Example Data Table
| Project Type | Daily Use | Sun Hours | Panel Size | Losses | Approx Panels |
|---|---|---|---|---|---|
| Small cabin | 6 kWh | 5.5 | 400 W | 18% | 4 |
| Home backup | 18 kWh | 5 | 450 W | 20% | 11 |
| Large house | 35 kWh | 4.8 | 550 W | 22% | 18 |
Formula Used
Load with growth: Daily kWh × (1 + Growth ÷ 100)
Loss factor: (1 − System losses ÷ 100) × (Inverter efficiency ÷ 100)
Required array size: Load with growth ÷ (Peak sun hours × Loss factor)
Panel count: Required array watts ÷ Panel watt rating
Battery kWh: Daily kWh × Autonomy days ÷ (DOD × Battery efficiency)
Battery Ah: Battery kWh × 1000 ÷ Battery voltage
Controller amps: Array watts ÷ Battery voltage × Safety margin
Roof area: Number of panels × Panel length × Panel width
How to Use This Calculator
Enter your average daily energy use in kilowatt-hours. Add your local peak sun hours. Use a solar map or site survey for this value. Enter the watt rating of one panel. Add system losses for wiring, dust, heat, mismatch, and conversion.
Set battery values when storage is needed. Choose autonomy days for backup. Add battery voltage, depth of discharge, and battery efficiency. Enter peak load to size the inverter. Add roof area and panel dimensions to check space.
Press the calculate button. The result appears above the form. Download the data as CSV or PDF for records, proposals, or electrical planning.
Solar Panel Requirement Planning Guide
Why Solar Sizing Matters
Solar sizing starts with load. Every lamp, fan, pump, fridge, charger, and appliance adds demand. A small error can reduce backup time. A large error can raise cost. Good planning balances safety and budget. This calculator gives a practical estimate. It uses daily energy, sun hours, losses, and panel rating.
Daily Energy Is the Base
Daily energy use is the most important input. It is measured in kilowatt-hours. You can read it from a bill. You can also add appliance watts and running hours. Add future growth when new loads are expected. This keeps the system useful for longer.
Sun Hours and Losses
Peak sun hours are not the same as daylight hours. They show the useful solar energy available each day. A clear desert site may have high sun hours. A shaded roof may have lower output. Losses also matter. Heat, dust, wiring, inverter conversion, and tilt can reduce power. The loss percentage helps correct the array size.
Panel Count and Array Size
The calculator converts daily load into required solar array power. Then it divides array watts by single panel watts. The result is rounded upward. Rounding is important. You cannot install part of a solar panel. The actual array size may be slightly higher than the minimum need.
Battery and Inverter Planning
Battery sizing depends on backup days. It also depends on safe depth of discharge. Lithium batteries may allow deeper discharge. Lead acid batteries often need more spare capacity. Battery efficiency is included for a better estimate. Inverter size is based on peak load plus margin. This supports motor starts and short surges.
Roof Area Check
Space can limit a project. Panel length and width help estimate required roof area. The calculator compares this area with available roof space. Final design should also check shade, roof angle, wind load, wiring rules, and local electrical code.
FAQs
1. What is a solar panel requirement calculator?
It estimates panel count, array size, battery capacity, inverter size, controller rating, and roof area from your energy use and site conditions.
2. What are peak sun hours?
Peak sun hours represent usable solar energy for one day. They are different from total daylight hours and depend on location, season, weather, and shading.
3. Why are system losses included?
Real systems lose energy through heat, dust, wiring, inverter conversion, charge control, panel mismatch, and shading. Losses make the required array larger.
4. How do I find daily energy use?
Use your electricity bill, energy meter, or appliance list. Multiply each appliance wattage by daily use hours. Then divide total watt-hours by 1000.
5. Why is panel count rounded upward?
Solar panels are installed as whole units. Rounding upward ensures the system is not undersized after dividing the required array by panel wattage.
6. Does this calculator include batteries?
Yes. It estimates battery kWh and amp-hour capacity using daily load, autonomy days, battery voltage, depth of discharge, and battery efficiency.
7. Is roof area always enough for solar panels?
No. Roof area, shade, spacing, tilt, access paths, and local rules can reduce usable space. Always verify layout before buying equipment.
8. Can this replace a professional design?
No. It gives a planning estimate. Final solar designs should follow electrical codes, utility rules, structural limits, and equipment manufacturer instructions.