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A commercial solar system makes about 4 kWh per day for every kW at 5 peak sun hours, roughly the US average. So a 100 kW system makes about 400 kWh a day (12,160 a month), a 500 kW system about 2,000 kWh a day and a 1 MW plant about 4,000 kWh a day, or 1.46 million kWh a year.
This guide gives the output, panels, inverters, space and CO₂ savings for every common business size. It shows how output changes between the US, UK, Canada, Australia and Germany, what those kWh run in a factory, office, hospital or farm, and how to estimate payback with your own prices.
Business and industry solar calculator
Estimates use the formulas explained in this guide. Plan a complete system with the all-in-one calculator →
Output by system size
kWh per day = System size (kW) × Peak sun hours × 0.80
| System | 4 sun hours | 5 sun hours | 6 sun hours | Per month (5 h) | Per year (5 h) |
|---|---|---|---|---|---|
| 10 kW | 32 | 40 | 48 | 1,216 | 14,600 |
| 20 kW | 64 | 80 | 96 | 2,432 | 29,200 |
| 30 kW | 96 | 120 | 144 | 3,648 | 43,800 |
| 50 kW | 160 | 200 | 240 | 6,080 | 73,000 |
| 100 kW | 320 | 400 | 480 | 12,160 | 146,000 |
| 250 kW | 800 | 1,000 | 1,200 | 30,400 | 365,000 |
| 500 kW | 1,600 | 2,000 | 2,400 | 60,800 | 730,000 |
| 1 MW | 3,200 | 4,000 | 4,800 | 121,600 | 1,460,000 |
A 100 kW system in five countries
| Country | Peak sun hours | kWh per day | kWh per month | kWh per year |
|---|---|---|---|---|
| Australia | 6.0 | 480 | 14,592 | 175,200 |
| United States | 5.0 | 400 | 12,160 | 146,000 |
| Canada | 3.8 | 304 | 9,242 | 110,960 |
| Germany | 3.3 | 264 | 8,026 | 96,360 |
| United Kingdom | 2.9 | 232 | 7,053 | 84,680 |
Cities vary within each country. Phoenix (6.6) and Perth (5.8) are well above their national averages; Manchester (2.6) and Berlin (3.0) are below. Check yours in solar potential by country and peak sun hours.
Panels, inverters and space
Commercial systems use large 550 to 600 W modules. The figures below assume 580 W panels of about 2.58 m² each.
| System | Panels (580 W) | Inverters (typical) | Sloped / metal roof | Flat roof or ground | CO₂ avoided per year |
|---|---|---|---|---|---|
| 10 kW | 18 | 1 × 10 kW | 51 m² | 84 m² | 7 t |
| 20 kW | 35 | 1 × 20 kW | 99 m² | 163 m² | 14 t |
| 30 kW | 52 | 2 × 25 kW | 148 m² | 241 m² | 21 t |
| 50 kW | 87 | 2 × 25 kW | 247 m² | 404 m² | 35 t |
| 100 kW | 173 | 2 × 50 kW | 491 m² | 803 m² | 70 t |
| 250 kW | 432 | 3 × 100 kW | 1,226 m² | 2,006 m² | 175 t |
| 500 kW | 863 | 5 × 100 kW | 2,449 m² | 4,008 m² | 350 t |
| 1 MW | 1,725 | 4 × 250 kW | 4,896 m² | 8,011 m² | 701 t |
- Inverters are usually sized at about 85% of the panel kW (a DC/AC ratio of around 1.15), because panels rarely reach their rating. Above about 20 kW they are three-phase.
- Flat roofs and ground need more space than sloped roofs because tilted rows must be spaced so they do not shade each other. In the UK, Germany and Canada the sun is lower, so rows need wider gaps.
- Square feet: multiply m² by 10.76. A 100 kW system needs about 5,280 sq ft of sloped roof.
- A ground-mounted 1 MW plant with access roads, fencing and inverter rooms typically needs 1.5 to 2 hectares (about 4 to 5 acres).
- CO₂ uses a world-average grid of about 0.48 kg per kWh at 5 sun hours. Coal-heavy grids save more; hydro-rich grids save less.
What each size runs
The calculator builds a realistic equipment mix for each type of business. At 5 sun hours:
- 20 kW office: five 18,000 BTU office mini-splits (1.6 kW each) for 8 hours, 8 computers, 23 LED panels, a lift, printers, a break room, a water dispenser and CCTV.
- 50 kW hospital: three 2-ton rooftop HVAC or mini-split systems (2.4 kW each) for 16 hours, 39 lights, 3 oxygen concentrators, lab equipment, an autoclave, 4 medicine fridges, 11 computers, a water pump and X-ray.
- 100 kW factory: three 10 HP machine motors for 8 hours, a 15 kW air compressor, 44 LED high-bays, 5 exhaust fans, 3 office HVAC systems (2-ton, 2.4 kW), a welding machine and office equipment.
