PVGIS Off-Grid Calculator: Sizing Batteries for Remote Homes in Paris (2025 Guide)

Why PVGIS for Off-Grid Solar Planning in Paris?

PVGIS stands out as the most reliable free tool for off-grid solar calculations in Europe. Unlike generic calculators, it uses satellite-derived solar radiation data specific to Paris's climate, considering seasonal cloud cover, atmospheric conditions, and the city's geographic location at 48.8566° N latitude.

For off-grid homes in Paris and surrounding areas, this precision matters. The platform calculates how much solar energy your panels will generate month by month, then determines the battery capacity needed to bridge periods of low sunlight, particularly during Paris's overcast winter months.

The tool is completely web-based, requiring no software installation, and provides professional-grade results used by solar engineers across Europe.

Understanding Off-Grid Solar Requirements in Paris

Before diving into PVGIS, you need to understand what makes off-grid solar design different from grid-tied systems. In Paris, where winter days are short and cloudy weather is common from November through February, your battery bank must store enough energy to power your home during extended periods without adequate solar generation.

Key factors affecting off-grid systems in Paris:

Paris receives approximately 1,700 kWh/m² of annual solar radiation, with significant seasonal variation. July averages 5.5-6 peak sun hours daily, while December drops to just 1-1.5 peak sun hours. Your system must be sized for the worst-case scenario, not the summer average.

Battery autonomy—the number of days your batteries can power your home without solar input—is critical. Most Paris-based off-grid systems require 2-3 days of autonomy to account for consecutive cloudy days, which are frequent during winter.

System losses from temperature effects, battery inefficiency, and cable resistance typically reduce available energy by 20-25% in real-world conditions. PVGIS accounts for these factors in its calculations.

Step-by-Step: Using PVGIS Off-Grid Calculator for Paris

Step 1: Select Paris Location

Navigate to the PVGIS website and access the off-grid PV system calculation tool. You can select Paris by entering the coordinates (48.8566° N, 2.3522° E) directly or by clicking on Paris in the interactive map interface.

The platform automatically loads solar radiation data for your selected location, including monthly averages and historical weather patterns. For remote homes outside central Paris, zoom in to pinpoint your exact location, as terrain and local conditions can affect solar availability.

Step 2: Define Your Daily Energy Load

Calculating your daily load is the foundation of proper battery sizing. For a small off-grid cabin in Paris, a typical baseline might be 5 kWh per day, covering essentials like lighting (0.5 kWh), refrigeration (1.5 kWh), laptop and devices (0.8 kWh), water pump (0.5 kWh), and basic appliances (1.7 kWh).

For a full-time residence, daily loads typically range from 8-15 kWh, depending on heating method, appliance efficiency, and lifestyle. PVGIS allows you to input your average daily consumption in kWh, which it uses as the basis for all calculations.

Be realistic and slightly conservative with your load estimate. It's better to oversize your system slightly than to run short of power during critical winter months.

Step 3: Configure Solar Panel Specifications

Input your planned solar array details, including total peak power (in kWp), panel mounting angle, and azimuth (orientation). For Paris, optimal fixed mounting is typically 35-38 degrees tilt facing south (azimuth 0°), which balances summer and winter production.

PVGIS offers preset mounting configurations or custom options. For off-grid systems, a slightly steeper angle (40-45°) can boost winter production when you need it most, though this reduces summer output moderately.

The calculator also lets you specify system losses from factors like temperature, cables, and inverter efficiency. A default setting of 14% is reasonable for well-designed systems with quality components.

Step 4: Configure Battery Settings

This is where PVGIS's off-grid calculator truly shines. Select your battery type from the dropdown menu—lithium-ion batteries are increasingly popular for off-grid applications due to their deeper discharge capability, longer lifespan, and higher efficiency compared to traditional lead-acid batteries.

Battery configuration parameters:

Set your days of autonomy based on Paris's climate. Two days of autonomy is minimum for most applications, providing enough buffer for a couple of overcast days. Three days offers greater security, especially for critical loads, but increases system cost proportionally.

Specify your battery's depth of discharge. Lithium batteries can safely discharge to 80-90%, while lead-acid batteries should only discharge to 50% to preserve longevity. PVGIS uses this to calculate the usable capacity needed.

Battery charge efficiency (typically 85-95% for modern batteries) and discharge efficiency (90-98%) account for energy losses during the charge-discharge cycle. The calculator factors these losses into the final battery size recommendation.

Step 5: Run the Off-Grid Simulation

Once all parameters are entered, click "Calculate" to generate your results. PVGIS processes your inputs against its solar radiation database and produces a comprehensive analysis of your off-grid system performance.

The simulation output includes recommended battery capacity in kWh, monthly energy production and consumption data, system deficit periods (when solar production falls short of load), and the percentage of time your system will meet your energy needs without backup generation.

