ComEd's June–September Summer Price vs. October Non-Summer Price: Seasonal Timing for Illinois Cultivators

ComEd splits the year into summer and non-summer supply

Illinois Power Agency procurements feed ComEd's default supply rate in two seasonal bands. For summer 2026, Plug In Illinois publishes a price to compare of 10.399 cents/kWh effective June 1 through September 30, 2026 [plugin-comed-ptc]. That combines an 8.677 cents/kWh electric supply charge and 1.722 cents/kWh transmission services charge [plugin-comed-ptc].

Non-summer periods use a different blend, typically lower on the supply component. Your annual average depends on how many kWh you consume in each band.

CUB alerted customers that the summer 2026 price rose roughly 50 percent versus two years earlier, citing PJM capacity and wholesale trends [cub-comed-summer-2026]. Cultivation facilities are summer-heavy because dehumidification and cooling peak with outdoor humidity [eia-epm-5-6-a context].

Price to compare is not your total bill

ComEd bills separate:

Section	Shoppable?	Notes
Electric supply + transmission (PTC)	Yes	10.399 summer 2026 [plugin-comed-ptc]
Delivery service	No	Demand kW charges
Taxes and fees	Partially	Renewable Energy Adjustment 0.1722 cents/kWh all customers June 2026 [plugin-comed-ptc]

Switching to an alternative retail electric supplier replaces supply and transmission benchmark components. Delivery demand for large grow loads often dominates when spread at low load factor. See demand charges.

Weighted average math for a grow

Assume monthly kWh split (model inputs):

Month band	kWh/month	Rate used
June–September	180,000 each	10.399 cents
October–May	150,000 each	9.0 cents (example non-summer; verify current PTC)

Summer kWh: 720,000 × $0.10399 ≈ $74,873

Non-summer kWh: 1,200,000 × $0.090 ≈ $108,000

Blended supply+trans ≈ $182,873 / 1,920,000 kWh ≈ 9.52 cents/kWh

A cultivator using 38 percent of annual kWh in summer pays closer to the summer rate than an office building at 20 percent.

When to sign a fixed supplier contract

May (before June 1): Suppliers know summer PTC will jump to 10.399 cents/kWh [plugin-comed-ptc]. Fixed quotes may embed summer risk.

July–August: If index components spike beyond fixed quote, early lock helps. If not, wait.

September: Decide before October non-summer PTC publishes whether to ride default or extend fixed.

October 1: Non-summer benchmark often drops. Starting a fixed contract October 1 can reduce annual average if winter kWh is large.

Compare offers to weighted average, not headline summer cents.

PJM capacity still moves on June 1

Even with seasonal PTC, PJM capacity from the 2026/2027 auction at $329.17/MW-day flows through supplier pass-throughs starting June 1 [enel-pjm-capacity-2026]. Fixed energy does not mean fixed capacity line.

Align June 1 planning with ComEd seasonal PTC review.

Purchased Electricity Adjustment exemption

Default ComEd customers face a monthly Purchased Electricity Adjustment true-up [plugin-comed-ptc]. Supplier customers avoid PEA volatility, one reason fixed contracts stabilize budgeting even at a small premium to summer PTC.

Practical checklist

1. Download twelve-month kWh by billing period from ComEd portal
2. Calculate weighted average vs summer and non-summer PTC [plugin-comed-ptc]
3. Request supplier quotes for 12 and 24 months with capacity pass-through spelled out
4. Compare to Illinois commercial rates context (14.53 cents/kWh average includes delivery) [eia-epm-5-6-a]
5. Calendar October PTC release for renewal decisions

Purchased Electricity Adjustment: default-only volatility

ComEd default customers face monthly Purchased Electricity Adjustment true-ups [plugin-comed-ptc]. The summer price to compare 10.399 cents/kWh is a planning benchmark; actual default bills wiggle with PEA [plugin-comed-ptc]. Supplier customers avoid PEA, one reason a fixed offer slightly above PTC can still stabilize cash flow.

Document PEA exemption in CFO models when comparing default vs supplier.

Renewable Energy Adjustment equalization

Starting June 2026 billing, Renewable Energy Adjustment is 0.1722 cents/kWh for all customers regardless of supply choice [plugin-comed-ptc]. Small line, but proves delivery-side riders apply universally.

Industrial vs commercial rate class on ComEd

Cultivation centers crossing ComEd watt-hour or kilow-delivery thresholds move rate classes [il-plugin-illinois]. Class change resets how demand charges apply. Re-run supplier RFP after class change even if PTC season unchanged.

Ameren contrast within Illinois

Chicago readers on ComEd should not send Ameren advice to Springfield partners. Ameren follows MISO June 1 [miso-june-1 article]. Same state, different ISO, different capacity pass-through.

When October 1 start beats June 1 start

If your load is winter-heavy (veg-only facility, greenhouse supplemental light), non-summer kWh may dominate. Starting fixed supply October 1 captures lower non-summer PTC benchmark on default comparison [plugin-comed-ptc].

