# Wind Turbine Savings Calculator Annual output from both nameplate rating and rotor physics, priced against your electricity rate and install cost. --- - **Canonical URL:** https://dothecalculation.com/calculators/wind-turbine-savings-calculator - **Category:** Eco & Sustainability - **Publisher:** Do The Calculation (https://dothecalculation.com) - **Cost:** Free, no account or sign-up required - **Privacy:** Runs entirely in the browser; inputs are never sent to a server - **Methodology:** https://dothecalculation.com/methodology --- ## Estimate Small Wind Turbine Output and Payback Annual energy from both the nameplate rating and the physics of the rotor, priced against your electricity rate, install cost and export tariff. - Cross-checks the manufacturer capacity factor against the swept area - Splits self-consumed and exported energy, which are worth different amounts - Honest payback: many domestic sites never repay the install, and it says so ## Quick Answer — How Much Will a Small Wind Turbine Generate? There are two ways to estimate annual output, and a domestic wind quote is only credible when they agree. The **nameplate route** is what suppliers quote: **Annual kWh = rated kW × 8,760 hours × capacity factor**. A 5 kW turbine at a 30% capacity factor produces 5 × 8,760 × 0.30 = **13,140 kWh a year**. The **physical route** is what the rotor can actually extract: **P = ½ × air density × swept area × power coefficient × wind speed³**. A 5.5 m rotor sweeps 23.76 m², and at 6.5 m/s with a power coefficient of 0.35 that is **1.40 kW** at the mean wind speed. Multiplied out across the year with a Rayleigh energy pattern factor of 1.91 — the standard correction for the fact that energy scales with the cube of speed, so windy hours count far more than the average — it gives **23,403 kWh**. Here the physics comfortably exceeds the nameplate figure, so 13,140 kWh stands. When it does not, the nameplate number was never achievable and the calculator says so. The cubed term is the single most important fact about wind. **Double the wind speed and the power goes up eightfold.** A site at 5.0 m/s and a site at 6.5 m/s are not 30% apart in output; they are roughly twice as good. ## How to Use This Calculator: A Well-Sited 5 kW Turbine Take a **5 kW turbine on a 5.5 m rotor** at a genuinely good site: **6.5 m/s** mean wind speed, a **30% capacity factor**, **$26,000** installed with a **$7,800** incentive, **$300 a year** in maintenance, electricity at **$0.19/kWh**, export at **$0.07/kWh**, **60% self-consumed**, over **20 years**. Output is **13,140 kWh** in year one, of which **7,884 kWh** offsets grid electricity at 19 cents and **5,256 kWh** is exported at 7 cents. That is **$1,866 of gross value**, or **$1,566** after maintenance. Net install cost after the incentive is **$18,200**. Payback arrives at **12.0 years**. Across the full twenty years, with 0.5% annual degradation, the turbine generates **250,684 kWh** and returns **$29,597** — leaving it **$11,397 ahead** of its net cost. The levelised cost works out at **$0.097 per kWh**, comfortably under the 19-cent grid rate. That is a good outcome, and it required a 6.5 m/s site. Note how much of the value comes from self-consumption: the 60% used on site is worth nearly three times as much per kWh as the exported 40%. Shifting loads to windy periods, or adding storage, moves that ratio and is often a better return than a bigger turbine. The [solar battery storage calculator](/calculators/solar-battery-sizing-calculator) sizes that side of the question. ## A Second Example: Why Most Domestic Sites Do Not Pay Back Now the same 5 kW turbine on an ordinary site: **5.5 m/s**, a **22% capacity factor**, **$28,000** installed with a **$7,500** incentive, **$350** maintenance, electricity at **$0.17**, export at **$0.06**, **55%** self-consumed. Output falls to **9,636 kWh** — a 27% drop from a 15% drop in wind speed, which is the cube law working against you. First-year value is **$1,161**, or **$811** after maintenance, against a net cost of **$20,500**. Over twenty years the turbine returns **$15,152** and finishes **$5,348 short**. It never pays back. Levelised cost is **$0.150 per kWh**, still under the grid rate but not by enough to cover the capital. A third case makes the point sharper. A **2.5 kW turbine on a 3.7 m rotor** at a sheltered **4.2 m/s** site, quoted at a 14% capacity factor: the nameplate figure would be 3,066 kWh, but the swept area at that wind speed can only deliver **2,857 kWh**. The calculator flags that the **physics is the binding constraint**, implying a real capacity factor of **13.0%** rather than the quoted 14%. Net cost $11,500, twenty-year return $4,068, finishing **$7,432 short** at a levelised cost of **$0.284 per kWh** — well above what grid electricity costs. This is the honest state of small-scale wind. It works at genuinely windy, unobstructed, rural sites and rarely anywhere else. For most suburban roofs the same capital in solar returns far more, which the [solar panel payback calculator](/calculators/solar-payback-calculator) will show side by side. ## Reading a Site