Solar Energy Needs Calculator

Enter daily power and sunlight values accurately. Compare panels, storage, inverter size, and production easily. Download clean reports for solar planning and budget review.

Calculator

Use kWh per day. Leave blank if using monthly use.
Use bill kWh per month.
Use 100 for full offset.
Includes heat, dust, wiring, and conversion loss.
Use square meters per panel.
Use square meters.
Use your money value per kWh.

Optional Appliance Load Rows

Appliance Watts Hours Per Day Quantity

Example Data Table

Use Case Daily kWh Sun Hours Panel Watts Loss Approx Panels
Small Cabin 6 5.5 400 20% 4
Family Home 24 5 450 22% 14
Workshop 12 4.5 400 25% 9

Formula Used

Daily energy: Daily kWh plus appliance kWh, or monthly kWh divided by 30.44.

Target solar energy: Daily energy × solar offset percentage.

System efficiency: 1 − system loss percentage.

Required array size: Target daily kWh ÷ peak sun hours ÷ system efficiency.

Panel count: Required array kW × 1000 ÷ panel watts. The result is rounded up.

Battery bank: Target daily kWh × autonomy days ÷ depth of discharge ÷ inverter efficiency.

Battery amp hours: Battery bank kWh × 1000 ÷ battery voltage.

Inverter size: Largest running load × surge factor.

How To Use This Calculator

Enter your known daily energy use if available. If you only know monthly use, enter the monthly kWh value instead. Add appliance rows when you want to include separate loads. Enter local peak sun hours, panel wattage, loss percentage, roof area, and battery settings. Press calculate. The result appears above the form and below the header. Use CSV for spreadsheet work. Use PDF for a simple report.

Solar Planning Made Practical

Solar sizing starts with daily energy demand. A home may use power from lights, pumps, fans, chargers, tools, and kitchen appliances. Each load adds to the daily total. The calculator lets you enter a known daily value, a monthly bill value, or separate appliance rows. Seasonal changes should be tested before choosing final equipment. Budget goals can guide offset too.

Peak sun hours are important. They describe useful sunlight for panel production. A site with five peak sun hours usually needs fewer panels than a site with three. Shade, dust, cable loss, heat, and inverter loss reduce output. That is why a loss field is included.

Panels And Battery Storage

Panel count is based on the target daily energy and the usable sunlight. The calculator divides the target load by peak sun hours and system efficiency. Then it compares that size with the selected panel wattage. The final number is rounded upward. This avoids an undersized array.

Battery size depends on autonomy days. One autonomy day means the battery should support the target load for one day. Depth of discharge protects battery life. A lower discharge setting requires a larger bank. Inverter efficiency also matters because stored energy is not delivered perfectly.

Inverter And Roof Checks

The inverter must handle the largest expected running load. Some motors need extra startup power. The surge factor helps include that short demand. A pump or compressor may need a much larger surge allowance than lighting.

Roof area gives a quick space check. The calculator compares the panel count with available mounting space. It uses panel area to estimate the maximum number of panels. This is only a planning check. Real layouts need setbacks, walkways, tilt, shade paths, and local electrical rules.

Use The Result Wisely

The result is a planning estimate, not a final design. It helps compare panel wattage, sun hours, losses, battery voltage, and backup days. You can download a CSV for spreadsheets. You can also save a PDF summary for discussion.

A licensed installer should verify wiring, protection, grounding, permits, roof strength, and grid rules. Still, a clear first estimate saves time. It turns a confusing solar idea into numbers you can review, share, and improve.

FAQs

What is a solar energy needs calculator?

It estimates panel count, array size, battery storage, inverter size, and expected energy output from your power use and sunlight data.

Should I enter daily or monthly kWh?

Use daily kWh when you know it. Use monthly kWh when you only have a utility bill. The calculator converts monthly use into daily use.

What are peak sun hours?

Peak sun hours measure useful solar energy during a day. Higher values usually reduce the number of panels needed for the same load.

Why is system loss included?

Solar systems lose energy through heat, dust, wiring, shading, charge control, and inverter conversion. The loss field creates a more realistic estimate.

How is battery size calculated?

Battery size uses target daily energy, backup days, depth of discharge, and inverter efficiency. More backup days require a larger battery bank.

Does the roof area result replace a site survey?

No. It is only a quick space check. Real designs need shade review, setbacks, mounting rules, roof strength checks, and local code review.

What inverter size should I choose?

The inverter estimate uses your largest running load and surge factor. Motor loads may need a higher surge allowance than lighting or electronics.

Can I download the calculation?

Yes. Use the CSV button for spreadsheet records. Use the PDF button for a simple report that summarizes the main results.

Related Calculators

Paver Sand Bedding Calculator (depth-based)Paver Edge Restraint Length & Cost CalculatorPaver Sealer Quantity & Cost CalculatorExcavation Hauling Loads Calculator (truck loads)Soil Disposal Fee CalculatorSite Leveling Cost CalculatorCompaction Passes Time & Cost CalculatorPlate Compactor Rental Cost CalculatorGravel Volume Calculator (yards/tons)Gravel Weight Calculator (by material type)

Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.