Wind vs Solar Power: How to Compare Them

This guide walks you through comparing wind power and solar power for electricity generation, so you can weigh their costs, output, and practical fit for your situation. You’ll learn what data to gather, how to estimate annual energy production for each, and how to interpret the results. No special tools are needed beyond a calculator and your electricity bill.

What You’ll Need

• Your electricity bill (to see your average monthly or annual usage in kWh)
• Your location’s average wind speed (you can find this from local weather data or a wind map)
• Your location’s average peak sun hours per day (solar insolation maps are available online)
• A calculator or spreadsheet
• Preliminary quotes or prices for wind turbines and solar panels (optional but helpful)

Step-by-Step

1. Determine your electricity consumption. Look at your annual usage in kilowatt-hours (kWh) from your electricity bills. This is the baseline you want to offset. For example, the average US home uses about 10,000 kWh per year, but yours may differ.
2. Find your average wind speed. Use a reliable wind resource map or local weather station data to get the annual average wind speed at your site, ideally at the height where a turbine would be installed (typically 30–50 m). If you only have ground-level data, note that wind speeds increase with height.
3. Estimate wind turbine output. Use a simple formula: Annual energy (kWh) ≈ 0.01328 × (rotor diameter in meters)² × (wind speed in m/s)³ × 8760 hours × efficiency factor. A typical efficiency factor is 0.3–0.4 for small turbines. For example, a 5 kW turbine with a 4 m rotor at 5 m/s wind would produce roughly 0.01328 × 16 × 125 × 8760 × 0.35 ≈ 8,150 kWh/year. Better yet, use the power curve from the turbine manufacturer if available.
4. Find your peak sun hours. Look up the average annual peak sun hours (PSH) for your location—this is the equivalent number of hours per day of full sun. In the US, this ranges from about 3.5 in the Pacific Northwest to 6+ in the Southwest.
5. Estimate solar panel output. Use the formula: Annual energy (kWh) = system size (kW) × PSH × 365 × performance ratio. The performance ratio accounts for losses (inverter, temperature, dust) and is typically 0.75–0.85. For a 5 kW system in a location with 4.5 PSH, that’s 5 × 4.5 × 365 × 0.8 ≈ 6,570 kWh/year.
6. Compare the energy output per installed capacity. Divide the annual kWh by the system’s rated capacity (kW) to get the capacity factor. For wind, a good site might have a capacity factor of 25–35%; for solar, it’s usually 15–25% in sunny areas. This tells you how efficiently each technology uses its rated power.
7. Compare costs. Get quotes for the installed cost of each system (including permits and installation). Calculate the cost per kWh over the system’s lifetime: Lifetime cost per kWh = (installed cost + maintenance) / (annual kWh × lifespan in years). Wind turbines last 20–25 years, solar panels 25–30 years.
8. Consider space and siting. Solar panels need clear, unobstructed roof or ground area. Wind turbines need at least 30 feet of clearance above nearby obstacles and a minimum average wind speed of 5 m/s (11 mph) to be viable. Check local zoning and permitting rules.
9. Factor in reliability and intermittency. Solar produces only during daylight, wind can produce day and night but varies with weather. Think about how each aligns with your usage patterns and whether you need battery storage.
10. Make a decision matrix. Score each option on factors like cost, output, maintenance, aesthetics, and environmental impact. Assign weights based on your priorities and sum the scores to see which comes out ahead.

Common Mistakes

• Using average wind speed from a distant location. Wind is highly local; a site 10 km away can be significantly different. Use data from your exact property or a nearby weather station.
• Ignoring wind shear. Wind speed increases with height. If you compare a turbine at 10 m height with one at 30 m, the latter will produce much more energy.
• Using peak sun hours that are too optimistic. Many maps show annual averages, but actual monthly production varies. Use a conservative performance ratio (0.75) to avoid overestimating.
• Forgetting maintenance costs. Wind turbines have moving parts and may require periodic servicing; solar panels are low-maintenance but need cleaning in dusty areas.
• Comparing rated capacity instead of actual output. A 5 kW wind turbine does not produce 5 kW continuously; it produces its rated power only at a specific wind speed. Always compare annual kWh, not kW.

Tips

• Use online calculators from reputable sources (like NREL or your local utility) as a cross-check, but understand their assumptions.
• If you’re considering a hybrid system, you can size each to cover different times of day—solar for daytime, wind for night and winter.
• Check for net metering policies in your area; they affect the financial value of the energy you generate.
• Talk to local installers who have experience with both technologies. They can give you real-world performance data from nearby installations.
• For a quick rule of thumb: wind turbines generally produce more energy per installed watt in windy areas, but solar is more predictable and easier to permit in residential zones.

Troubleshooting

• Your wind speed estimate seems too low. Double-check the height at which the data was measured. If it’s at 10 m, multiply by roughly 1.2–1.4 to estimate at 30 m, depending on terrain roughness.
• Your solar output estimate is much higher than a neighbor’s actual system. Your performance ratio might be too high, or you may have shading that you didn’t account for. Use a more conservative ratio (0.7) and consider a shading analysis.
• You can’t find local wind data. Use a wind map that provides data at 50 m height, or contact a local airport for their anemometer data—though that may not represent your site.
• Your electricity usage varies a lot seasonally. Compare monthly production estimates to your monthly usage, not just annual totals. This will show whether you produce enough in winter (when solar is low but wind may be high).
• You’re unsure about the efficiency factor for wind. If you have a specific turbine model, look up its power curve and calculate the annual energy using the Weibull distribution for your site’s wind regime. For a rough estimate, 0.3 is a safe starting point.

Frequently Asked Questions

How much land do I need for a small wind turbine vs. solar panels?

A 5 kW wind turbine typically needs about 0.5 acres for the tower and setback, while a 5 kW solar array needs about 400–500 square feet of roof or ground space. Solar is easier to fit on small lots.

Which is cheaper: wind or solar per kWh?

It depends on your location. In windy areas, wind can be cheaper per kWh; in sunny areas, solar often is. On a residential scale, solar is usually less expensive to install and maintain, but wind has a higher capacity factor in good sites.

Can I combine wind and solar to reduce intermittency?

Yes, a hybrid system can smooth out production because wind often blows at night and in winter, complementing solar’s daytime peak. This can reduce battery storage needs.

How long do wind turbines and solar panels last?

Wind turbines typically last 20–25 years, while solar panels have a 25–30 year lifespan, with some degradation over time. Both require occasional maintenance, but solar is generally more reliable.

Do I need a battery with either system?

Only if you want to be off-grid or have backup power. If you’re grid-tied with net metering, you can use the grid as your battery. Batteries add significant cost to both systems.

What about noise and aesthetics?

Wind turbines produce some noise (typically 40–60 dB at 100 m) and can be visually prominent. Solar panels are quiet and can be integrated into roofs. Local regulations may restrict turbines in residential areas.

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