and a Quote Everything turns on the wind speed at hub height, and almost nobody has measured it. Regional wind maps are modelled at 10 m or higher over open terrain and routinely overstate what a specific garden sees, because buildings, trees and terrain create turbulence and wind shadow far beyond their own height. A rough rule used in the industry is that a turbine wants to be 10 m above anything within 150 m of it — a condition most domestic sites fail outright. Turbulence is a second problem that output figures never capture. A turbine in disturbed air produces less than the mean wind speed suggests, yaws constantly chasing shifting direction, and wears out faster. A site with a good average speed and bad turbulence performs worse than the numbers here imply. On the quote itself, check three things. **Is the capacity factor plausible?** Small turbines at real domestic sites typically land between 10% and 25%; a quote above 30% needs a genuinely exposed rural location to justify it. **Does the swept area support it?** That is exactly the cross-check this calculator runs. **Is maintenance included in the payback?** Small wind has moving parts, bearings and a yaw mechanism, and a few hundred dollars a year of servicing is normal — leaving it out of a payback calculation shortens it by years. Planning permission, noise limits and grid connection agreements are separate hurdles that can end a project regardless of the arithmetic. And if the goal is carbon rather than money, the [carbon footprint calculator](/calculators/carbon-footprint-calculator) will tell you where a household's emissions actually sit — for many, heating and transport dwarf electricity, and the same capital spent there does more. ## Limitations The biggest simplification here is treating the wind as a single mean speed with a Rayleigh energy correction. Real sites have a wind speed distribution, and the shape of that distribution — usually described by a Weibull k parameter — changes annual output meaningfully at the same mean. Two sites averaging 5.5 m/s can differ by 15% in energy depending on whether the wind is steady or gusty. Where measured site data exists, a Weibull-based estimate from that data will beat this approximation. Cut-in and cut-out speeds are not modelled. A turbine produces nothing below roughly 3 m/s and shuts down above roughly 25 m/s for protection, and both truncations reduce real output below what a smooth calculation suggests. The power coefficient is also treated as constant, whereas real machines vary it with wind speed and hit their quoted figure only over a narrow band. The financial side assumes flat electricity and export prices across the whole analysis period. Over twenty years neither is realistic. Rising grid prices would improve every result here; a falling export tariff would worsen them. Nothing is discounted to present value either, so a twenty-year total treats a dollar in year nineteen as equal to one today. Finally, the calculator caps output at the lower of the physical and nameplate figures, which is a sanity check rather than a model of the machine. It will catch an implausible quote; it will not tell you whether a specific turbine performs to its own curve, whether the site is turbulent, or whether the tower is tall enough. A year of measured on-site wind data is the only thing that genuinely answers those questions, and for a project of this size it is usually worth the wait. ## Related Calculators The [Solar Panel Payback Calculator](/calculators/solar-payback-calculator) runs the same investment question for the technology that suits most domestic sites far better, and comparing the two side by side is usually the decisive exercise. The [Solar Panel Sizing Calculator](/calculators/solar-panel-sizing-calculator) works out how much array a given consumption needs. The [Solar Battery Storage & Backup Calculator](/calculators/solar-battery-sizing-calculator) addresses the self-consumption question that drives so much of the value here. And the [Carbon Footprint Calculator](/calculators/carbon-footprint-calculator) puts household electricity into proportion against heating and transport before any capital is committed. ## Frequently asked questions ### How much electricity does a small wind turbine produce? A 5 kW turbine at a good 6.5 m/s site with a 30% capacity factor produces about 13,140 kWh a year. The same turbine at an ordinary 5.5 m/s site with a 22% capacity factor produces 9,636 kWh. A sheltered 4.2 m/s site is worse again. Wind speed dominates everything. ### What is a realistic capacity factor for a domestic turbine? Between 10% and 25% for most real sites. Above 30% requires a genuinely exposed rural location. Any quote well above that should be cross-checked against what the swept area can physically deliver, which is what this calculator does automatically. ### Why does wind speed matter so much? Because power scales with the cube of speed. Double the wind and the power goes up eightfold. That is why a 15% drop in mean wind speed cost 27% of annual output in the second example, and why site selection matters more than