MISO Wants PMUs on Data Centers and a Separate Rulebook for Loads With 25 MW of Servers
- Data Centers FERC & Federal Policy & Markets Regulatory
Marin Holt
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- 8 minutes read
- Large load threshold: 50 MW
- Computational load threshold: 25 MW
- Requested effective date: 4 December
- RTOs under FERC show-cause order: six
MISO asked federal regulators on 28 August 2026 to set new connection rules for any load above 50 MW. The Midcontinent Independent System Operator wants ramp limits, ride-through duties and synchrophasor monitoring on those sites. It runs the grid and wholesale markets across 15 states, from Louisiana to Minnesota. The filing at the Federal Energy Regulatory Commission requests a 4 December effective date. It also creates a class of customer no US grid operator had defined before: the computational load.
MISO defines a large load as a single site that draws more than 50 MW. A computational load is a large load carrying at least 25 MW of demand from information technology equipment, meaning servers, storage and networking hardware. Under the proposal a 60 MW data center and a 60 MW steel mill would answer to different rules.
The filing answers show-cause orders FERC issued in June under section 206 of the Federal Power Act. The Commission sent one to each of the six regional grid operators it oversees. Each had 60 days to defend its existing tariff or rewrite it, against five named categories of reform. ERCOT and PJM moved first. MISO says it will file more proposals by 16 November.
Four requirements, and one that is new
The framework covers four areas. Visibility rules require transmission customers to hand MISO modeling data for each facility. They must also supply real-time and day-ahead forecasts. Ramp rules cap how fast a computational load may raise or lower its draw during steady-state transitions.
Ride-through rules set minimum performance during voltage and frequency disturbances, so a plant does not drop off the system or cut its own demand during an event.
The fourth is the one to watch. MISO wants phasor measurement units on computational loads. PMUs give it high-resolution, time-synchronized data on how a private customer behaves during a disturbance. PMUs are standard instrumentation on generators. Pointing them at a customer meter treats a data center as a machine the operator must model, not as a bill to send.
MISO told FERC that computational loads “may exhibit rapid and coordinated changes in demand, significant power-electronic behavior, and distinct responses to transmission system disturbances.” That sentence is the whole case for the filing.
The numbers behind the filing
MISO told regulators that demand across its footprint grew about 0.5% a year between 2009 and 2024. It now expects 1% to 2% a year through 2044, with the faster rates arriving first. The rules are written for the front of that curve.
Why It Matters
The proposal grandfathers existing and nearly complete commercial arrangements. That clause is where the fight will happen. The incidents that built the case for these rules came from data centers already energized and already tripping, not from the sites still waiting in the queue. A rule that binds the next site and exempts the last one leaves the measured problem in place. It also prices the fix into projects that have not yet caused it.
Developers inside MISO should read the 25 MW IT-equipment line before the 50 MW headline. The lower number decides which rulebook applies. A campus that lands just over it inherits PMU installation, ramp discipline and ride-through duties. A comparable industrial load of the same size carries none of them.
MISO has not yet filed its cost-shift protections or its rules for generation sited next to large loads. Both land by 16 November. Both matter more to a project pro forma than anything in this filing.
Critical Perspective
The computational load test is the weak joint in this framework. MISO proposes to classify a site by how much of its demand comes from information technology equipment, at a threshold of 25 MW. MISO does not meter servers. It meters the point of interconnection. The classification therefore rests on what a customer declares about equipment behind its own fence, and the published account of the filing does not describe how MISO would audit that number.
The reporting on the filing also carries no numbers for the requirements themselves. No ramp rate in megawatts per minute appears, and no voltage or frequency curve a plant must ride through. Those values decide what the rules cost to meet. MISO asked for a 4 December effective date, which leaves developers pricing an obligation whose size is not yet public.
A third problem sits outside the filing. ERCOT and PJM wrote their own versions first, and MISO is writing a third. A developer choosing between footprints now compares rulebooks as well as queue times. Reliability rules that differ by region reward the most permissive region, which is the opposite of what a fleet-wide reliability problem calls for.
Sources
- Utility Dive: Large loads face reliability requirements under MISO proposal
- FERC: Launches Aggressive Targeted Action to Speed Large Load Integration
- MISO: Large Load Interconnection Reliability Requirements
