Live Demo — Energy Balance Calculator
Enter your panel power, seasonal sunshine hours and daily load to see whether the system runs a surplus or deficit.
Energy Balance Calculator
Free professional energy balance calculator for off-grid solar lighting systems. Compare charge-side generation (panel power × sunshine hours × charging efficiency) with discharge-side consumption in both summer and winter, then evaluate the battery capacity in Wh and the number of winter deficit days.
Key Features
Charge-Side Parameters
Input solar panel power (W), summer and winter sunshine hours and the total charging efficiency of the system.
Discharge-Side Parameters
Set daily power consumption and night-only consumption in Wh to define the load the system must feed.
Storage Parameters
Enter battery capacity in Ah and system voltage (12V / 24V / 48V) to calculate total stored energy in Wh.
Seasonal Balance
View daily generation, daily net energy and an automatic surplus or deficit status for both summer and winter.
Battery Status Analysis
See the total battery capacity in Wh and the estimated number of winter deficit days the system may face.
Clear Result Dashboard
All key figures are grouped in one result view so you can quickly judge whether the design self-balances.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | E_gen = P_pv × H × η_charge; E_balance = E_gen - P_daily |
| Solar Panel Power | 10 - 1000 W |
| Sunshine Hours | 2 - 8 h/day (summer & winter) |
| Charging Efficiency | 70% - 98% |
| Daily Power Consumption | 10 - 5000 Wh/day |
| Battery Capacity | 10 - 1000 Ah |
| System Voltage | 12V / 24V / 48V |
| Industry Standards | IEC 61724-1, AS/NZS 4509.2 |
| Output | Summer/winter generation & net energy, balance status, battery Wh, winter deficit days |
Frequently Asked Questions
How is the daily energy generation calculated?
Daily generation multiplies the solar panel power by the daily peak sun hours and the charging efficiency: E_gen = P_pv × H × η_charge. For example, a 150W panel with 5.0h of sun and 85% efficiency produces 150 × 5.0 × 0.85 = 638Wh/day.
What does the balance status tell me?
The daily net energy is generation minus consumption (E_balance = E_gen - P_daily). A positive value means an energy surplus, so the battery charges or stays full; a negative value means a deficit, so the system draws on stored battery energy and may not self-sustain.
Why check summer and winter separately?
Sunshine hours change strongly across the year. A system that balances in summer may run a deficit in winter. Checking both seasons reveals whether the panel and battery are sized for the least sunny period, which is the real constraint for off-grid lighting.
What is the winter deficit days result?
It estimates how many winter days the battery can cover a daily deficit before running empty, based on total battery capacity in Wh (capacity × voltage) divided by the winter shortfall. It is a quick reliability indicator: the more deficit days, the more the battery supports the load.
Thank you for choosing Open Solar Design