reduces depreciable basis by half) |
| State Incentives | Varies | State tax credits, REC payments, utility rebates | Check your state at DSIREUSA.org |
Worked Example: 500kW Commercial Solar System
Using the same inputs the FSG savings calculator applies -- a 500kW system at $2.00/watt with the 40% ITC (30% base + 10% domestic content) and MACRS depreciation at the 21% federal corporate tax rate.
Inputs
- System Size: 500 kW
- Installed Cost: $2.00/watt
- Gross System Cost: $1,000,000
- ITC Rate: 40% (30% base + 10% domestic content)
- Federal Tax Rate: 21%
- MACRS Bonus Depreciation: Yes
- Monthly Electric Bill: $10,000 / Solar Offset: 80%
Incentive Calculation
- Federal ITC (40%): -$400,000
- MACRS Depreciable Basis: $1,000,000 - ($400,000 / 2) = $800,000
- MACRS Depreciation Benefit: $800,000 x 21% = -$168,000
- Total Incentives: $568,000
- Net Cost After Incentives: $432,000
Savings Calculation
- Annual Energy Savings: $10,000 x 12 x 80% = $96,000/yr
- Gross Payback (no incentives): $1,000,000 / $96,000 = 10.4 years
- Net Payback (after incentives): $432,000 / $96,000 = 4.5 years
- 25-Year Savings (3% escalation): ~$3,400,000
- 25-Year ROI on Net Cost: ~687%
How to Size a Commercial Solar System
The size of a commercial solar system is determined by three factors: your monthly electricity consumption in kilowatt-hours, the percentage of that consumption you want solar to cover, and the peak sun hours available at your location. The basic formula is straightforward -- but the system size estimator above handles the calculation automatically.
Most commercial solar systems are sized to offset 75 to 90 percent of a facility's electricity usage rather than 100 percent. A full offset often requires more roof or ground space than is practical, and maintaining some grid connection provides reliability and simplifies net metering arrangements. The U.S. Department of Energy's commercial solar resources provide additional guidance on sizing, interconnection, and incentive eligibility for commercial and industrial facilities.
| Region | Peak Sun Hours | States | Impact on System Size |
|---|---|---|---|
| Southwest | 6.0 hrs | AZ, NV, NM, CA desert | Smallest system needed for a given output |
| South / Mountain West | 5.5 hrs | TX, CO, UT, KS | Excellent solar resource, strong ROI |
| Southeast | 5.0 hrs | FL, GA, SC, TN, AL | Good solar resource year-round |
| Midwest / Mid-Atlantic | 4.5 hrs | IL, OH, VA, NC, MO | Moderate resource, still strong economics |
| Northeast | 4.0 hrs | NY, PA, MA, CT, WI | Larger system needed, but economics work |
| Pacific Northwest | 3.5 hrs | WA, OR | Lowest resource -- system size increases accordingly |
Frequently Asked Questions
Ready for a real commercial solar proposal?
FSG designs and installs commercial solar systems for businesses, industrial facilities, and multi-site national accounts across the country. Get a project-specific assessment that accounts for your tax position, roof conditions, utility structure, and full incentive stack.