A will-serve letter shows a utility is willing to serve. It doesn't show that power will be there. Capacity a buyer can rely on is set by a load study for the specific load, held by a signed construction agreement with security, and priced by an electric service agreement that fixes the ramp, minimum bill and term. Read every power document in a land deal by where it sits in that sequence, and treat a seller's will-serve as a lead to verify, not proof.
Before you start
- A will-serve letter states intent under tariff and is conditional. It doesn't reserve MW or fix a date.
- A load study for the marketed load, at a named point of service, is the first document worth underwriting.
- Signed construction agreements and posted security are the first commitment that costs someone real money.
- New large-load tariffs bring minimum bills near 80 to 85% of contract demand and terms of 12 to 15 years. Model them before price.
Utilities issue power documents in a fixed order
Every utility uses its own names, yet the sequence for a large load is close to universal. A customer asks. The utility answers informally. Then it studies the specific load, prices the work, asks for money, and signs a contract that sets the ramp and the bill. Energization comes last. Each step costs the customer more and binds the utility a little more.
- Inquiry response or capacity indication: an email or call note saying the area might support a load.
- Will-serve or ability-to-serve letter: a signed statement that the utility intends to serve, subject to conditions.
- Load study or system impact study: an engineering review of this load, at this point of service, on this ramp.
- Facilities study and cost estimate: the substation, line and upgrade scope, with a price and schedule.
- Letter of agreement, construction agreement or engineering agreement, usually with security or a reimbursement obligation.
- Electric service agreement (ESA) under the applicable tariff: contract capacity, ramp, minimum bill, term, exit terms.
- Energization: equipment in service, meter set, and in ERCOT a written approval to energize.
Dominion Energy's public process in Virginia follows that shape. It offers an infrastructure evaluation and preliminary power plan for sites under consideration, plus a will-serve letter if required. A formal project then needs a site plan, a load letter and a load ramp schedule before Dominion develops short-term and long-term power plans and moves into design, right-of-way acquisition, permitting, procurement, regulatory filings and construction.Dominion Energy
The skill in diligence is knowing which rung a document sits on. A seller's data room rarely labels it for you.
Capacity indications and will-serve letters commit to very little
An inquiry response tells you the utility engineer didn't laugh. That's useful for screening and worth nothing for valuation. It is usually unsigned, undated in any formal sense, and based on a desk look at the nearest substation without any study of the load.
The will-serve letter is a step up because someone signs it. Read what it actually says, though. Most letters state that the utility is willing to provide service under its tariff and rules, subject to studies, facilities, agreements and payment. That's close to restating the utility's legal obligation to serve customers in its territory. It is not a reservation of megawatts at a date. Dominion lists the will-serve letter alongside its preliminary evaluation work, ahead of the site plan, load letter and ramp that a formal project requires.Dominion Energy
Check five things on any letter. Is the MW figure named, and does it match the buyer's ultimate load or only phase one? Is a substation or point of service named? Is there a date, and is it an energization date or just the date of the letter? Does it expire? Who signed it, an account manager or someone in transmission or distribution planning? A letter that names no MW, no station and no date is a courtesy. In practice many letters are issued for zoning, financing or permit applications and say so on their face.
Capacity also moves. A letter written eighteen months ago described a queue that has since filled. Paces looked at ERCOT substations with suitable land nearby and found only about 17% showed positive withdrawal capacity, meaning room to add load without worsening existing overloads. A nearby substation is not headroom.Paces
Load studies are the first document a buyer can underwrite
A load study models this load at this location. It tells you whether the existing system can carry it, which upgrades are needed, and roughly when. Utilities now charge for it and gate it behind site control, which is exactly why a completed study means something.
