MISO's June 1 Planning Year and Seasonal Capacity: When to Renew an Ameren-Territory Contract

MISO June 1 vs PJM June 1 in one state

Illinois cultivators split across two ISOs. ComEd customers sit in PJM with a single capacity delivery year starting June 1. Ameren Illinois customers sit in MISO with a planning year that also turns June 1 but uses the planning resource auction (PRA) seasonal clearing prices [miso-pra-2026].

A Springfield craft grow and a Chicago cultivation center both shop retail electric choice through ICC-certified suppliers, but capacity math on the bill is not interchangeable.

What the 2026/2027 MISO auction cleared

MISO's 2026/2027 planning resource auction procured sufficient capacity for the planning year beginning June 1, 2026 [miso-pra-2026]. Market summaries report summer capacity near $424.30 per MW-day in key zones, down from the prior year's spike but still far above 2024 levels [enel-miso-capacity-2026] [cub-ameren-spike].

MISO also clears seasonal and annual products differently. Suppliers may pass summer capacity at the higher seasonal rate and winter at lower blended rates. Your contract language determines which product you pay for.

ISO	Auction	Typical grow impact
MISO (Ameren)	PRA seasonal + annual	Summer PLC drives spike
PJM (ComEd)	RPM annual	Single PLC year-round

See our June 1 Mid-Atlantic calendar for PJM comparison.

Why Citizens Utility Board flagged Ameren spikes

CUB's June 2026 Q&A explained that downstate Illinois customers saw electricity price spikes tied to MISO capacity costs remaining elevated versus 2024 even as the 2026/2027 auction declined from 2025/2026 [cub-ameren-spike]. Cultivation facilities with high summer PLC amplify the dollar impact.

Ameren industrial average rate was 10.65 cents/kWh in June 2026 [eia-epm-5-6-a], lower than ComEd commercial averages, but demand-metered grows rarely pay the EIA average.

Renewal timeline for Ameren territory

April 1: Export interval data from prior June through August. Identify PLC-setting interval.

April 15: Request renewals with explicit MISO capacity pass-through formula. Ask which local resource zone applies.

May 15: Compare fixed offers to Ameren price to compare on your delivery class [il-plugin-illinois].

June 1: Planning year begins; verify pass-through on first bill.

July through September: Protect PLC during heat and humidity. Dehumidification plus lighting sets peaks.

Before evergreen deadline: Confirm auto-renewal date (see evergreen clause article).

Worked example: Peoria-area indoor grow

Assume 160 kW PLC, summer capacity pass-through at $424.30/MW-day [enel-miso-capacity-2026]:

• Simplified monthly capacity cost ≈ 160 kW × ($424.30/1000) × 365/12 ≈ $2,065/month in summer-weighted billing (actual rules vary by supplier tariff)

Cut PLC to 120 kW through stagger:

• ≈ $1,549/month

≈ $516/month savings from operations, independent of LED retrofit kWh savings.

Add DS-3 or DS-4 distribution demand on Ameren delivery schedules.

Contract clauses to read on MISO deals

• Seasonal capacity product definition (summer-only vs annual blend)
• PLC update frequency (annual vs monthly true-up)
• Pass-through change of law for MISO tariff amendments
• Bandwidth if canopy expansion adds 30 percent load mid-contract

Fixed energy at 7.5 cents/kWh means little if capacity pass-through adds 4 cents/kWh equivalent in summer.

ComEd sites in the same company

MSOs with both Ameren and ComEd meters should run separate RFPs. Aggregating volume may help energy price but blurs ISO-specific capacity risk. At minimum, align June 1 review meetings for both territories.

ComEd vs Ameren: do not share one RFP template

Corporate procurement teams sometimes issue one Illinois RFP. ComEd meters need PJM capacity language at $329.17/MW-day for 2026/2027 [enel-pjm-capacity-2026 context in sibling articles]. Ameren meters need MISO seasonal PRA products [miso-pra-2026] [enel-miso-capacity-2026].

A supplier winning ComEd volume may still misprice Ameren if their pass-through desk treats both as PJM.

IPA, PEA, and supplier choice on Ameren default

Ameren default supply reflects Illinois Power Agency procurements [il-plugin-illinois]. Customers on alternative retail electric suppliers avoid ComEd-style Purchased Electricity Adjustment on ComEd; Ameren default has its own true-up mechanics [il-plugin-illinois]. Shoppers compare supplier fixed offers to the price to compare printed on the Ameren bill for the delivery class.

CUB's June 2026 piece on downstate spikes explains why default rose even when auction cleared lower than 2025/2026 [cub-ameren-spike].

Seasonal capacity products explained simply

MISO's planning resource auction clears seasonal capacity for summer peaks and annual products for broader obligations [miso-pra-2026]. Your supplier contract may bill:

• Summer capacity at higher $/MW-day
• Winter at lower blended rate

Ask for a line-item example bill using your PLC before signing. Fixed vs index guide covers pass-through vocabulary.