- 100 kW warehouse: 91 LED high-bays for 12 hours, 4 forklift chargers, 10 dock doors and conveyors, 4 office HVAC systems and 20 computers.
- 1 MW factory: about 35 machine motors of 10 HP, 10 air compressors, 315 high-bay lights, 42 exhaust fans and 30 office HVAC systems on a working day.
Large single machines are the exception. A 37 kW (50 HP) mill motor uses about 296 kWh in a 10-hour shift. A 100 kW system covers about 8 hours of it at 5 sun hours, plus the conveyors and lighting.
Self-use, surplus and why working days matter
A business only saves the full price of a kWh when it uses that kWh itself. Solar made on Sundays, holidays or during a slow afternoon is exported to the grid (if allowed), stored in batteries, or lost.
The calculator works this out from your bill, your working days and the share of your use that happens in daylight. Two sizes come out of it:
- Size to cover daytime use: almost every kWh is used on site. This gives the fastest payback where export prices are low, which is the case in most of the UK, Germany and Australia.
- Size to offset the whole bill: this needs net metering or a good export price. Net metering rules differ by US state and by Canadian province.
Estimating payback
Payback (years) = System cost ÷ yearly savings
Yearly savings = (kWh used on site × your price) + (kWh exported × export price)
Example with assumed US prices: a 100 kW system at 5 peak sun hours makes 146,000 kWh a year, and 80% (116,800 kWh) is used on site. At an assumed $0.15 per kWh that saves $17,520 a year. The other 29,200 kWh are exported at an assumed $0.05, adding $1,460. Total savings are $18,980 a year. If the system costs an assumed $1.50 per watt ($150,000), payback is 150,000 ÷ 18,980 = 7.9 years. If the business qualifies for an assumed 30% tax credit, the net cost falls to $105,000 and payback to 5.5 years.
These prices are for illustration only. The same system makes less in the UK or Germany, but businesses there often pay more per kWh, which offsets part of the difference. Enter your own prices and sun hours in the calculator.
Incentives by country
Rules change often. Treat these as starting points and confirm them before you sign.
- United States: the 30% residential credit (Section 25D) ended for systems installed after December 31, 2025. Businesses can still claim the Section 48E investment credit for a limited time: a base rate of 6%, or up to 30% when prevailing wage and apprenticeship rules are met. Check current eligibility deadlines with a tax adviser. See solar panels in the USA.
- United Kingdom: solar bought by a business can qualify for capital allowances such as full expensing or the Annual Investment Allowance. Check with an accountant. Exported power can earn Smart Export Guarantee (SEG) payments. See solar panels in the UK.
- Australia: systems up to 100 kW can create small-scale technology certificates (STCs), which lower the upfront price. See solar panels in Australia.
- Germany: larger systems can receive EEG feed-in payments for exported power, but self-consumption is what makes most business systems pay. See solar panels in Germany.
- Canada: provincial programs and net metering rules vary. Check with your province and utility. See solar panels in Canada.
Things to check before you buy
- Roof strength and condition. Panels and mounting add about 12 to 15 kg per m² (2.5 to 3 lb per sq ft). Old roofs should be replaced first. In Canada and northern Germany, check snow loads too.
- Grid connection approval. Many utilities cap export or require a special meter. In the UK, larger systems need approval from the distribution network operator. In Germany every system must be registered in the Marktstammdatenregister. Where export is not allowed, fit a zero-export controller.
- Generator integration. Sites with frequent outages need inverters that can work alongside a backup generator without back-feeding it.
- Motor starting. Use soft starters or variable-frequency drives (VFDs) on large motors so start-up surges do not trip the inverters.
- Cleaning and access. Industrial dust can cut output by 20% or more. Plan walkways and a water point for cleaning.
FAQ
How many kWh does a 100 kW solar system produce per day?
About 400 kWh at 5 peak sun hours, the US average. Expect about 480 kWh in Australia, 304 in Canada, 264 in Germany and 232 in the UK on an average day.
How much land is needed for a 1 MW solar plant?
About 1.5 to 2 hectares (roughly 4 to 5 acres) for a ground-mounted plant, including spacing between rows, roads and equipment areas.
How many panels are in a 100 kW system?
About 173 panels of 580 W, or 182 panels of 550 W.
Can a commercial system work without the grid?
Only with batteries or a generator. A standard on-grid commercial system shuts down when the grid fails.
Related guides
- Uses of Solar Energy: 30 Ways Homes, Businesses, Farms and Cities Use Solar Power
- Solar for Shops, Restaurants and Hotels: Size, What It Runs and Savings
- Solar for Schools and Hospitals: Size, What It Runs and Backup
- Solar for Poultry and Dairy Farms: Fans, Chillers, Pumps and Backup
Sources and further reading
- IRS: Instructions for Form 3468: business investment credits for energy property.
- DSIRE: Database of State Incentives for Renewables & Efficiency: solar rebates and net metering rules by US state.
- NREL PVWatts Calculator: solar output estimate for any address.