If you're comparing towns in central Lake County, you've probably seen the $1.4 billion figure tied to the T5 data center campus in Grayslake. Two Grayslake addresses can sit a mile apart and still have different sets of taxing districts printed on their bills, so the number doesn't land on every Grayslake home in the same way.
Here's what's settled as of early October 2026. On September 1, the Village issued a building permit for an 800,000-square-foot first building at T5@Chicago IV. The building is part of a planned 472-acre campus along Peterson Road west of Route 83. The Village says the project came "without local municipal tax incentives, tax exemptions or TIF (tax increment financing) subsidies." It projects $1.4 billion in property tax revenue over 20 years "across local taxing bodies."
The key words are "across local taxing bodies." Your bill is built from those bodies, and each one has its own map.
The campus sits inside some taxing districts and outside others
The Village's own FAQ, updated August 25, 2026, makes the point plainly. Taxing-district boundaries in Illinois often don't match village boundaries, and the Village has no say over where other districts draw their lines.
Grayslake is a good example of that mismatch. The Village's FY2025 annual financial report says Grayslake lies across four townships: Avon, Fremont, Lake Villa and Warren. The same report lists Grayslake Community Consolidated School District 46, Woodland CCSD 50, Fremont School District 79 and Grayslake Community High School District 127 among the school districts serving the area.
Fremont School District 79 says the T5 campus "would fall entirely within our school district boundaries." Elementary districts don't overlap, so for the elementary portion of a bill, the campus's taxable value goes to D79. Grayslake addresses in District 46 or Woodland 50 don't share in it.
Here's what public material does and doesn't establish so far.
| Taxing body | Does the campus sit inside it? | What's on the record |
|---|---|---|
| Fremont School District 79 | Yes, entirely | D79 says it has coordinated with Mundelein High School District 120, Grayslake Community High School District 127, financial advisers, legal counsel, legislators and municipal leaders |
| Grayslake CCSD 46 and Woodland CCSD 50 | No, for the elementary portion | Follows from D79's statement that the campus sits entirely within its boundaries |
| Grayslake Community High School District 127 | Partly, per a preliminary briefing | A March 2025 committee briefing put four of the then-proposed 11 buildings inside D127's boundary |
| Mundelein High School District 120 | Not stated | D120 is coordinating with D79; D79's statement doesn't describe how the campus divides between the high school districts |
| Village of Grayslake | Yes | The Village is studying how to use its own share |
| Park, library and fire districts | Not confirmed | No parcel-level statement located |
Treat the District 127 figure with care. It comes from a 2025 description of an earlier plan, and the campus layout has changed since then. That same briefing said D127 would work with its attorney to make sure the buildings are properly assessed.
The Village's FAQ gives the $1.4 billion as one combined figure across all taxing bodies. It calls the estimate preliminary and subject to change during assessment, and says it was calculated using tax rates on 2026 bills. The Village also says discussions with the districts that stand to benefit began in July 2026.
Being inside a district doesn't automatically mean a lower bill
Say an address is inside one of those districts. The next question is what new commercial value does to a homeowner's bill. In Lake County, the answer runs through the Property Tax Extension Limitation Law, often called PTELL or the "tax cap." Lake County has been under it since the 1991 levy year.
The Illinois Department of Revenue explains that PTELL doesn't cap individual bills or individual assessments. It limits how much a district's total tax collection can grow on existing property to a modest inflation-based increase, "plus an additional amount for new construction."
The Lake County Clerk publishes the formula. A capped district's limiting rate is its highest capped extension from the prior three years, multiplied by the inflation increase, divided by the district's total value minus new construction, annexations and recovered TIF value, plus any disconnected property.
Follow one data center building through that formula.
- The year it first appears on the tax rolls. Its value is left out of the denominator, so the rate is set as if the building weren't there. That rate is then applied to the new building too, and the district collects more money in total. Existing owners' share is set the same way it would have been without the building.
- The years after. The building's value is now part of the district's base. The inflation-capped amount can be spread across a larger pool of property, and that's the path by which the homeowner share can shrink.