Downstate cultivation footprint growth

Illinois craft growers and outdoor hybrid greenhouses cluster in central Illinois Ameren territory. Expansion from 5,000 to 12,000 sq ft canopy changes bandwidth on supply contracts signed at lower load [il-plugin-illinois].

Renew in April with engineer-stamped load letter if expansion energizes before June.

Demand ratchets on Ameren delivery

Ameren delivery schedules DS-3 and DS-4 bill distribution demand per kW [state data]. Supply savings do not reduce delivery ratchets. Pair MISO capacity management with peak demand management.

Extended checklist for June 1 MISO year

1. Confirm MISO zone on supplier contract (Local Resource Zone)
2. Pull June-August interval CSV from Ameren portal
3. Model PLC at current vs staggered schedule
4. Compare renewal to Illinois commercial rates [eia-epm-5-6-a]
5. Calendar evergreen notice on same spreadsheet as June 1
6. If multi-site includes ComEd, run separate June 1 PJM calendar

Historical context: why CUB still warns downstate customers

Even when MISO auction clearing prices decline year over year, prior under-recovery and seasonal summer tags can keep customer bills elevated [cub-ameren-spike]. Treat auction headlines and bill impact as separate facts.

Linking retrofit to MISO tag

LED retrofits that shrink August peak can lower next planning year PLC if stagger holds [enel-miso-capacity-2026]. Send supplier updated load letter after retrofit commissioning.

When to call the supplier before June

If April interval data shows a PLC 20 percent below last year, phone the supplier account manager before the May renewal letter arrives. Proactive PLC updates occasionally reduce pass-through on renewal quotes [enel-miso-capacity-2026]. Waiting until June bill posts loses a negotiation window.

MISO's June 1 planning year is the downstate Illinois cultivator's capacity New Year. Renew with fresh PLC data before summer sets next year's tag. File the renewal spreadsheet alongside your ICC supplier choice disclosure so the same numbers appear in compliance, finance, and operations reviews [il-plugin-illinois]. If CUB publishes another downstate price Q&A in June, read it for context on how auction results translated to bills [cub-ameren-spike], then adjust your forecast rather than copying last year's budget line.

Why ComEd and Ameren contracts need different fine print

Corporate teams sometimes issue one Illinois RFP. That fails on capacity language. ComEd meters sit in PJM with one annual capacity delivery year. Ameren meters sit in MISO with seasonal planning resource auction products [miso-pra-2026]. A supplier who wins Chicago volume may still misprice downstate if their pass-through desk treats both ISOs identically.

MISO's 2026/2027 auction procured sufficient capacity for the planning year beginning June 1, 2026 [miso-pra-2026]. Market summaries report summer capacity near $424.30 per MW-day in key local resource zones, with lower annualized values in the $116 to $126 per MW-day range depending on zone and seasonality [enel-miso-capacity-2026]. Your contract should state which product you pay: summer-only seasonal capacity or an annual blend.

CUB's June 2026 Q&A explained that downstate customers saw electricity price spikes tied to MISO capacity costs remaining elevated versus 2024 even as the 2026/2027 auction declined from 2025/2026 [cub-ameren-spike]. Auction headlines and bill impact are separate facts. Prior under-recovery can keep customer rates high even when clearing prices fall.

Question for supplier	Why it matters
Which Local Resource Zone?	Cleared price varies [enel-miso-capacity-2026]
Summer vs annual capacity product?	Dollar pass-through differs by season [miso-pra-2026]
How often is PLC updated?	Stagger gains may lag until true-up
Bandwidth if canopy expands?	Craft grows scaling in central IL [il-plugin-illinois]

Ameren industrial average rate was 10.65 cents/kWh in June 2026 [eia-epm-5-6-a]. Demand-metered cultivators rarely pay that average once delivery kW charges spread over cultivation load factor. Downstate greenhouse operators with supplemental winter lighting should include those kWh in April supplier forecasts so MISO capacity pass-through quotes reflect full seasonal load [miso-pra-2026].

Illinois Power Agency procurements feed Ameren default supply benchmarks shoppers compare against supplier offers [il-plugin-illinois]. Customers on alternative retail electric suppliers avoid ComEd-style Purchased Electricity Adjustment mechanics on ComEd; Ameren default has its own true-up paths [il-plugin-illinois]. When CUB warns downstate customers about summer spikes, read the piece for bill translation context even if auction clearing prices declined year over year [cub-ameren-spike].

If April interval data shows PLC twenty percent below last year, call the supplier before the May renewal letter arrives. Proactive PLC updates occasionally reduce pass-through on renewal quotes [enel-miso-capacity-2026]. LED retrofits that shrink August peak can lower next planning year PLC if stagger holds through verification interval [enel-miso-capacity-2026]. Send supplier an updated load letter after retrofit commissioning. Calendar evergreen notice on the same spreadsheet as June 1 so auto-renewal does not bypass your April RFP [il-plugin-illinois].