Calculator Inputs
Use this estimator to size a solar array, battery bank, controller, roof area, energy output, savings, and yearly carbon offset.
Plotly Graph
The chart compares estimated monthly solar generation against the adjusted monthly energy need.
Example Data Table
| Example Item | Value | Notes |
|---|---|---|
| Daily Load | 18.00 kWh/day | Typical moderate residential use. |
| Future Load Growth | 10.00% | Allows for later expansion. |
| Peak Sun Hours | 5.50 hours | Good solar resource location. |
| Panel Wattage | 550 W | High-output modern module. |
| Installed Array | 4.40 kW | Eight panels at 550 W each. |
| Estimated Annual Output | 7,122.93 kWh | Based on losses and inverter efficiency. |
| Battery Storage | 35.16 kWh | Supports backup autonomy. |
| Roof Area Needed | 17.60 m² | Assumes 2.2 m² per panel. |
Formula Used
Adjusted Daily Load = Daily Load × (1 + Future Load Growth ÷ 100)
Overall Efficiency = (1 - System Losses ÷ 100) × (Inverter Efficiency ÷ 100)
Required Solar Array (kW) = Adjusted Daily Load ÷ (Peak Sun Hours × Overall Efficiency)
Panels Needed = Ceiling[(Required Solar Array × 1000) ÷ Panel Wattage]
Installed Array (kW) = Panels Needed × Panel Wattage ÷ 1000
Battery Storage (kWh) = [(Adjusted Daily Load ÷ Inverter Efficiency) × Backup Days] ÷ Battery DoD
Battery Bank Capacity (Ah) = Battery Storage × 1000 ÷ Battery Voltage
Annual Output = Installed Array × Peak Sun Hours × Overall Efficiency × 365
Annual Savings = Annual Output × Electricity Rate
CO2 Offset = Annual Output × CO2 Factor
How to Use This Calculator
- Enter your present daily energy demand in kilowatt-hours.
- Add a future load growth percentage if you expect more appliances later.
- Fill in site peak sun hours using local solar data.
- Choose the panel wattage you plan to buy.
- Enter realistic system losses for dust, wiring, temperature, and mismatch.
- Set inverter efficiency, battery backup days, battery voltage, and battery depth of discharge.
- Add electricity cost, panel area, and CO2 factor for savings and emissions estimates.
- Press Estimate Solar System to show results above the form, export them, and view the monthly graph.
Frequently Asked Questions
1. What does peak sun hours mean?
Peak sun hours represent the equivalent number of full-intensity sunlight hours received in one day. It is not the same as total daylight time.
2. Why are system losses important?
Losses account for inverter conversion, wiring, temperature, dust, shading, and module mismatch. Ignoring them usually makes the system look smaller than it should be.
3. Why does the calculator include future load growth?
Future growth helps size the array for expanding demand, such as adding air conditioning, pumps, servers, or electric vehicles later.
4. How is battery storage estimated?
Battery storage is based on adjusted daily demand, required backup days, inverter efficiency, and allowable battery depth of discharge.
5. What is battery depth of discharge?
Depth of discharge is the usable share of total battery energy. Higher usable discharge lowers required battery size, but chemistry limits still matter.
6. Is the annual production exact?
No. It is a planning estimate. Real production changes with weather, tilt, orientation, shading, cleaning, equipment quality, and seasonal conditions.
7. How should I use the roof area result?
Use it as a quick spacing estimate. Real layouts also need walkways, tilt gaps, parapet clearance, and structural checks.
8. Can this calculator work for off-grid and hybrid systems?
Yes. It is useful for grid-tied, hybrid, and off-grid planning. Battery autonomy inputs become especially important for off-grid designs.