MISO 2026/27 PRA: $424 Summer and $116 Annualized Capacity Explained

What MISO's Planning Resource Auction does

MISO's Planning Resource Auction (PRA) procures accredited capacity for the planning year from June 2026 through May 2027 [miso-2026-pra-release]. Unlike PJM's single annual RPM clearing price for the whole delivery year, MISO clears seasonal prices: summer, fall, winter, and spring [miso-2026-pra-release]. Load Serving Entities must cover obligations in each season; the annualized number is a blended view suppliers use when quoting all-in rates.

MISO reported the 2026 PRA cleared 3.5 percentage points above the summer Planning Reserve Margin target of 7.9% [miso-2026-pra-release]. Capacity offered grew about 4% per season versus the prior auction, driven by new solar, gas, and storage [utility-dive-miso-2026].

The 2026/27 clearing prices by season

MISO published these Auction Clearing Prices [miso-2026-pra-release]:

Season	LRZ 1-7 (North/Central)	LRZ 8 & 10	LRZ 9
Summer (Jun-Aug)	$424.30/MW-day	$384.10/MW-day	$412.10/MW-day
Fall (Sep-Nov)	$33.92/MW-day	(zone-specific)	(zone-specific)
Winter (Dec-Feb)	$35.97/MW-day
Spring (Mar-May)	$7.61/MW-day
Annualized	$126.19/MW-day	$116.06/MW-day	$123.12/MW-day

Summer dominates the cost story. A cultivator whose supplier bills MISO capacity seasonally will see the highest adder during June through August when HVAC and dehumidification already spike kWh.

Why Ameren Illinois growers noticed June 1

Downstate Illinois is Ameren territory in MISO, not ComEd's PJM footprint. CUB explained Ameren supply price spikes in 2026 partly through MISO capacity costs embedded in default supply [cub-ameren-2026]. The $424.30 summer clearing price is down from the prior year's record near $666/MW-day [utility-dive-miso-2026] but still roughly fourteen times some 2024 levels cited in consumer advocacy materials [cub-ameren-2026].

If you operate cultivation in Springfield, Peoria, or other Ameren zones, your June 2026 supply reset reflects MISO PRA, not the PJM $329/MW-day figure Chicago operators discuss.

Worked example: summer capacity on a downstate grow

Assume a 500 kW peak facility in LRZ 1-7 with 1.8 million kWh annual use.

Summer capacity cost (illustrative): 0.5 MW × $424.30/MW-day × 92 summer days ≈ $19,518

If smoothed across all kWh: $19,518 ÷ 1,800,000 kWh ≈ 1.1 ¢/kWh for summer months only

Suppliers rarely bill that simply. Many use annualized $126.19/MW-day ($46,059/MW-year) spread across twelve months [miso-2026-pra-release]:

0.5 MW × $46,059 ≈ $23,030 per year ≈ 1.3 ¢/kWh at 1.8 million kWh

Compare to PJM's $120,147/MW-year cap for the same 0.5 MW: about $60,074 per year or 3.3 ¢/kWh at the same consumption. MISO annualized is lower than PJM's cap, but summer seasonal exposure can concentrate costs in June through August when your facility already runs hardest.

Reliability-Based Demand Curve effects

This is the second year MISO used a Reliability-Based Demand Curve (RBDC) [miso-2026-pra-release]. RBDC lifts clearing prices as reserves tighten toward minimum requirements rather than flat pricing at surplus. Enel and Utility Dive both noted the curve kept summer prices elevated even as new solar added supply [enel-miso-2026-27] [utility-dive-miso-2026].

For operators, RBDC means capacity prices can jump quickly when load growth outruns accredited supply even if nameplate megawatts on the system rise. Michigan and Illinois load forecasts include industrial and data center growth similar to PJM trends.

Michigan cultivators on MISO

Michigan commercial customers in MISO zones (portions of Consumers Energy and Indiana Michigan Power territory) see PRA through default supply or supplier pass-through. Michigan's capped electric choice program limits shopping options; many grows remain on utility default where PRA is fully embedded.

If you are in the choice queue, specify whether a supplier quote uses annualized or seasonal MISO capacity settlement. A quote that averages $126/MW-day may understate summer cash flow needs.

Contract timing around June 1

MISO's planning year aligns with PJM's June 1 start, which makes mid-May through early June a busy renewal window across the Midwest [enel-miso-2026-27]. Actions:

Match contract start to June 1 when possible so capacity seasons align with supplier assignments.

Request seasonal breakout on supplier proposals. If they only show an annual average, ask for summer-month dollars explicitly.

Compare Illinois sites on ComEd versus Ameren if you are expanding. Same state, different RTO, different capacity mechanics.

Plan efficiency before renewal. RBDC rewards accredited capacity; reducing your PLC through peak management lowers obligation megawatts even when price is high.

Fall and spring: do not ignore the low seasons

Spring cleared at $7.61/MW-day in LRZ 1-7 [miso-2026-pra-release]. Operators sometimes assume capacity is "only a summer problem." MISO still charges seasonal obligations in fall and winter, just at lower clearing prices. Your supplier may true-up if they front-loaded summer costs into a flat monthly adder.

