Solar System Size Calculator
Find out how many solar panels you need based on your electricity use
How to use this calculator
Fullstack Roofing Team here—follow these steps to get a solid estimate:
- Enter your average monthly electric bill (or monthly kWh).
- Adjust electric rate and peak sun hours if needed (defaults are Utah-friendly).
- Click Calculate to see recommended system size, panel count, and cost range.
Use your last 12 months of bills and average them for the best estimate.
Utah average ~$0.10–0.12/kWh
Utah ~5.5–6.2; adjust for shade or location
How solar system sizing works in Utah
Sizing a solar system in Utah requires looking at two main factors: your annual kWh usage and your roof's "solar window." Most residential systems in Utah range from 5 kW to 12 kW.
- Energy Independence: Most homeowners aim for 100% offset—meaning the system produces as much electricity as you consume over a year.
- Sun Hours: Utah is high-desert, averaging 5.5 to 6.2 peak sun hours per day. This intensity means you need fewer panels than someone in the Pacific Northwest for the same output.
- Efficiency Loss: Our calculator assumes a 15% system loss for factors like inverter efficiency, dust, and temperature.
Why roof condition matters for system size
You can't just put panels anywhere. The usable space on your roof determines your actual max system size.
We use a roof-first approach. Before we recommend a system size, we verify that your roof has at least 15–20 years of life left. Installing a 30-panel system on a 15-year-old shingle roof is a recipe for a costly detach-and-reset project in just a few years.
Frequently Asked Questions
What is the "average" solar system size for a Utah home?
A typical 2,500 sq ft home in Utah usually needs a 7 kW to 9 kW system (approx. 18–24 panels) to offset a $120–$150 monthly electric bill.
Does snow affect my solar production calculations?
Yes, but less than you might think. Snow usually slides off glass panels quickly, and cold temperatures actually help panels operate more efficiently once they are clear. We factor seasonal variation into our annual averages.
How much does a 10 kW solar system cost in Utah?
In 2024, a 10 kW system typically costs between $25,000 and $35,000 before incentives. With the 30% federal tax credit (ITC), the net cost drops significantly.
Get a precise solar layout
Calculators give you a ballpark. Our team provides a full shade analysis, roof-readiness check, and clear ROI projection.