| Mode | Daily Energy (kWh/day) | Sun Hours (h/day) | Losses (%) | Panels (pcs) | Array Actual (kWdc) | Inverter (kWac) | Battery (kWh) | Area (m²) |
|---|---|---|---|---|---|---|---|---|
| HYBRID | 24.00 | 5.20 | 15.0 | 11 | 6.05 | 5.45 | 32.6 | 24.2 |
- Derate factor: derate = (1 − losses%) × inverter_eff%
- PV array sizing: array_kW = daily_kWh ÷ (peak_sun_hours × derate)
- Panel count: panels = ceil(array_kW × 1000 ÷ panel_W)
- Inverter recommendation: inverter_kW ≈ array_kW_actual × ratio
- Battery sizing (hybrid/off-grid): battery_kWh = (daily_kWh × autonomy_days) ÷ (DoD × battery_eff)
- Battery Ah: Ah = (battery_kWh × 1000) ÷ battery_V
- Charge controller current: I = (panels × panel_W ÷ battery_V) × safety
- Choose the design mode that matches your site power strategy.
- Enter daily energy use by summing equipment loads and hours.
- Set peak sun hours for your location and season planning.
- Adjust losses and inverter efficiency to match expected quality.
- Select your panel wattage and area for footprint estimation.
- For hybrid/off-grid, enter autonomy, DoD, efficiency, and voltage.
- Press Calculate to view results above the form.
- Use the CSV/PDF buttons to export the latest computed result.
Why accurate PV sizing matters on active sites
Construction power demand is rarely constant. Welders, compressors, pumps, lighting towers, site offices, and charging stations create peaks that influence inverter selection and energy storage needs. Oversizing increases capital cost and space requirements, while undersizing leads to generator fallback, downtime risk, and battery stress. This calculator converts daily energy targets and solar resource assumptions into a practical array size, panel count, and footprint that can be checked against available roof area.
Interpreting peak sun hours and derating
Peak sun hours represent the equivalent number of hours per day when solar irradiance averages 1 kW/m². Values vary by season, dust, and shading. System losses combine wiring voltage drop, module temperature effects, soiling, mismatch, and controller losses. Inverter efficiency converts array energy into usable AC energy. The derate factor aggregates these impacts so the recommended PV capacity matches your delivered energy target more reliably.
Selecting panels and estimating space
After the target array capacity is calculated, the panel count is rounded up to ensure the site meets energy needs even when output fluctuates. Panel area provides a first-order footprint for roof or ground mounting. For layout planning, keep additional clearance for access walkways, drainage paths, parapets, and wind ballast zones. If the roof check shows a mismatch, consider higher-wattage modules, reducing losses, or shifting noncritical loads to grid supply.
Battery and controller sizing for resilient power
Hybrid and off-grid systems depend on storage for autonomy during low-sun periods and overnight loads. Battery sizing uses autonomy days, allowable depth of discharge, and battery efficiency to estimate nominal storage. Converting kWh to amp-hours at the chosen battery voltage helps compare battery bank configurations. The charge controller current estimate includes a safety factor to cover operating margin and cold-weather increases in array output.
Example data for quick validation
Try this scenario to validate your inputs: Daily energy 24 kWh/day, peak sun hours 5.2, losses 15%, inverter efficiency 96%, panel wattage 550 W, panel area 2.2 m², inverter ratio 0.90, autonomy 1 day, DoD 80%, battery efficiency 92%, battery voltage 48 V, safety factor 1.25. The output should indicate a mid‑single‑digit kW array, a small group of panels, and a battery sized to cover roughly one day of demand.
1) What is the difference between grid-tied, hybrid, and off-grid modes?
Grid-tied focuses on array and inverter sizing for daytime production. Hybrid adds batteries for backup and shifting loads. Off-grid assumes solar and batteries supply all energy, so autonomy and storage assumptions become critical.
2) How should I estimate daily energy use on a construction project?
List each load, multiply rated power by run hours, then sum to kWh/day. Include site office HVAC, lighting, charging, and standby consumption. If loads vary, use a conservative high-demand day for sizing.
3) What losses value is reasonable for typical installations?
Many systems use 10–20% total losses depending on dust, heat, wiring length, and shading. If the site is dusty or panels run hot, choose a higher loss value to avoid under-sizing.
4) Why does the calculator use an inverter sizing ratio?
The ratio maps DC array size to AC inverter capacity. A slightly smaller inverter can be economical and still perform well, while a larger ratio may suit high peak loads. Use manufacturer limits and site load behavior.
5) How do autonomy days and DoD affect battery size?
More autonomy increases required storage linearly. Lower allowable DoD means you use less of the battery, so nominal capacity must increase. Both choices improve resilience but raise battery cost and footprint.
6) What does the roof fit check mean?
It compares estimated panel area against usable roof area. If it does not fit, you may need fewer loads, higher-efficiency modules, a ground-mount area, or a hybrid approach where the grid covers part of demand.
7) Can I use this result for final engineering design?
Use it for early sizing, budgeting, and feasibility. Final design should verify structural loading, wind uplift, electrical protection, cable routing, shading analysis, and local code requirements, then confirm equipment datasheets and interconnection rules.