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Solar Warehouse Calculator

Enter your warehouse size, monthly kWh, and demand charges — get system size, MACRS depreciation savings, demand charge reduction, payback, and 25-year NPV.

Warehouse details
sqft
kWh/mo
$/kWh
$/kW/mo
Commercial solar system for your warehouse
300 kW system — 750 × 400W panels
Roof coverage33% of roof
Electricity offset100%
Gross system cost$569,349
Federal ITC (30%)-$170,805
MACRS + 20% bonus depr. (tax savings)-$142,337
Net cost after incentives$256,207
Annual energy savings$42,000/yr
Annual demand charge reduction$4,009/yr
Total annual savings$46,009/yr
Simple payback5.6 yrs
25-year NPV (7% discount)$248,952
Estimated IRR17.6%
CO2 offset81 tons/yr
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Extended AnalysisRoof sizing, MACRS+ITC model & financing comparison
ft²
kWh
$/kWh
$/kW/mo
%
%
Your 50,000 ft² roof supports a 438 kW system using 35,000 ft² (100% of usable area). Usable area after fire code setbacks and HVAC units: 35,000 ft².
013,12526,25039,37552,50050,000 ft²Total roof35,000 ft²Usable area35,000 ft²Panels occupy
Fire Code Setback Requirements (IFC 2021)
Perimeter setback
6 ft from roof edge on all sides
Ridge setback
18 in from ridge line
Access pathways
4 ft wide pathway every 150 ft of roof
HVAC clearance
3 ft around all mechanical units

How to Use This Calculator

Enter warehouse size and roof type

Start with your warehouse square footage. The calculator assumes approximately 1 kW of solar per 90 sqft of roof — about 65% usable after accounting for HVAC units, skylights, setbacks, and racking spacing. A 50,000 sqft warehouse can typically support 500-600 kW of rooftop solar, sufficient to offset most single-shift operations.

Enter electricity usage and operating hours

Find monthly kWh consumption on your utility bill — not the dollar amount, the actual kilowatt-hours. Operating hours affect two things: how much solar is consumed on-site (better for daytime shifts) and how much demand charge reduction solar provides. Single-shift (8hr) warehouses see the most demand charge benefit because peak solar production overlaps with peak load.

Enter demand charges — often the biggest savings

Demand charges are billed on your peak 15-minute consumption each month and range from $8-25/kW for commercial customers. A 200 kW warehouse with $15/kW demand charges pays $3,000/month just in demand — solar can cut this 15-20% for daytime operations, adding $5,000-7,000/year in demand savings on top of energy savings.

The Formula

Adjusted Monthly kWh = Monthly kWh × 1.30 (if cold storage) Annual kWh = Adjusted kWh × 12 System kW = Annual kWh ÷ 365 ÷ PSH ÷ 0.80 efficiency Roof Capacity kW = Warehouse sqft ÷ 90 sqft/kW Actual System kW = min(Required kW, Roof Capacity kW) Gross Cost = Actual kW × 1000 × $1.90/W ITC = Gross Cost × 30% MACRS Bonus Depr (2026) = 20% bonus + regular 5yr on remaining 80% Tax Savings = Total Depreciation × 25% tax rate Net Cost = Gross Cost − ITC − Tax Savings Energy Savings = Annual kWh × Offset% × Rate Demand Savings = Peak kW × Reduction Factor × Demand Charge × 12 NPV = ∑(Annual Savings ÷ (1.07)^year) − Net Cost

The $1.90/W commercial installed cost benchmark reflects 2025 pricing for 100kW+ systems. Smaller systems (50-100 kW) may cost $2.10-2.40/W; larger systems (500kW+) can approach $1.60/W. The 20% bonus depreciation rate reflects 2026 tax law — this percentage has been stepping down from 100% (2022) and may change again after 2026.

Example

Mid-Atlantic Distribution Center — 100,000 sqft, double shift

A 100,000 sqft distribution center runs 12 hours/day, consumes 60,000 kWh/month, pays $0.10/kWh energy + $15/kW demand charges. They want to know their ROI on a rooftop solar installation.

Warehouse size100,000 sqft
Monthly kWh60,000 kWh/mo
Operating hours12 hrs/day
Utility rate$0.10/kWh + $15/kW demand

Result

System size~500 kW (1,250 panels)
Roof coverage~28%
Gross cost~$950,000
ITC (30%)-$285,000
MACRS tax savings-$178,000
Net cost~$487,000
Annual energy savings~$72,000/yr
Annual demand savings~$29,000/yr
Simple payback~4.8 yrs
25-yr NPV~$1.2M

After ITC and MACRS depreciation, the net cost drops from $950,000 to under $490,000. With $101,000/year in combined energy and demand savings, the system pays back in under 5 years and generates over $1.2M in NPV over 25 years. The demand charge savings alone ($29K/year) contribute nearly 30% of the total return.

FAQ

Commercial rooftop solar for warehouses typically costs $1.60-2.40/W installed in 2025, depending on system size and complexity. Systems 100-500 kW average around $1.90/W; smaller systems (50-100 kW) cost more per watt. Ground-mounted alternatives cost $1.20-1.60/W but require land. Compared to residential solar at $2.50-3.50/W, commercial solar benefits from lower per-panel costs, simpler installation (flat roofs), and economies of scale.
Solar equipment qualifies for MACRS 5-year depreciation, allowing businesses to depreciate the full system cost over 5 years for tax purposes. In 2026, a 20% first-year bonus depreciation applies: you immediately deduct 20% of cost, then depreciate the remaining 80% on the standard MACRS schedule. At a 25% corporate tax rate, this creates tax savings of roughly 18-22% of system cost in the first few years — significantly reducing the effective net cost. The bonus depreciation percentage has been declining from 100% (2022) → 60% (2024) → 40% (2025) → 20% (2026).
Yes — solar can reduce demand charges 10-25% for warehouses with daytime operations. The mechanism: your peak demand typically occurs during operating hours (lighting, HVAC, forklifts, loading docks). Solar production peaks at the same time. By generating on-site power at peak hours, you reduce the net demand the utility sees. The effect is strongest for single-shift operations (peak demand overlaps perfectly with solar noon). For 24/7 cold storage, peak demand often occurs at night, so solar has minimal demand charge impact unless paired with batteries.
Cold storage warehouses are excellent solar candidates due to high electricity consumption — typically 15-20 kWh/sqft/year versus 6-8 kWh/sqft/year for dry storage. Higher usage means larger systems, greater savings, and better economics. The challenge: refrigeration compressors often run 24/7, so a significant portion of load happens at night. Solar offsets roughly 30-40% of cold storage consumption without batteries. Adding battery storage can push solar utilization to 70-80% and significantly reduce peak demand charges from overnight compressor cycles.
Warehouse rooftop solar requires a structural engineering assessment before installation. Key factors: (1) Roof load capacity — solar adds 3-5 lbs/sqft, and most modern warehouses can handle this, but older structures may need reinforcement. (2) Roof age — if the roof needs replacement in 5-10 years, do it before installing solar to avoid expensive panel removal. (3) Membrane compatibility — TPO and EPDM membranes work well with ballasted systems; older built-up roofs may need adhesive mounts. (4) Drainage — panels must not block roof drains. Ballasted systems (weights instead of penetrations) are most common for flat warehouse roofs.

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