Fast ways to estimate roof solar potential
A quick estimate of roof solar potential can be made using a few simple observations and online tools. This helps decide whether a deeper site assessment is worthwhile.
Steps for a quick estimate:
- Measure usable roof area: Walk around or use satellite imagery to estimate the square footage of roof space free from obstructions.
- Determine orientation and tilt: Note which roof faces south, east, or west and approximate the slope. South-facing and moderate slopes often perform best in the northern hemisphere.
- Check for shading: Observe shading during midday in different seasons. Trees, chimneys, and adjacent buildings that cast shade reduce potential.
- Use rule-of-thumb conversion: A common heuristic is that 100 square feet of good roof area can support roughly 1 kilowatt (kW) of solar, depending on panel efficiency.
Online and app tools
- Satellite-based solar calculators estimate rooftop potential using aerial imagery and local solar resource data.
- Some solar companies offer free rooftop assessments showing likely panel layouts and estimated annual production.
Estimating energy production
- Multiply estimated system size (kW) by local average peak sun hours or by a site-specific production factor (for example, 1 kW may produce 1,000–1,500 kWh per year depending on location).
- Local solar maps and databases provide average insolation values for planning.
Why a professional assessment still matters
Quick estimates are useful for initial screening but can miss important details like structural constraints, exact shading patterns, permit limitations, and electrical considerations. For an accurate proposal and financial estimate, schedule a professional site survey.