Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Electrical & Wiring
How Many Solar Panels Do I Need? Calculator
Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
Estimate panel count and payback from usage and production assumptions. Planning estimates only — verify measurements and local codes on site.
Inputs
1005000
300600
28
5000100000
0.050.5
Smart analysis
Recommendations
Tailored to your live inputs and result—guidance only, not professional advice.
- Interpret
Treat this as a planning estimate
Primary result: Panels needed = 15. Re-run with optimistic and pessimistic inputs to understand the range—not just a single point.
Scenario studio
Compare A vs B
Capture two sets of inputs on this device, then see which outcome wins. Share either scenario with a link.
Scenario A
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Scenario B
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Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Monthly kWh usage
The “Monthly kWh usage” value used in this tool’s formula. Adjust it to see results update live.
Panel watts
The “Panel watts” value used in this tool’s formula. Adjust it to see results update live.
Peak sun hours/day
The “Peak sun hours/day” value used in this tool’s formula. Adjust it to see results update live.
System cost
One-time or recurring costs that affect total money paid.
Utility rate ($/kWh)
The “Utility rate ($/kWh)” value used in this tool’s formula. Adjust it to see results update live.
- systemCost
System cost ($)
The “System cost ($)” field. Default 18000; typical range 5000–100000.
How this calculator works
Estimate panel count and payback from usage and production assumptions. Planning estimates only — verify measurements and local codes on site. Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings. Example: 900 kWh/mo, 400 W panels, 5 sun hrs → ~15 panels; payback depends on rate.
Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
Example: 900 kWh/mo, 400 W panels, 5 sun hrs → ~15 panels; payback depends on rate.
When to use this Solar Panel Array
Common use cases
- Estimate panel count and payback from usage and production assumptions.
- Sanity-check with this case: 900 kWh/mo, 400 W panels, 5 sun hrs → ~15 panels; payback depends on rate.
- The relationship is: Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
Localized examples
- Electrical & Wiring: the example on this page uses the same formula as the widget.
What you get
- Fields: Monthly kWh usage, Panel watts, Peak sun hours/day, System cost ($)
- Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
- Example on the page: 900 kWh/mo, 400 W panels, 5 sun hrs → ~15 panels; payback depends on rate.
How to Calculate Solar Panel Array Step-by-Step
- 1Enter Monthly kWh usage, Panel watts, Peak sun hours/day, then the remaining fields. Use the values you have, not a catalog average, unless that is all you know.
- 2Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
- 3Worked case: 900 kWh/mo, 400 W panels, 5 sun hrs → ~15 panels; payback depends on rate.
- 4Buy materials after you walk the job. This is a first-pass quantity, not a purchase order.
Governing formula
Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
900 kWh/mo, 400 W panels, 5 sun hrs → ~15 panels; payback depends on rate.
Example: set Monthly kWh usage = 900, Panel watts = 400, Peak sun hours/day = 5, then read the result.
Variable definitions
- monthlyKwh
Monthly kWh usage
The “Monthly kWh usage” field. Default 900; typical range 100–5000.
- panelWatts
Panel watts
The “Panel watts” field. Default 400; typical range 300–600.
- sunHoursPerDay
Peak sun hours/day
The “Peak sun hours/day” field. Default 5; typical range 2–8.
- systemCost
System cost ($)
The “System cost ($)” field. Default 18000; typical range 5000–100000.
- kwhRate
Utility rate ($/kWh)
The “Utility rate ($/kWh)” field. Default 0.14; typical range 0.05–0.5.
- The takeoff (Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.) ignores waste, code, and what you find when you open the wall. Measure twice on site.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Panels = monthly kWh ÷ (panel W × sun hrs × 30 ÷ 1,000); payback = cost ÷ annual savings.
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Community
Reviews & Ratings
See what others think about this tool, then leave your own rating to help improve CalculioHub.
4.8
out of 5.0
4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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