Home›Financial & ROI›Commercial Solar Calculator

Commercial Rooftop Solar Calculator

Enter your bill, roof area, and building type — get system size, ITC with adders, MACRS depreciation value, and true payback after all incentives.

Building & usage
$
$/kW
sq ft
ITC adders (2026)
Commercial solar analysis
300.0 kW system — 34% electricity offset
⚠ Roof fits 750 panels — system sized to roof capacity
System size300.0 kW (750 panels)
Annual production473,040 kWh/yr
Electricity offset33.8%
Demand charge reduction est.90.0 kW → $23,760/yr
Gross system cost$660,000
ITC (40% with adders)-$264,000
MACRS 5-yr depreciation value-$100,139
Effective cost after incentives$295,862
Total annual savings$80,525/yr
25-year total savings$2,707,423
Simple payback period3.7 yrs
Approx. IRR (25-yr)9.3%
Link copied to clipboard
Extended AnalysisSizing, 25-yr NPV & financing comparison
sqft
kWh
$/kWh
$
%
%
Estimated system: 100 kW based on 10,000 sqft usable area. Annual production: 141,255 kWh covering 23.5% of your demand.
Estimated monthly solar production (kWh)
0.0k3.2k6.5k9.7k12.9kJanFebMarAprMayJunJulAugSepOctNovDec
Peak season (Apr-Sep)Off-peak season
System size
100 kW
Annual production
141,255 kWh
Energy savings/yr
$16,951
Demand charge savings/yr
$7,200

How to Use This Calculator

Enter your billing details

Start with your average monthly electricity bill. The calculator estimates kWh consumption using the US commercial average rate of $0.12/kWh. Also enter your demand charge rate — this is a separate $/kW line on commercial utility bills and often represents 20-40% of total costs. Solar reduces demand charges by lowering your peak consumption during billing periods.

Define your roof and building type

Enter usable roof area in square feet. The building type applies a realistic utilization factor: warehouses can use 90% of roof space, while offices are limited to 75% due to HVAC units, skylights, setbacks, and mechanical equipment. Each 400W commercial panel requires approximately 22 sq ft including spacing and walkways.

Select ITC adders that apply

The 2026 base ITC is 30%. Three bonus adders can stack up to 50% total: the Energy Community adder (+10%) applies if your facility is in a former fossil fuel area, the Domestic Content adder (+10%) requires 40%+ US-manufactured components, and the Low-Income adder (+10%) applies in qualifying census tracts. Check each adder that applies to maximize your incentive value.

Review the full financial picture

Results show system size, annual production, electricity offset, demand charge reduction, gross cost, ITC value, MACRS depreciation value, effective cost after all incentives, total 25-year savings, payback period, and IRR. MACRS uses the 5-year schedule with 20% bonus depreciation available in 2026, assuming a 21% corporate tax rate.

The Formula

Monthly kWh Estimate = Monthly Bill ÷ $0.12 (commercial avg rate) Annual kWh = Monthly kWh × 12 Daily kWh = Annual kWh ÷ 365 System kW = Daily kWh ÷ Peak Sun Hours ÷ 0.80 (efficiency) Panels = System kW × 1000 ÷ 400W (round up) Roof Capacity = Usable Roof Area × Utilization Factor ÷ 22 sq ft/panel ITC Rate = 30% base + applicable adders (max 50%) ITC Amount = Gross System Cost × ITC Rate MACRS Depreciable Base = Gross Cost × 0.85 (ITC half-year convention) MACRS Tax Value = Depreciable Base × 0.85 (5-yr factor) × 0.21 (tax rate) Effective Cost = Gross Cost - ITC - MACRS Tax Value Annual Savings = Annual kWh Production × $0.12 + Demand Charge Savings Payback = Effective Cost ÷ Annual Savings

MACRS 5-year depreciation allows commercial solar owners to recover 85-90% of the system cost over 5 years through tax deductions. The depreciable basis is reduced by 50% of the ITC claimed (per IRS rules), which is why we use 0.85 of the gross cost. In 2026, 20% bonus depreciation is available in year one, improving first-year cash flow significantly.

