"The question you're asking is an important one, and it's worth separating the engineering reality from the marketing.

A wind turbine is not energy-free simply because it generates electricity without burning fuel. Its true energy cost includes the extraction and processing of raw materials, manufacture of components, transportation, construction, maintenance, replacement parts, and eventual dismantling or recycling.

The relevant calculation is called Energy Return on Energy Invested (EROEI), or sometimes Energy Payback Time.

There are two questions worth answering:

1. How much energy does it take to produce, install, maintain and eventually dispose of a wind turbine?

2. How much usable electricity does it generate over its actual working lifetime?

The ratio between those figures tells us how much net energy society actually receives.

1. What does it take to manufacture one?

Let's use a modern, utility-scale, land-based 2 MW wind turbine as our reference. This is a useful comparison because several published lifecycle studies examine turbines of this size.

A turbine isn't just a steel tower and three blades. Its material inventory includes:

An interesting point: in a Vestas lifecycle assessment of its 3.3 MW turbine, steel and iron account for approximately 82% of turbine mass. When the foundations are included, concrete accounts for approximately 66% of the entire installation's mass.

The mining and processing of these materials are not trivial. Iron ore must be mined, concentrated and smelted; copper ore must be mined, crushed, concentrated and refined; and the production of aluminium and composite materials is energy intensive.

One important qualification: lifecycle assessments generally account for the energy used in producing these materials, rather than simply adding up the electricity consumed at the turbine factory. Some of that energy comes from coal, natural gas and other fuels.

2. How much energy does it take?

There are several published lifecycle assessments worth examining.

These studies include varying combinations of manufacturing, transportation, installation, maintenance and end-of-life treatment.

The consistent finding is that manufacturing accounts for the largest share of the energy investment. One 2 MW study attributed 84.4% of lifecycle energy requirements to manufacturing, with tower construction particularly significant.

3. Now let's calculate the actual lifetime return

Consider a 2 MW turbine operating at a 35% average capacity factor.

That means it produces, on average, 35% of its theoretical maximum output.

6,132,000 kWh

Annual electricity production

Assuming a 20-year working life:

122,640,000 kWh

Total lifetime electricity production

Now let's apply the published energy payback figures.

A seven-month payback at this production rate represents approximately:

So, as an illustrative electricity-equivalent calculation:

• Energy invested: approximately 3.58 million kWh.

• Lifetime generation: approximately 122.64 million kWh.

• Energy returned: approximately 34 times the initial investment.

Illustrative 2 MW turbine energy balance

20-year lifetime at 35% capacity factor; 7-month energy payback assumption.

 

4. What does this mean over its lifetime?

Important technical qualification: The calculation above translates the seven-month payback assumption into an electricity-equivalent figure. Published lifecycle studies don't all use identical energy accounting conventions. Some count primary energy consumed in producing fuels and electricity, while the output is measured as electricity. Therefore, 3.58 million kWh should be treated as an illustrative estimate, not a measured manufacturing electricity bill.

Also, this is a turbine-level calculation. It does not necessarily include the full cost of grid expansion, transmission, backup generation, or additional storage needed to accommodate variable generation.

5. What about recycling?

This is where things get interesting.

Steel, copper and aluminium are recyclable, and recycling can substantially reduce the energy required for future manufacturing.

However, there are complications:

• Steel and copper can be recovered and reused relatively effectively.

• Rare-earth magnets can be recycled, but recovery is more complicated.

• Fibreglass and carbon-fibre blades are considerably more problematic.

• Concrete foundations are generally demolished, with material often downcycled rather than returned to equivalent-quality concrete production.

A 2012 lifecycle study examined recycling scenarios and found that recycling improved the energy balance.

In other words, a turbine doesn't simply disappear when its useful life ends. There is an additional industrial process involved in dealing with it.

6. Where I think the real questions lie

I wouldn't conclude from these figures that wind power is an energy scam. The available lifecycle research suggests that properly sited, utility-scale wind turbines produce considerably more energy than is invested in them.

But I would raise four important questions that often get lost in the public discussion:

1. Location matters enormously.

A turbine in a consistently windy location can repay its energy investment relatively quickly. Put the same turbine somewhere with mediocre wind resources and its economics and energy return deteriorate.

2. What happens after 20–25 years?

The foundation and tower may remain serviceable, but blades, generators, gearboxes and other components may need replacement. Repowering is not free.

3. What is the cost of intermittency?

A turbine produces electricity when the wind blows, not necessarily when electricity is needed. Storage, transmission and balancing systems have their own material and energy costs. These are not always fully allocated to individual turbine lifecycle assessments.

4. What is the actual environmental cost of mining?

The extraction of copper, iron, aluminium, rare earths and other minerals has environmental consequences beyond energy consumption: tailings, water use, habitat disturbance, chemical processing and waste.

These deserve scrutiny even if the energy balance is positive.

My conclusion

The best available lifecycle studies suggest that a modern, well-sited, large wind turbine typically repays its embodied energy in roughly 5–12 months, and then generates net energy for the remainder of its working life.

That is a reasonably impressive energy return.

But I would be cautious about accepting a turbine's published energy-payback figure as the complete environmental balance of a wind farm or an electricity system.

There is a substantial difference between:

• A turbine being energy-positive.

• A wind farm being environmentally sustainable.

• A national electricity grid being economically and technically sustainable with a high proportion of wind power.

Those are three different propositions.

One further investigation I think would be particularly worthwhile: comparing the full cradle-to-grave energy and material costs of wind, solar, hydroelectric, nuclear, natural gas and coal, using the same accounting boundaries and equivalent electricity output.

That would give us a much more meaningful comparison than simply labelling one technology green and another dirty."

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So I was wrong. I'm actually glad.