turbine selection. ### How long does a wind turbine take to pay back? At a good site with an incentive, around twelve years is achievable. At an average domestic site it often never pays back inside a twenty-year life. The calculator reports honestly when the cumulative return never reaches the net install cost, because that is the common case. ### Is wind or solar better for a home? Solar, for almost every domestic site. Wind needs genuinely exposed, unobstructed, high-wind locations to compete, and most homes have none of those. Run the same capital through the solar payback calculator before committing to wind — the comparison is usually decisive. ### How high does a wind turbine need to be? An industry rule of thumb is 10 m above anything within 150 m. Buildings and trees create turbulence and wind shadow far beyond their own height, and a turbine in disturbed air produces less, wears faster, and never reaches the output its mean wind speed implies. ### Why does self-consumption matter? Because a kWh used on site is worth your full retail rate while an exported kWh earns only the export tariff — in the worked example, 19 cents against 7. Shifting loads to windy periods or adding storage often returns more than buying a larger turbine. ### What does the swept-area check tell me? Whether the quoted output is physically possible. The rotor can only extract what the wind carries through its area, and if that limit falls below the nameplate figure, the quote was optimistic. In the third example a quoted 14% capacity factor was really 13.0% once the rotor size was accounted for. ## Related concepts - **Capacity Factor** — Annual energy produced as a share of what the turbine would make running flat out all year. Small domestic turbines typically land between 10% and 25%; large onshore wind farms reach 25% to 45%. - **Swept Area** — The circle the rotor blades trace, in square metres. Power is directly proportional to it, so doubling the rotor diameter quadruples the available power at the same wind speed. - **Power Coefficient** — The share of the wind's kinetic energy a rotor actually converts. The theoretical maximum is the Betz limit of 59.3%; real small turbines achieve roughly 25% to 40%. ## Related guides - [Solar Panel Payback: ROI, Incentives, and Bill Savings](https://dothecalculation.com/blog/green/solar-panel-roi-payback-period) — Estimate solar payback by connecting installation cost, incentives, bill offset, utility-rate growth, 20-year savings, and the live DTC solar payback calculator. - [Understanding Calculator Formulas: How DTC Turns Inputs into Results](https://dothecalculation.com/blog/site-guides/understanding-calculator-formulas) — Understand how Do The Calculation formulas are presented, what the explanation blocks mean, and how to verify calculator logic before using a result in a real decision. ## Related calculators - [Solar Panel Payback Calculator](https://dothecalculation.com/calculators/solar-payback-calculator) — Estimate the return on investment and payback timeline for solar panel installation based on system cost, energy savings, and incentives. - [Solar Battery Storage & Backup Calculator](https://dothecalculation.com/calculators/solar-battery-sizing-calculator) — Size your emergency solar battery storage capacity and calculate off-grid runtime in days, with or without solar recharge during outages. - [Solar Inverter & Charge Controller Sizing Calculator](https://dothecalculation.com/calculators/solar-inverter-sizing-calculator) — Size solar inverter continuous power and charge controller current based on solar panel specs and temperature variations. - [Solar Panel Sizing Calculator](https://dothecalculation.com/calculators/solar-panel-sizing-calculator) — Calculate how many solar panels you need from your monthly usage, peak sun hours, panel wattage, and system derate factor. - [E-Bike vs Car Savings Calculator](https://dothecalculation.com/calculators/ebike-vs-car-savings-calculator) — Calculate your annual cost savings and CO2 avoided by replacing car miles with e-bike riding. - [Geothermal Heat Pump Installation ROI & Payback Calculator](https://dothecalculation.com/calculators/geothermal-hvac-payback-calculator) — Compare geothermal COP against standard heating and cooling systems to project annual utility savings, incentives, and payback. --- _Every kWh, dollar and payback figure on this page was produced by running this calculator with the stated inputs rather than estimated, including the examples that never pay back. The model treats wind as a single mean speed with a Rayleigh energy correction rather than a full Weibull distribution, so two sites with the same average can differ by around 15% in real output. Cut-in and cut-out speeds are not modelled, the power coefficient is held constant, and electricity and export prices are assumed flat with no discounting. A year of measured on-site wind data is the only reliable basis for a project of this size._ --- _Source: [Do The Calculation](https://dothecalculation.com/calculators/wind-turbine-savings-calculator). Quote freely with attribution and a link to this page._