For a 5 kWh daily load in Paris with a properly sized system, PVGIS typically recommends 8-12 kWh of battery capacity (usable capacity, not total), depending on your autonomy setting and system configuration.

Interpreting Your PVGIS Results for Paris

The results page provides both numerical data and graphical representations of your system performance. Pay close attention to the monthly energy balance chart, which shows the relationship between solar production and your load throughout the year.

Critical metrics to evaluate:

The battery capacity recommendation from PVGIS represents the minimum usable capacity needed to meet your autonomy requirements. Remember this is usable capacity—if you specify 80% depth of discharge for lithium batteries, you'll need to purchase batteries with total capacity 25% larger than the PVGIS recommendation.

The energy coverage percentage indicates how often your solar system alone can meet your needs without backup generation. For Paris, well-designed off-grid systems typically achieve 85-95% coverage, meaning you might need backup power (generator or grid connection) for 5-15% of the year, primarily during December and January.

Monthly shortage values reveal when your system is most likely to fall short. In Paris, December and January almost always show deficits for conservatively sized systems. This is normal and expected—you can either oversize your system dramatically (often impractical and expensive) or plan for minimal backup power during these months.

Seasonal Considerations for Paris Off-Grid Systems

Paris's seasonal solar variation presents the primary challenge for off-grid system design. Summer months (May through August) generate surplus energy, while winter months (November through February) struggle to meet daily loads even with adequately sized battery banks.

During June and July, your system may generate 3-4 times your daily consumption, leaving batteries fully charged by mid-morning. This excess energy is essentially wasted in a pure off-grid system unless you have flexible loads (like water heating or air conditioning) that can absorb surplus production.

Conversely, December and January pose the opposite problem. With only 1-1.5 peak sun hours daily and frequent multi-day overcast periods, even a well-sized system may only generate 30-40% of your daily needs during the darkest weeks. Your battery bank buffers these deficits, but extended cloudy periods will eventually deplete storage.

Smart off-grid system owners in Paris adapt their energy consumption seasonally, using more power during abundant summer months and practicing conservation during winter scarcity. This behavioral adaptation significantly improves system reliability without expensive oversizing.

Optimizing Battery Size vs. Cost

PVGIS gives you the technical minimum battery capacity, but the optimal size depends on your priorities and budget. Batteries represent 30-40% of total off-grid system costs, so sizing decisions have major financial implications.

Sizing strategies for Paris installations:

The minimum viable approach uses PVGIS's recommended capacity with 2 days of autonomy and accepts that you'll need backup power 10-15% of winter days. This minimizes upfront costs but requires maintaining a generator or having grid backup available.

The balanced approach adds 20-30% capacity beyond PVGIS recommendations, providing 2.5-3 days of autonomy. This reduces backup power needs to 5-8% of the year, mostly during the darkest two weeks of December, offering a good compromise between cost and independence.

The maximum independence approach sizes batteries for 3-4 days of autonomy and may slightly oversize the solar array to boost winter production. This achieves 95-98% energy independence but can double battery costs compared to the minimum approach.

For most Paris-area remote homes, the balanced approach offers the best value, providing reliable power year-round while keeping costs reasonable and system size manageable.

Exporting and Analyzing PVGIS Data

PVGIS allows you to export detailed calculation results in CSV format, enabling deeper analysis in spreadsheet software. The export includes monthly solar radiation data, energy production estimates, load requirements, and battery state of charge simulations.

Downloading this data is valuable for several reasons. You can create custom visualizations of your system performance, share detailed specifications with installers or electricians for quote purposes, compare different system configurations side-by-side, and document your design process for permitting or insurance purposes.

The CSV export includes hourly simulations for a typical year, showing exactly when your system produces surplus energy and when it draws from batteries. This granular data helps identify opportunities for load shifting—moving flexible energy consumption to high-production periods.

For those planning DIY installations, the exported data serves as a comprehensive design specification, detailing required panel capacity, battery size, charge controller specifications, and expected performance metrics.

Common Mistakes to Avoid with PVGIS

Even with an excellent tool like PVGIS, several common errors can lead to undersized or improperly configured systems. Understanding these pitfalls helps ensure your off-grid installation performs as expected.

Frequent calculation mistakes:

Underestimating daily load is the most common error. People often calculate only essential appliances while forgetting about phantom loads, occasional high-draw devices, and seasonal variations in usage. Always add a 15-20% buffer to your estimated daily consumption.

Using annual average solar data instead of worst-case winter data leads to systems that work beautifully in summer but fail during winter. PVGIS prevents this error by showing monthly breakdowns, but you must pay attention to winter performance specifically.

Confusing total battery capacity with usable capacity creates significant sizing errors. If PVGIS recommends 10 kWh of usable capacity and you're using lithium batteries discharged to 80%, you need to purchase at least 12.5 kWh of total battery capacity.

