Solar Panel System Size Estimator
Use this tool to estimate how many solar panels you need based on your monthly energy use and sunlight. It's designed for homeowners, businesses, and even boat or van owners to make smart solar choices.
How It Works
- How do I know my electricity use?
Check your latest utility bill. Look for a line that says “kWh used this month.” If you have no bill, a U.S. average household uses 877 kWh/month. - What are sun hours?
It's the average number of usable solar hours per day. A sunny state like Arizona may get 6–7, while cloudy regions might get 3–4. Use Global Solar Atlas for a quick check. - What is panel wattage?
Most solar panels are rated between 350W–400W. This means under ideal sun, one panel gives 350–400 watts per hour. - What does system efficiency mean?
Not all energy reaches your appliances. Wiring, shading, dust, and heat reduce efficiency. Most homes assume 75–85% system efficiency. - How much roof space do I need?
Each 400W panel needs approx. 1.8m² (20 sq ft). The calculator gives you a total estimate.
New: Free Solar Estimator Guide
See real-world examples of how the tool works for homes, boats, cabins, and more — plus how to plan your solar setup in minutes.
📘 Read the Full GuideTop Off-Grid Solar Kits
Frequently Asked Questions
This depends on your sun hours and panel wattage. Use the calculator above to get your exact recommendation.
Most areas get 3–6 hours per day. Use 4.5 as a safe average or look it up using solar maps.
Batteries store energy for nighttime or power outages. Not required for grid-tied homes, but great for boats, cabins, or off-grid living.
Yes, DIY solar kits exist and can be much cheaper. Always follow safety codes and consider pro help if unsure.