Are IRNUS Charges Refundable? What CAISO Participants Need to Know

If you've encountered a line item labeled IRNUS on a CAISO settlement statement and you're wondering whether it can be refunded, disputed, or reversed — you're not alone. These charges sit at the intersection of energy market operations and software-driven settlement systems, which makes them confusing even for experienced market participants.

This article breaks down what IRNUS charges are, how the refund and dispute process works within CAISO's settlement framework, and which factors determine whether a specific charge is recoverable.

What Is an IRNUS Charge in CAISO?

IRNUS stands for Intra-Regional Net Uninstructed Supply. It is a charge applied within the California Independent System Operator (CAISO) energy market when a resource produces or schedules energy beyond what it was instructed to deliver — without explicit dispatch authorization.

In simpler terms: if a generator or scheduling coordinator supplies more energy than CAISO told it to, the system flags the excess. That excess is categorized as uninstructed deviation, and IRNUS is the mechanism through which the market accounts for — and financially penalizes — that deviation.

CAISO's settlement software calculates these charges automatically based on real-time telemetry, dispatch instructions, and metered output. The process is highly automated, which means errors can and do occur, but so can legitimate charges from actual deviations.

Are IRNUS Charges Refundable?

Yes — under specific conditions. IRNUS charges are not automatically non-refundable, but they are also not automatically reversed. Whether a charge is recoverable depends on the nature of the deviation, the accuracy of the underlying data, and whether the dispute is filed correctly and on time.

There are generally two paths through which IRNUS charges can be addressed:

1. Settlement Dispute Process

CAISO operates a formal settlement dispute window. Market participants have a defined period — typically tied to the settlement cycle — during which they can flag charges they believe are incorrect. This is the most common route for recovering IRNUS charges that resulted from:

• Meter data errors — incorrect metering can cause CAISO's settlement system to record a deviation that didn't actually occur
• Telemetry failures — if real-time data wasn't transmitting correctly, the system may have misread the resource's output
• Dispatch instruction miscommunication — discrepancies between what was logged as the instruction and what was actually communicated
• Software calculation errors — rare, but CAISO's settlement systems have occasionally required recalculation runs

Filing a dispute requires supporting documentation: meter data, dispatch logs, SCADA records, and communications with the CAISO operations desk if applicable.

2. CAISO Recalculation Settlements

CAISO runs multiple settlement iterations — Initial Settlement, Recalculation Settlement 1 (T+12M), and Recalculation Settlement 2 (T+24M). Some IRNUS charges that appear incorrect in initial settlement are naturally corrected in a recalculation run as more accurate data becomes available. Participants don't always need to file a dispute — sometimes the correction is automatic.

However, relying on recalculations without monitoring your statements is risky. If the underlying data error isn't caught, it may persist through all settlement iterations.

Key Variables That Determine Whether a Charge Is Recoverable 🔍

Not every IRNUS charge is recoverable, and the outcome depends heavily on several factors:

Variable energy resources like solar and wind are subject to specific uninstructed deviation rules that acknowledge their inherent output variability. The thresholds and charge calculations for these resources are different from those applied to thermal or storage assets — which means the same megawatt deviation can carry very different financial consequences depending on resource classification.

What the Dispute Process Actually Involves

Filing a successful IRNUS dispute isn't just submitting a ticket. It typically requires:

• Pulling interval meter data from your metering system and comparing it against CAISO's settlement records
• Cross-referencing dispatch instructions from the CAISO portal against your internal operations logs
• Identifying the specific settlement intervals where the discrepancy occurred
• Preparing a written dispute submission through CAISO's Market Participant Portal with supporting attachments

Most scheduling coordinators manage this process through dedicated settlement analysts or software tools that flag deviations automatically. Smaller participants without dedicated staff often find the process more difficult to navigate — not because the rules are unfair, but because the documentation requirements are detailed and the timelines are firm.

When IRNUS Charges Are Not Refundable

Some IRNUS charges are legitimate and will not be reversed regardless of how well a dispute is filed. If your resource genuinely deviated from its dispatch instruction — and the meter data, telemetry, and CAISO records all agree — the charge stands. These charges exist specifically to maintain grid reliability and create financial incentives for resources to follow dispatch instructions accurately.

It's worth distinguishing between wanting a charge reversed and having a valid basis to dispute it. The CAISO process is designed to correct data errors and calculation mistakes — not to waive charges for actual uninstructed deviations. 🗂️

The Gap That Determines Your Outcome

Whether an IRNUS charge is refundable in your case comes down to details that no general article can assess from the outside: the accuracy of your meter data, the state of your telemetry at the time of the deviation, which settlement iteration you're in, and whether you have the documentation to support a dispute. Those factors vary significantly across resource types, market participants, and individual settlement periods — and they're what makes each situation meaningfully different from the next. ⚡