Example

Texas Distribution Center — 200kW System

A distribution company in Texas has a $14,000/month electricity bill with $22/kW demand charges. They have 22,000 sq ft of warehouse roof and use domestic-content qualified solar panels.

Monthly bill$14,000/mo
Roof area22,000 sq ft (warehouse)
StateTexas (5.4 PSH)
ITC addersDomestic Content (+10%)

Result

System size200 kW (500 panels)
Annual production~314,000 kWh/yr
Electricity offset~18.5%
Gross system cost$440,000
ITC (40% with DC adder)-$176,000
MACRS 5-yr tax value-$66,700
Effective cost~$197,300
Annual savings~$43,000/yr
Payback~4.6 years

Commercial solar with ITC + MACRS can cut the effective cost by more than half. This warehouse recoups its investment in under 5 years and generates over $1 million in savings over 25 years — while also reducing demand charges that compound with every new billing period.

FAQ

The base Investment Tax Credit (ITC) for commercial solar in 2026 remains at 30% under the Inflation Reduction Act. Three bonus adders can increase this to 50%: the Energy Community adder (+10%) for projects in former fossil fuel areas, the Domestic Content adder (+10%) for systems using 40%+ US-manufactured components, and the Low-Income Communities adder (+10% base, +20% for direct low-income benefit). These adders stack, but total ITC cannot exceed 50%. The credit directly reduces federal income tax liability dollar-for-dollar — unlike a deduction, which only reduces taxable income.
Commercial solar qualifies for MACRS 5-year accelerated depreciation, allowing businesses to deduct the system cost over 5 years rather than 39 years (standard commercial property). In 2026, 20% bonus depreciation is available in year one (stepped down from 100% in 2022). The depreciable basis is reduced by 50% of the ITC claimed — so a $440,000 system with a $132,000 ITC has a depreciable basis of $374,000 (440,000 - 66,000). Combined with ITC, businesses typically recover 50-60% of system cost in year one through tax benefits alone, making the economics dramatically better than the sticker price suggests.
Commercial Property Assessed Clean Energy (C-PACE) is a financing structure where the loan is attached to the property, not the borrower. Repayment is through a voluntary special assessment on the property tax bill. Key advantages: 100% financing (no money down), long terms (10-25 years), fixed rates, and the assessment transfers with the property sale. C-PACE is available in 38 states as of 2026. The developer typically retains the ITC under PPA or lease structures — under C-PACE with direct ownership, the business keeps both the ITC and MACRS depreciation, making it the most financially attractive structure for profitable businesses.
Yes, but with important limitations. Demand charges are based on your peak 15-minute interval during the billing period. Solar reduces demand charges only when the peak demand window coincides with peak solar production (typically 10am-2pm). If your peak demand is in the evening or on cloudy days, solar alone won't reduce demand charges. Battery storage combined with solar is far more effective for demand charge reduction — it can target peak shaving at any time of day. This calculator estimates a 25-30% demand reduction, which is realistic for buildings with daytime operations but conservative to be safe.
Commercial solar panels are warranted for 25 years at 80% output by most major manufacturers (Tier 1: First Solar, LONGi, JA Solar, Canadian Solar). Actual lifespan is typically 30-35 years. Inverters last 10-15 years and require one replacement over a 25-year system life. Racking and wiring last the full system life. The MACRS 5-year depreciation schedule does not reflect useful life — it's an incentive mechanism. A properly maintained commercial system installed today will still produce significant power in 2051, long after the initial investment is fully recovered.

Related Calculators

💰 Solar ROI Calculator
Calculate net present value and IRR for residential and commercial solar.
✅ Solar Tax Credit Calculator
Calculate your federal ITC and state incentive for any solar project.
🔋 Battery Bank Calculator
Size a battery system for demand charge reduction or backup power.
📈 Solar Savings Calculator
Estimate long-term savings with utility rate escalation factors.

Embed This Calculator

Free to embed on your website. Just copy this code:

<iframe src="https://solarsizecalculator.com/commercial-solar-calculator"
  width="100%" height="700" frameborder="0"
  title="Commercial Solar Calculator"></iframe>