Neglecting to account for system aging and degradation means your perfectly sized new system will be undersized in 5-7 years. Battery capacity declines over time, and solar panels lose 0.5-1% efficiency annually. Building in 10-15% excess capacity accounts for this degradation.

Beyond the Calculator: Real-World Implementation

PVGIS provides the theoretical foundation for your system, but successful off-grid living in Paris requires considering practical implementation factors beyond the calculator's scope.

Wire sizing and voltage drop matter significantly in off-grid systems where every watt counts. Using undersized cables between your solar array and batteries can waste 5-10% of your production through resistive losses. Professional installation following electrical codes is essential.

Charge controller selection impacts system efficiency substantially. Maximum Power Point Tracking (MPPT) controllers extract 15-25% more energy from your panels compared to basic PWM controllers, especially during Paris's suboptimal conditions of overcast skies and low sun angles.

Temperature effects on batteries are significant in unheated spaces. Lithium batteries perform well across wide temperature ranges, but lead-acid batteries lose substantial capacity below 10°C, common in unheated Paris outbuildings during winter. Your installation location affects real-world battery performance.

Regular maintenance and monitoring extend system life and catch problems early. Installing a battery monitor that tracks charge/discharge cycles, state of charge, and system voltages helps identify issues before they cause power failures.

PVGIS Reliability and Data Sources

PVGIS's accuracy for Paris off-grid calculations stems from its robust data sources and scientific methodology. The platform uses satellite-derived solar radiation measurements from multiple sources, validated against ground-based monitoring stations across Europe.

For Paris specifically, PVGIS draws on over 15 years of historical climate data, capturing year-to-year variations in solar availability and weather patterns. This long-term dataset ensures recommendations aren't based on anomalous years but reflect typical conditions you'll actually experience.

The European Commission's Joint Research Centre maintains and continuously updates PVGIS, incorporating new satellite data and refining calculation algorithms. This institutional backing provides confidence that the tool will remain available and accurate for years to come.

Independent comparisons between PVGIS predictions and actual system performance show accuracy within 5-8% for European locations, making it one of the most reliable free solar calculators available. For Paris installations, real-world results consistently align closely with PVGIS estimates when systems are properly installed and maintained.

Frequently Asked Questions

What battery size is needed for off-grid solar in Paris using PVGIS?

PVGIS estimates 8-12 kWh battery capacity for a 5 kWh daily load in Paris, depending on autonomy days and seasonal factors. Winter requirements drive sizing due to Paris's limited solar production from November through February.

Systems with 2 days of autonomy typically need 8-10 kWh, while 3-day autonomy systems require 10-12 kWh of usable battery capacity. Remember to account for depth of discharge limits—lithium batteries at 80% DOD or lead-acid at 50% DOD—when selecting total battery capacity.

How does PVGIS calculate off-grid battery needs?

PVGIS uses solar radiation data specific to Paris, your daily energy load, and selected autonomy settings to estimate required battery size.

The calculator simulates your system performance hour-by-hour throughout a typical year, tracking when solar production exceeds load (charging batteries) and when load exceeds production (discharging batteries).

It factors in Paris's weather patterns, including consecutive cloudy days, to determine the minimum battery capacity that maintains power reliability according to your autonomy setting. Temperature effects, battery efficiency, and system losses are incorporated into the final recommendation.

Is PVGIS reliable for Paris off-grid systems?

Yes, PVGIS is highly reliable for Paris off-grid calculations, using validated satellite data and local climate information for accurate energy estimates. The platform's predictions for Paris installations typically match real-world performance within 5-8%, provided systems are properly installed and maintained.

The European Commission maintains the database with continuous updates, ensuring data quality and accuracy. Thousands of successful off-grid installations across Europe have been designed using PVGIS, confirming its reliability for residential and commercial applications.

Conclusion: Planning Your Paris Off-Grid System

PVGIS provides the technical foundation for successful off-grid solar in Paris, but remember it's one tool in a comprehensive planning process. Use the calculator's recommendations as a starting point, then consider your specific circumstances, risk tolerance, and budget to finalize your design.

For remote homes in the Paris region, properly sized battery storage combined with adequate solar capacity creates reliable off-grid power 85-95% of the year. The remaining 5-15% typically falls during the darkest winter weeks and can be covered with minimal backup generation or temporary load reduction.

The beauty of PVGIS is that it's free, accurate, and accessible to anyone planning an off-grid system. Whether you're designing a weekend cabin, a full-time remote residence, or a backup power system, investing 20 minutes in PVGIS calculations can save thousands in oversized equipment or prevent the frustration of an undersized system.

Start your off-grid journey with confidence—input your Paris location into PVGIS, follow the steps outlined in this guide, and you'll have a scientifically sound battery sizing recommendation tailored to your specific needs and local solar conditions.