DIY Home Solar Panel Sizing Calculator for Mediterranean Climates

Introduction

Homeowners in Or Akiva, Tel Aviv, Athens and beyond often ask, “How many panels do I need for 4 kWh daily?” Yet most online tools cater to U.S. conditions and ignore our high irradiance, seasonal variation, and local costs. This guide provides a free, locale-specific spreadsheet and an in-page calculator—consider it your solar goldmine.

Why a Localized Calculator Matters

• Average Irradiance: Mediterranean climates receive 5–6 kWh/m²/day, far above U.S. averages.
• Roof Angles: Optimal tilt (25°–35°) boosts yield by up to 15%.
• Seasonal Variation: Winter yields drop ~30%, summer peaks +25%.

How It Works

Our calculator factors:

• Daily kWh requirement (your past bills or estimations).
• Average solar irradiance in your locale.
• Panel wattage (e.g., 300 W).
• System loss factor (temperature, wiring, inverter; ~20%).
• Cost per panel & electricity rate for payback estimates.

Solar Panel Sizing Calculator

Step-by-Step Spreadsheet Guide

Prefer offline tools? Download our free Excel/Google Sheets template, pre-loaded with formulas and graphs. To customize:

1. Enter your historical daily kWh in the “Usage” tab.
2. Adjust Irradiance and Loss sliders.
3. View dynamic charts on the “Results” tab, showing monthly yield.
4. Export to PDF for quotes and permits.

Troubleshooting & FAQs

Why does my payback say >20 years?

High cost inputs or low electricity rates inflate payback. Verify your rate and get volume discounts on panels (bulk kits).

How accurate is irradiance?

We use PVGIS and NASA’s Surface Meteorology data for Mediterranean sites—within ±5% accuracy.

Can I add a battery?

Yes—extend payback by factoring battery cost and efficiency. Our template includes a “Battery” tab for this.