AEP Ohio's process is a clear public example. Data center requests of 25 MW or more go through PowerClerk, and the customer must control the property and state the location, load ramp and final load. The study fee is $10,000 for loads above 25 MW and under 50 MW, $50,000 for 50 MW to under 100 MW, and $100,000 at 100 MW and above. Unpaid fees mean the request is treated as withdrawn. AEP targets completion in 45 days, or 60 days when regional transmission upgrades are needed. As of November 2026 AEP is running studies in tranches, and its second 2026 tranche closed to applications on September 30, 2026.AEP Ohio
Texas raised the bar further. In September 2026 the Public Utility Commission of Texas adopted interconnection rules for large loads under Senate Bill 6, setting a flat $100,000 study fee for every large load customer and dropping a proposed non-refundable fee of $50,000 per MW. If a customer misses its energization schedule by 24 months, the utility applies the customer's financial security to amounts owed and returns the balance. Utility Dive reported the rules were adopted during a pause on new data center interconnections meant to allow an audit of ERCOT's roughly 474 GW queue, about 90% of it data centers.Utility Dive
The Berkeley Lab and Brattle review of 55 large-load tariffs found that explicit study requirements, usually paid by the customer, are moderately common and increasing in tariffs proposed since 2025. Examples include development deposits that the utility draws down and refunds if unused.Lawrence Berkeley National Laboratory and The Brattle Group
What a study does not do is hold capacity. It reflects the queue on the day it ran. Ask for the study date, the assumed ramp, the list of required upgrades, and whether the utility will honor the result if the contracts are signed within a set window. A study for 100 MW doesn't support a 300 MW campus plan.
Construction agreements and security are the first real commitment
The facilities study turns the load study into a scope and a price: the new substation or bay, the line extension, transmission upgrades, and who pays for each. The utility will not order a transformer on a promise. Before it spends, it wants a signed agreement with money behind it.
AEP Ohio presents two contracts after the study. The Letter of Agreement makes the customer reimburse 100% of buildout costs if it cancels or delays the project more than 12 months before the target energization date, an obligation that ends when the project is complete. The ESA carries a good-faith energization estimate. Both must be signed within 60 days or the customer loses its place.AEP Ohio
Collateral is where tariffs now bite. AEP Ohio requires a guarantee or collateral equal to 50% of total minimum charges over the full term, due at signing, with an exemption only for customers rated at least A- by S&P and A3 by Moody's with large cash balances. Surety bonds aren't accepted. Dominion's GS-5 schedule requires collateral of $1.5 million per MW of contracted capacity.AEP OhioLawrence Berkeley National Laboratory and The Brattle GroupUtility Dive
For a land buyer this rung matters most. Signed construction agreements and posted security mean someone with a balance sheet decided the site was worth real dollars. Ask who posted it, though. If the security belongs to a prior developer, it may not move with the land.
The ESA sets the ramp, the minimum bill and the way out
The electric service agreement is the contract that governs the bill for a decade or more. Under the new large-load tariffs it fixes contract capacity, the ramp schedule, the minimum billing demand, the term, collateral and the exit fee. A buyer reading an ESA should model the minimum bill as a fixed cost, because that's what it is.
