Solar Panel Calculator

Our solar panel calculator uses a straightforward formula to estimate the right system size for your home or business. We take your monthly electricity consumption (in kWh) and divide it by your state's average peak sun hours per day, multiplied by 30 days, with an 80% system efficiency factor that accounts for real-world conditions like inverter losses, temperature effects, wiring losses, and minor shading.

You can enter your usage as a monthly electric bill amount (we convert it using your state's average electricity rate), monthly kWh, or annual kWh. Check your utility bill or online account for the most accurate numbers. Annual kWh is often the most accurate since it averages out seasonal variation.

Panel count is based on standard 400-watt monocrystalline panels, which are the most commonly installed residential panels today. Your actual installation may use different wattages (350W-450W) depending on roof space, budget, and equipment availability.

Once you know your system size, the next step is getting the proper permits. Nearly every jurisdiction in the United States requires a building permit and electrical permit before solar panels can be installed. The permit process ensures your system meets local building codes, fire safety requirements, and electrical standards.

A solar permit application typically requires a plan set that includes site plans, electrical diagrams, structural details, and equipment specifications. This is where our solar design services come in — we create professional, permit-ready plan sets that AHJs (Authorities Having Jurisdiction) accept.

For residential solar installations, your plan set will include roof layout, electrical single-line diagrams, structural attachment details, and fire setback compliance. For commercial solar projects, additional engineering calculations and PE stamps are often required.

• Roof orientation and tilt: South-facing roofs at a 30-degree tilt produce the most energy. East/west-facing roofs may need 10-20% more panels.
• Shading: Trees, chimneys, and neighboring buildings can reduce output. A site survey identifies shading issues.
• Roof type: Different roof materials (asphalt shingle, metal, tile, flat/TPO) require different mounting hardware, which affects structural requirements in your permit plans.
• Local climate: States like Arizona and California get 5.5-6.5 peak sun hours per day, while northern states like Michigan or Ohio get 3.5-4.0 hours.
• Energy goals: Some homeowners want to offset 100% of their usage, while others target 70-80% to optimize their return on investment.
• Net metering policies: Your utility's net metering program determines how excess energy is credited back to you, which affects the ideal system size.

Now that you know your estimated system size, here's how to move forward with your solar project:

1. Submit your project details — provide your address, roof type, and system specs so we can create your permit plans.
2. Receive your quote — we'll review your project and send a customized quote for your plan set.
3. Get your permit-ready plans — our team designs your plan set including site plans, electrical diagrams, and structural details.
4. Submit for permit — take your completed plan set to your local building department for permit approval.

Have questions about the process? Check out our blog for guides on solar permitting, or contact us directly. You can also call us at (720) 703-9628.