Panels for Business Calculator

Calculator Inputs

Enter your business energy and design assumptions. Submit to see results above this form.

Monthly energy use (kWh)

Use your recent average utility consumption.

Target offset (%)

Percent of load you want solar to cover.

Peak sun hours (daily)

Typical: 3–7 depending on location.

System losses (%)

Includes heat, wiring, inverter, soiling, mismatch.

Panel rating (W)

Example: 400–600 W per panel.

Panel area (m²)

Typical: ~1.8–2.4 m² per panel.

Electricity rate (currency/kWh)

Use blended energy rate if possible.

Installed cost (currency/W)

All-in installed cost per DC watt.

Incentives or rebates (currency)

Upfront grants, rebates, or credits value.

Annual O&M (% of capex)

Maintenance, cleaning, monitoring, insurance.

Panel degradation (%/year)

Typical: 0.3–0.8% per year.

Rate escalation (%/year)

Expected change in energy prices yearly.

Project life (years)

Common modeling: 20–30 years.

Grid emissions (kg CO₂/kWh)

Use local grid factor if known.

Reset

Example Data Table

Sample inputs and a typical output snapshot for quick reference.

Scenario	Monthly kWh	Offset %	Sun hours	Losses %	Panel W	Result (approx.)
Small office	2,500	80	5.0	14	500	~33 panels, ~16.5 kW
Retail store	4,500	85	5.0	14	550	~57 panels, ~31.4 kW
Light industrial	10,000	90	4.5	16	600	~161 panels, ~96.6 kW

Formula Used

1) Annual target energy

Annual target (kWh) = Monthly kWh × 12 × (Offset% ÷ 100)

2) Performance ratio (PR)

PR = 1 − (Losses% ÷ 100)

3) Required system size

Required kW (DC) = (Annual target ÷ 365) ÷ (Sun hours × PR)

4) Panels needed

Panels = ceil((Required kW × 1000) ÷ Panel wattage)

5) Expected production

Annual production (kWh) ≈ kW × Sun hours × 365 × PR

How to Use This Calculator

Find your average monthly kWh from recent bills.
Select how much of that load you want covered.
Enter local peak sun hours or a conservative estimate.
Set losses to reflect shading, heat, and equipment.
Choose a panel wattage and panel area from your vendor.
Enter your electricity rate and installed cost per watt.
Add incentives, then submit to view results above.
Download CSV or PDF for proposals and internal review.

Load Profiling for Commercial Sites

Commercial sizing starts with verified monthly kilowatt-hours from utility bills and interval meters. A stable baseline reveals constant loads like refrigeration, IT, and lighting. Seasonal peaks from cooling or production runs should be averaged across at least twelve months. This calculator converts monthly use into an annual target, then applies the selected offset percentage so proposals match budget and risk tolerance. It supports rapid scenario sensitivity checks.

Sun Hours, Losses, and Performance Ratio

Peak sun hours represent daily solar energy at your location and are the strongest driver of required array size. Real output is reduced by temperature, wiring, inverter conversion, soiling, shading, and downtime. Those effects are expressed as a performance ratio, calculated here as one minus total losses. For conservative planning, many businesses assume 0.75 to 0.85 depending on roof conditions and maintenance.

Panel Count and Roof Space Planning

Once required system capacity is estimated, panel count is computed by dividing total watts by the selected panel wattage. Using higher wattage panels reduces the number of modules, labor, and racking lines. Space feasibility is checked by multiplying panel count by panel area, then adding walkways and setbacks. If space is tight, consider carports, higher efficiency modules, or splitting the system across multiple structures.

Energy Value, Savings, and ROI Signals

Annual savings are estimated by multiplying produced kilowatt-hours by the electricity rate. Businesses on demand tariffs should treat this as an energy-only baseline; demand charge reductions depend on load timing and storage. Installed cost per watt is used to estimate project cost, then incentives are subtracted to form the net investment. The tool reports simple payback and a first-year return indicator for quick comparison across sites.

Using Results in Proposals and Operations

For proposal packages, export CSV to document assumptions, computed capacity, and financial outputs in a shareable format. Export PDF to capture results panels as a one-page summary for management approval. Operational teams can use the panel count and area estimates to plan maintenance access, cleaning schedules, and safety signage. Re-run scenarios by adjusting sun hours, losses, and incentives to stress-test outcomes before procurement.

FAQs

1) What does the offset percentage mean?

Offset is the share of your annual electricity use you want the system to cover. Choosing 60–90% often balances roof limits and budget, while 100% targets maximum coverage when net metering or onsite load is strong.

2) How do I pick peak sun hours?

Use a reliable local solar resource estimate for average daily peak sun hours. If you only have a range, choose the lower value for conservative sizing and update it after a site assessment.

3) Why include losses and performance ratio?

Losses capture real-world reductions from heat, wiring, inverter conversion, soiling, shading, and downtime. The calculator converts losses into a performance ratio so estimated production better matches typical commercial operating conditions.

4) Should I use higher wattage panels?

Higher wattage panels reduce module count and can simplify racking and wiring. They may cost more per panel, so compare cost per watt, efficiency, and availability with your installer or supplier.

5) How accurate is the roof area estimate?

It is a planning estimate based on module area only. Allow extra space for walkways, fire setbacks, tilt, obstructions, and maintenance access. A professional layout is needed before final procurement.

6) Is payback the same as project profitability?

No. Simple payback compares net cost to annual energy savings and ignores financing, demand charges, degradation, and future tariff changes. Use it for quick screening, then run a full financial model for approval.