| Utility and tariff | Threshold | Minimum billing | Term and ramp | Exit or early termination |
|---|---|---|---|---|
| AEP Ohio, Schedule DCT (effective July 23, 2025) | 25 MW | Minimum demand up to 85% of contract capacity | Ramp of up to four years at 50%, 65%, 80%, 90% of capacity, plus eight years | After year five post-ramp, exit fee of 36 months of minimum charges |
| Dominion Virginia, GS-5 (effective January 1, 2027) | 25 MW | 85% of contracted transmission and distribution demand, 60% of generation | 14-year minimum, four-year ramp with at least 20% of capacity per year | Collateral of $1.5 million per MW of contracted capacity |
| Georgia Power, PSC rule of January 2025 | Over 100 MW | Minimum billing requirements allowed | Contracts up to 15 years, up from 5 | Each contract filed with the PSC for review |
| 55 tariffs reviewed by LBNL and Brattle | Mostly 5 to 100 MW | Median minimum billing demand of 80% of contract demand | Median minimum term of 12 years for tariffs proposed since 2025, up from 5 | Exit fees increasingly common, often a multiple of the minimum monthly charge |
Read the ramp closely. AEP's tariff sets minimum contract capacity at 50% in year one, rising to 90% in year four, and the contract term starts at actual energization. Dominion's GS-5 requires the load to ramp at least 20% of contracted capacity a year. Staged service also shows up in the utility's plan itself. Dominion describes serving load in stages as a bridge while the final power plan is built, so a 300 MW ESA may deliver a fraction of that on day one.AEP OhioLawrence Berkeley National Laboratory and The Brattle GroupDominion Energy
Georgia's rule lets Georgia Power bill customers above 100 MW for upstream generation, transmission and distribution costs as construction progresses, and requires every such contract to go to the PSC for review. For a Georgia site, ask whether the contract has been filed and where the review stands.Georgia Public Service Commission
Utility Dive counted 264 large-load tariff filings in Halcyon's tracker by mid-August 2026. The terms above will keep moving. Check the tariff in force on the day you sign, not the one quoted in last year's deck.Utility Dive
What each document proves and what it does not
Use this when a data room arrives. Put every power document on a row before anyone discusses price.
| Document | What it proves | What it does not prove | Red flags |
|---|---|---|---|
| Inquiry response or capacity indication | The utility has engaged and sees no obvious bar | Any MW, date or cost | Forwarded email with no sender title, no station named |
| Will-serve or ability-to-serve letter | Intent to serve under tariff, subject to conditions | Reserved capacity, an energization date, upgrade cost | No MW, no expiry, signed by sales staff, written for a different load or owner |
| Load study or system impact study | This load at this point of service was modeled, with upgrades listed | That capacity is held, or that the ramp works for a larger campus | Study older than a year, MW below the marketed figure, utility no longer honoring results |
| Facilities study and cost estimate | Scope, rough cost and schedule of the utility work | That anyone has agreed to pay | Estimate expired, long-lead equipment not ordered, rights of way unresolved |
| Letter of agreement or construction agreement with security | A party has put money at risk and the utility is spending | Final service terms or the bill | Security posted by a party that is leaving the deal |
| Electric service agreement | Contract capacity, ramp, minimum bill, term, exit terms | That the substation will be done on the estimated date | Not assignable, minimum bill not modeled, regulatory review pending |
| Energized and metered service | Power flows today at a known capacity | That expansion capacity exists | Meter capacity far below the marketed MW |
Sites from our inventory that show the point
Two sites in our inventory show why the document matters more than the headline MW.
| Region | Power evidence | Land | Where it stands |
|---|---|---|---|
| West-central Ohio | Dual 345 kV lines on site. A 400 MW utility load study was resubmitted, with results expected around the end of 2026. 350 MW of on-site gas is committed. | About 514 acres | Watch list. The study result is the document that moves it from a named path to a documented one. |
| Southwest Pennsylvania | The only executed agreement is a 17.5 MW distribution interconnection left from a solar project's export. Marketing describes a 600 MW tap on a 345 kV line. | About 116 acres | Watch list. The signed paper covers export at 17.5 MW, not 600 MW of load. A load study would settle it. |
In both cases the seller's figure is real as an intention. The executed paper is far smaller, or not issued yet. Locations, owners and documents are shared on a call.
How to read a seller's will-serve letter in a land deal
A listing that says "450 MW available, will-serve in hand" is making a claim about power, not land. Map it to an evidence ladder. Rung 0 is a map with nothing behind it. Rung 1 is proximity to a line or substation of the right voltage. Rung 2 is a named MW figure at a named station from a utility or planning record, or an existing large connection such as a retired plant's export or an energized load. Rung 3 is a utility study or approval for this load: a load study, a facilities study, security posted. Rung 4 is an executed service or interconnection agreement with a date, or service energized and metered.