- Whatever the district decides. A district that needs more than PTELL allows can ask voters for an increase. How much any one bill moves also depends on assessments and on the parts of the levy that sit outside the cap.
Timing matters here as well. The Village expects the campus to be built over the next seven to ten years. Mayor Elizabeth Davies describes it as a demand-driven project built in phases as enterprise customers sign on, with T5 paying its full share as each building comes online. That means step one repeats with each new building. Benefits to homeowners will arrive in stages over years, and when they arrive depends on construction and on decisions each district makes.
The size of the eventual base is still uncertain. The Village's FAQ describes the latest plan as 6.75 million square feet across 11 buildings, about a third less than earlier plans. The Daily Herald describes the approvals as allowing up to 18 buildings and 10.1 million square feet. The first number is the current plan and the second is the approved maximum. The Village's estimate of nearly $100 million a year in combined property tax after year 20 is a forecast, not a promise.
The Village's own share is the part every Grayslake address can watch
The one piece that follows the village line instead of a school map is the Village of Grayslake's own share. Here the Village has described its intentions in writing.
In the October 2026 newsletter, Mayor Davies says the Village doesn't count or spend money until it's received. She says staff are "actively studying property tax relief, reduced municipal fees, and direct rebate structures." The FAQ separately notes that the data centers will pay utility taxes. It says the Village is considering using much of that money to limit what homeowners pay for municipal services and to start annual direct payments to Grayslake households.
The Village has also launched a feasibility study for a Grayslake Community Recreation Center covering scope, design, partnerships and location. A resident survey is planned. The newsletter says a facility of that size would historically have required bonds backed by property taxes. Associate Village Manager Zack Smith told the Daily Herald the survey will ask residents what they'd like in a recreation facility.
All of this is still being studied. Nothing has been adopted. If you're buying, read it as a stated direction from the Village Board, and don't build it into your budget.
What is still unresolved
A lawsuit challenges the project. The Preservation of Community Well-Being Collective and nine Lake County residents filed a civil suit on July 31 asking the court to invalidate the Village's approvals and block further permits. The plaintiffs allege zoning and Open Meetings Act problems. Those are allegations, not findings. The Village has filed a motion to dismiss. A status hearing is set for October 30.
Separately, T5 has indefinitely suspended its application for a wetland permit. No newer status has been reported.
Public communication is ongoing. The Village released a 23-minute video narrated by Mayor Davies and sent postcards pointing residents to the FAQ. In a video released October 5, officials said technical reviews of water use, sound, vibration, traffic and lighting are continuing. Michael Smith of the Lake County Data Center Opposition Coalition, which backs the lawsuit, told the Daily Herald that the outreach came after the approvals rather than during them.
How to read this for a specific address
When you're weighing a particular Grayslake home, these steps turn the headline into something concrete.
- Get the parcel's most recent tax bill and read every taxing-district line on it. The parcel lookup on Lake County's tax portal is a starting point.
- Check the elementary district. If the line reads Fremont School District 79, the campus is inside that district. If it reads District 46 or Woodland 50, the elementary portion won't draw on the campus. CCSD 46 offers a boundary map, but it notes the map is a general guide and should be confirmed with the district.
- Check the high school district for D127 or D120, and keep in mind that the only figure on how the campus divides between them is the preliminary 2025 briefing.
- Follow the Village Board on rebates, fee reductions and the recreation center study. Those are the parts that apply across the village.
None of this is tax advice. A tax professional can model a specific parcel.
Quick answers
Did T5 receive a tax break? The Village says no. It says there were no incentives, abatements or TIF, and that T5 will pay full property taxes from the start.
Is this the first large commercial project on Peterson Road? No. The Village's FAQ cites the 1.4-million-square-foot Medline distribution center in the same corridor, which it says was planned for non-residential use.
When could households see direct payments? No date exists. As of the October 2026 newsletter, rebates are being studied, not scheduled.
The tax lines on a specific address will tell you more about how this campus affects it than any headline number. If you're weighing a home in Grayslake and want help reading its tax bill, district by district, before you write an offer, Team Pimentel is glad to go through it with you in English or Spanish.
