How many solar panels do I need for my home?

The number of panels depends on your daily energy consumption (kWh), your location's peak sun hours, panel wattage, and system losses. Our calculator uses real climate data to give you an accurate panel count.

What size battery do I need for solar?

Battery size depends on daily energy use, days of autonomy needed, depth of discharge (90% for lithium, 50% for lead-acid), and inverter efficiency. Enter your appliances and our calculator computes the exact Ah and kWh needed.

Should I use MPPT or PWM charge controller?

MPPT controllers are recommended for systems over 800W or with 48V battery banks. They harvest 20-30% more energy than PWM. Our calculator automatically recommends the right type and amperage rating based on your system size.

How accurate is this solar calculator?

This calculator uses 12 months of real historical solar radiation and temperature data from the Open-Meteo Archive API, applies multiplicative loss modeling, duty-cycle-corrected appliance loads, per-month temperature derating, and panel degradation factors for near-professional accuracy.

Solar System Calculator — Free Professional Panel, Battery & Inverter Sizing Tool

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Where are you located?

We fetch real sunshine & temperature data for your area

Your City or Town Works for virtually any city, town or village worldwide — millions of locations in every country. Uses 12 months of real recorded climate data.

Please enter a city name

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What will you power?

Tap appliances to add, then adjust quantity & hours with +/- buttons

Filter by Category

＋ Add a custom appliance

Name

Watts

Hours/day

Quantity

Please add at least one appliance

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System Preferences

Smart defaults are pre-set — adjust if you know better

Battery Chemistry Lithium costs more but lasts 3× longer

🔋Lithium90% usable · 10+ yr life

🪫Lead-Acid50% usable · 3-5 yr life

Days of Backup (Autonomy) How many days without sun can your batteries last?

1 day5 days

2 day(s)

Panel Size

System Voltage

Inverter Efficiency

Surge Factor

⚡ Advanced: Loss Factors & Expansion

Wiring Loss

Dust/Soiling

Shading

Expansion Buffer Add extra capacity for future growth

0%50%

20%

System Lifespan (for degradation)

Electricity Cost For savings estimate

/kWh

Currency Label for reports

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Your Solar System

Monthly Production vs. Consumption

Monthly Temperature & Panel Derating

☀️ Was this calculator helpful?

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How This Solar Calculator Works

This free solar system sizing calculator helps homeowners, installers, and off-grid enthusiasts determine exactly how many solar panels, what battery capacity, inverter size, and charge controller type they need. Unlike basic calculators that use generic estimates, this tool fetches 12 months of real historical solar radiation and temperature data from the Open-Meteo Archive API for your exact coordinates.

Accurate Solar Panel Sizing

Panel count is calculated using your actual daily energy consumption, real peak sun hours (PSH) derived from shortwave radiation data, temperature derating coefficients, multiplicative system losses (wiring, dust, shading), inverter efficiency, battery round-trip losses, and panel degradation over the system lifespan. This gives results within 5-10% of professional site assessments.

Battery Sizing: Lithium vs Lead-Acid

Battery capacity is sized based on depth of discharge (DoD) physics: 90% for lithium-ion and 50% for lead-acid. The calculator accounts for days of autonomy, inverter efficiency losses, and your expansion buffer to ensure your battery bank covers cloudy periods without damage to battery lifespan.

Charge Controller: MPPT vs PWM

The calculator automatically recommends MPPT or PWM controllers based on your system size and voltage. It computes string configuration (series × parallel), required amperage with safety margins, and accounts for the specific Vmp and Imp values of your chosen panel wattage (300W through 750W).

Data Source & API Limits

Solar radiation and temperature data comes from the Open-Meteo Archive API, which provides actual recorded daily measurements aggregated from national weather services worldwide (DWD, NOAA, MeteoFrance, ECMWF, and others). City geocoding uses the Open-Meteo Geocoding API, which covers virtually every city, town, and village worldwide — sourced from the GeoNames database with millions of locations in every country. The free tier allows up to 10,000 API calls per day (5,000/hour, 600/minute), which is far more than any individual user would need. Each calculation uses just 2 API calls (one geocoding + one archive data fetch).

Supported Panel Sizes

This calculator supports 300W, 400W, 450W, and 550W standard panels, plus 650W and 750W high-configuration panels for large commercial and industrial installations. Each panel size uses accurate Vmp and Imp electrical parameters for proper charge controller string calculations.