Most seller will-serve letters land on rung 2 at best. They become rung 3 only when a study for the marketed load sits behind them.
- Ask for the letter itself, not a summary. Read the conditions paragraph first.
- Match the MW, the point of service and the customer name to the deal. A letter issued to a prior developer for 60 MW says little about a 400 MW campus.
- Find the date and any expiry. Old letters describe old queues.
- Ask whether a load study was requested, paid for and completed, and get a copy.
- Ask whether the letter, study position or security is assignable to a buyer, and get the utility to confirm in writing.
- Call the utility's large-load or economic development team with the seller's permission and confirm the request is still active.
- Model the applicable large-load tariff's minimum bill, term and collateral before agreeing on price.
Then sort the site. Tier A has documented power, rung 3 or 4. Tier B has a named power path with a date, usually a current utility letter tied to a study in progress. Tier C is land near capacity and should be priced as land. Kill disqualifiers before any of this: the site already claimed or operating, under option, listed widely, owned by an environmental-liability buyer, carrying coal ash or contamination, or sitting in a county with a moratorium.
Energization is its own gate. In ERCOT, since October 2025, any load studied as a large load needs written approval from ERCOT's Large Load Integration team before the utility may energize it. A signed ESA doesn't replace that step.ERCOT
Invariant screens sites this way before any introduction. The power documents get read and placed on the ladder first, and the parcel comes second.
Questions that come up.
Is a utility will-serve letter a guarantee of power for a data center?
No. A will-serve letter usually states the utility's intent to serve under its tariff, subject to studies, facilities, agreements and payment. It does not reserve megawatts or fix an energization date. Capacity is set by a load study and held by signed agreements with security.Dominion EnergyAEP Ohio
What is the difference between a load study and a facilities study?
A load study tests whether the system can carry a specific load at a specific point and lists the upgrades needed. A facilities study turns that into a detailed scope, cost estimate and schedule for the utility work. Many utilities fold both into one study for distribution-level loads.
How much does a utility load study cost for a data center?
It depends on the utility. AEP Ohio charges $10,000 to $100,000 depending on load size, starting above 25 MW. Texas set a flat $100,000 study fee for large loads in ERCOT in September 2026, with financial security posted separately.AEP OhioUtility Dive
What is a minimum bill in a data center electric service agreement?
It is the amount the customer owes each month regardless of actual use, usually tied to a share of contract demand. The Berkeley Lab and Brattle review found a median minimum billing demand of 80% of contract demand. AEP Ohio's data center tariff sets it at up to 85% of contract capacity.Lawrence Berkeley National Laboratory and The Brattle GroupAEP Ohio
Can a will-serve letter be transferred when the land is sold?
Only if the utility agrees. Letters, study positions and security are usually tied to the requesting customer and load. Get written confirmation from the utility that it will honor them for the buyer before you rely on them in price.
How does Invariant check a site's power documents?
Invariant places every power document on an evidence ladder, from map proximity up to an executed agreement or metered service, and confirms with the utility where possible. Sites are tiered by that evidence before any parcel work or introduction.
Sources and references.
Primary sources checked for this guide on . The location, equipment, and operating plan determine which requirements apply to a project.
- AEP OhioData Center Tariff (Schedule DCT) ↗
- Dominion EnergyData Center Requests ↗
- Lawrence Berkeley National Laboratory and The Brattle GroupElectricity Rate Designs for Large Loads: Evolving Practices and Opportunities, 2026 Update ↗
- Utility DiveLarge load tariffs are getting longer and stricter, LBNL and Brattle find ↗
- Annandale TodayNew utility rate class approved for data centers ↗
- Georgia Public Service CommissionPSC Approves Rule to Allow New Power Usage Terms for Data Centers ↗
- Utility DiveTexas PUC adopts data center interconnection rules ↗
- ERCOTMarket Notice M-B100825-01: Approval to Energize process for Large Loads ↗
- PacesGrid planning, data centers and transmission investment ↗