What is repowering, in one sentence?

It is rebuilding an existing wind farm with newer, usually larger turbines while reusing the land, roads, and grid connection. The goal is more output from the same site. It is different from building a brand new farm somewhere else.

Does repowering add new power to the grid?

Usually yes, because the new turbines are more productive, but the gain varies by project. Some repowers roughly hold capacity while raising how much energy the farm produces over a year. You can compare the before and after in federal generator data.

Why not just build a new farm instead?

A new farm has to clear siting, leases, permits, and a long interconnection queue, which can take years. A repowered farm already holds all of that. That is often the deciding factor, though not always.

How can I check a farm's age and size myself?

Start with the Energy Information Administration's generator data, which lists each unit's online year and nameplate capacity. Cross-check against PJM and federal filings. Treat developer pages as claims to verify, not as the final word.

The oldest wind farms in Illinois are being rebuilt, not retired

I.What repowering actually means

Repowering is what it sounds like. The developer keeps the land leases, the access roads, the substation, and the connection to the grid, then swaps out the old turbines for a smaller number of larger, more productive machines. At Mendota Hills the original fleet was dozens of small turbines rated at under a megawatt each. The rebuild replaced them with fewer units, each one taller and rated higher.

The appeal is mostly about what you avoid. A new farm has to find a site, sign leases, win local permits, and wait years in the interconnection queue (the line power projects stand in before they are allowed to plug into the grid). A repowered farm already holds those things. It reuses a spot the wind has already proven.

II.The honest math, and where to check it

Here are the numbers, hedged, because the exact figures move with every filing. At last public report the original Mendota Hills ran on the order of sixty-plus turbines for roughly 50 megawatts of nameplate capacity. The repowered farm uses far fewer turbines for something in the neighborhood of 75 megawatts. Call it more power from fewer towers, and treat any precise figure you see as a snapshot.

You do not have to take a developer's word for any of it. The federal Energy Information Administration publishes generator-level data, plant by plant, with the online year and nameplate capacity for each unit, so you can see the vintage and size for yourself. PJM's planning records show how the project connects, and federal filings round out the ownership picture. When two of those sources disagree, the government data is usually the one to trust on capacity and age.

III.Who actually makes the call

Ownership drives the decision to rebuild rather than retire: EDP Renewables North America operates a number of wind farms across Illinois and the Midwest. The grid side runs through PJM, which has to study how a resized project affects the lines around it. None of that happens on the county road where the turbines stand.

Siting rules have shifted, too. Illinois moved much of the authority for permitting wind and solar toward the state in recent years, which limits how far a county can go to block or shrink a project. For a ratepayer, the thing to watch is less the single farm and more whether repowering keeps cheap, already-connected capacity on the system instead of letting it age out.

IV.Worth watching this month

1. The Energy Information Administration's next generator data update, which is routine but the cleanest place to confirm any repowered farm's new capacity and online year.

2. PJM's interconnection and planning reports, worth a look mainly if you want to see how resized projects move through the queue.

3. Any Illinois Commerce Commission filings touching wind projects in the ComEd zone, most of which are routine but some of which signal real changes.

4. Federal Treasury and IRS guidance on the tax-credit rules for repowered projects, which genuinely matters because it shapes whether rebuilding pencils out.

5. EDP Renewables' own project pages, useful for the developer's claimed figures as long as you check them against the government data.

The oldest wind farms in Illinois are being rebuilt, not retired

I.What repowering actually means

II.The honest math, and where to check it

III.Who actually makes the call

IV.Worth watching this month

Questions readers have asked

Sources of record