If load is summer-heavy (indoor flower with dehumidification), June-start fixed hedge protects high summer kWh months.

Run weighted average with your actual monthly kWh from ComEd portal [plugin-comed-ptc].

Supplier capacity pass-through reminder

PJM 2026/2027 capacity at $329.17/MW-day hits June 1 [enel-pjm-capacity-2026]. Summer PTC embeds some capacity cost; supplier fixed energy may exclude it. Compare all-in effective rate, not headline energy cents.

Three mistakes ComEd cultivators make

1. Comparing supplier offer to summer PTC while using more kWh in winter
2. Ignoring delivery demand when supply saves 1 cent/kWh
3. Auto-renewing supplier contract without checking October non-summer PTC shift

Use Illinois switching guide for enrollment timing.

IPA credits and ComEd bills in 2026

The Illinois Power Agency credited ComEd customers in 2026 through reconciliation mechanisms separate from seasonal PTC [plugin-comed-ptc]. Credits on default bills do not always flow to supplier customers the same way. When comparing offers, ask suppliers how IPA-related adjustments appear, if at all.

Record-keeping for seasonal benchmarks

Save a PDF of the Plug In Illinois PTC page each June and October [plugin-comed-ptc]. If a supplier dispute arises, the published benchmark documents what default would have cost.

Craft grow vs cultivation center load shapes

Craft grows with one or two flower rooms often have sharper summer kWh spikes from portable dehumidifiers than MSO campuses with central HVAC [plugin-comed-ptc]. Weighted average PTC math differs even at the same canopy square footage. Export monthly kWh from ComEd before choosing June vs October contract start.

ComEd's seasonal split rewards cultivators who model load shape, not just who chase the lowest summer sticker price. Build a one-tab spreadsheet with monthly kWh, summer PTC, non-summer PTC, and supplier offer; update it each June and October when Plug In Illinois publishes new benchmarks [plugin-comed-ptc].

Cash-flow difference between default PEA and fixed supplier

ComEd default customers face a monthly Purchased Electricity Adjustment true-up that moves the actual supply charge away from the published price to compare [plugin-comed-ptc]. Supplier customers avoid PEA volatility on the default supply line. That matters for cultivators with tight harvest-week cash flow.

Summer 2026 price to compare is 10.399 cents/kWh for June 1 through September 30, 2026, combining 8.677 cents/kWh supply and 1.722 cents/kWh transmission [plugin-comed-ptc]. CUB noted the summer 2026 price rose roughly 50 percent versus two years earlier, citing PJM capacity and wholesale trends [cub-comed-summer-2026]. A supplier offer at 10.8 cents/kWh fixed looks worse than 10.399 cents/kWh PTC until you model PEA swings and the fact that supplier contracts may exclude capacity pass-through that still updates June 1 [enel-pjm-capacity-2026].

Cost line	Default ComEd	Alternative supplier
Supply + trans benchmark	Seasonal PTC [plugin-comed-ptc]	Contract rate
PEA true-up	Monthly [plugin-comed-ptc]	Not on default line
PJM capacity	Embedded in PTC/pass-through	Often separate [enel-pjm-capacity-2026]
Delivery demand	ComEd tariff	Same

Renewable Energy Adjustment is 0.1722 cents/kWh for all customers starting June 2026 billing regardless of supply choice [plugin-comed-ptc]. Small line, proof that delivery-side riders apply universally.

Illinois average commercial rate was 14.53 cents/kWh in June 2026 including delivery context [eia-epm-5-6-a]. A Chicago indoor grow with 180,000 kWh/month in summer and 150,000 kWh/month in winter should compare supplier offers to a weighted PTC average near 9.5 to 10.2 cents/kWh on supply and transmission only, not to the summer sticker alone [plugin-comed-ptc].

Craft grows with one or two flower rooms often show sharper summer kWh spikes from portable dehumidifiers than MSO campuses with central HVAC [plugin-comed-ptc]. Export monthly kWh from the ComEd portal before choosing June versus October contract start. Three mistakes to avoid: comparing supplier offer to summer PTC while using more kWh in winter; ignoring delivery demand when supply saves one cent/kWh; auto-renewing without checking October non-summer PTC shift [cub-comed-summer-2026].

Save a PDF of the Plug In Illinois PTC page each June and October [plugin-comed-ptc]. If a supplier dispute arises, the published benchmark documents what default would have cost. The Illinois Power Agency credited ComEd customers in 2026 through reconciliation mechanisms separate from seasonal PTC [plugin-comed-ptc]. Credits on default bills do not always flow to supplier customers the same way. Ask suppliers how IPA-related adjustments appear, if at all, before signing multi-year fixed deals.

Cultivation centers crossing ComEd watt-hour or kilow-delivery thresholds move rate classes [il-plugin-illinois]. Class change resets how demand charges apply. Re-run supplier RFP after class change even if PTC season unchanged. Downstate Ameren follows MISO June 1 planning year rules; do not send ComEd seasonal PTC advice to Springfield partners without a separate Ameren benchmark review [il-plugin-illinois].