Understanding the seasonal stack helps you reconcile a confusing true-up invoice in October or March. Ask your supplier which MISO season each monthly adjustment references.

Worked example: Ameren Illinois default vs fixed supply

Assume a 350 kW peak, 1.4 million kWh annual indoor grow in Ameren Illinois territory on default supply that embeds MISO capacity pass-through.

Input	Value
Annual kWh	1,400,000
Summer peak share of annual kWh	42% (June through August)
MISO summer capacity adder (modeled)	0.5 MW obligation × $424.30/MW-day × 92 days ≈ $19,518
Annualized capacity adder (same obligation)	≈ $23,030 spread across 12 months

If a retail supplier quotes 7.8 cents per kWh all-in fixed for 24 months, compare against default by isolating the capacity line on three consecutive summer bills rather than dividing annual dollars by total kWh. A fixed quote that hides seasonal MISO true-ups can look cheaper in April and expensive in July.

Staggering two flower rooms so peak drops from 350 kW to 290 kW lowers the obligation megawatts before the June 1 planning year assignment. That operational change affects both default pass-through and supplier quotes tied to PLC tags.

LRZ 8, 9, and 10: why two Illinois neighbors can see different annualized clears

MISO published distinct summer and annualized clearing prices for Local Resource Zones 8, 9, and 10 versus LRZ 1-7 [miso-2026-pra-release]. Summer in LRZ 1-7 cleared at $424.30/MW-day while LRZ 8 and 10 cleared at $384.10/MW-day and LRZ 9 at $412.10/MW-day [miso-2026-pra-release]. Annualized blends landed at $126.19 (LRZ 1-7), $116.06 (LRZ 8 and 10), and $123.12 (LRZ 9) [miso-2026-pra-release].

Ameren Illinois cultivators should confirm LRZ on the supplier contract, not only the utility name. A grow near the MISO/PJM seam still in Ameren territory uses MISO PRA mechanics, not ComEd's PJM RPM cap [cub-ameren-2026]. Michigan sites on Consumers Energy or Indiana Michigan Power in MISO see the same auction with zone-specific annualized prices [enel-miso-2026-27].

Worked comparison at 0.45 MW obligation:

Zone group	Annualized $/MW-day	Annual capacity cost	At 1.6M kWh/yr
LRZ 1-7	$126.19 [miso-2026-pra-release]	≈ $20,721	≈ 1.29 ¢/kWh
LRZ 8/10	$116.06 [miso-2026-pra-release]	≈ $19,058	≈ 1.19 ¢/kWh

The spread is real but smaller than the summer seasonal spike. A supplier smoothing annualized $126/MW-day across twelve months may understate July cash needs when summer clearing is $424/MW-day [miso-2026-pra-release]. Ask for a month-by-month capacity schedule in writing.

Utility Dive noted new solar and gas pushed offered capacity up about 4% per season while RBDC still kept summer prices elevated [utility-dive-miso-2026]. Cultivators planning 2027/28 efficiency should target summer peak hours: lowering obligation MW before next April's PRA matters more than shaving winter kWh for capacity cost [miso-2026-pra-release].

Cash-flow calendar for a downstate Illinois grow

MISO capacity billing rarely matches how cultivators think about harvest cycles. A supplier smoothing annualized $126.19/MW-day charges equal monthly installments [miso-2026-pra-release]. Your internal cash model should still map June through August when summer clearing was $424.30/MW-day in LRZ 1-7 [miso-2026-pra-release].

Illustrative monthly capacity pass-through on 0.5 MW obligation:

Month	Season	Modeled $/MW-day	Approx. capacity invoice
June	Summer	$424.30 [miso-2026-pra-release]	$6,365
July	Summer	$424.30 [miso-2026-pra-release]	$6,577
August	Summer	$424.30 [miso-2026-pra-release]	$6,577
March	Spring	$7.61 [miso-2026-pra-release]	$118

CUB's consumer-facing explainer tied Ameren price spikes to MISO capacity embedded in default supply [cub-ameren-2026]. If you shop supply for 2027/28, require the seasonal schedule above in the supplier proposal, not only an annual average [enel-miso-2026-27]. ComEd customers in northern Illinois remain on PJM RPM, not this seasonal stack [cub-ameren-2026].

MISO reported the 2026 PRA cleared 3.5 percentage points above the summer Planning Reserve Margin target of 7.9% [miso-2026-pra-release]. Surplus at the ISO does not cap your supplier's pass-through if RBDC pricing cleared tight in summer [utility-dive-miso-2026]. Treat annualized averages as planning tools and summer months as cash-flow stress tests [enel-miso-2026-27]. Fall cleared at $33.92/MW-day and winter at $35.97/MW-day in LRZ 1-7, far below summer, which is why true-up invoices in October can confuse operators who forgot the seasonal stack [miso-2026-pra-release]. Ask your supplier which season each monthly adjustment references when reconciling a confusing autumn invoice [enel-miso-2026-27].