Illustrative Case: ComEd Craft Grower Restructures Demand Before Supply Shopping

The facility and starting situation

Assume a social-equity craft grower in suburban Cook County on a ComEd account in PJM [il-plugin-illinois]. The license fits the Illinois pattern: all 87 craft grower licenses issued through FY2025 went to social equity applicants, and 21 of those craft growers were operational at the report date [il-annual-cannabis-report-2025]. The building is 28,000 square feet with 10,000 square feet of flowering canopy, 3,000 square feet of veg, and a mother room. Lighting is LED at an assumed 35 watts per square foot in flower, 25 W in veg, and 20 W in the mother room. HVAC and dehumidification are sized for Illinois humidity: the state averages 6,105 heating degree days and 889 cooling degree days, with summer dew points in the 60s and 70s F [noaa-cag-illinois].

At energization the operator ran every flower room on the same 6 a.m. to 6 p.m. photoperiod. Interval data showed a summer peak of 640 kW and a winter peak of 550 kW. That placed the account in ComEd's Large Load delivery class, which covers peak demand from 401 to 1,000 kW [comed-delivery-charges-guide]. Supply was arranged through a retail electric supplier under Rate RDS, which is how ComEd expects larger nonresidential classes to buy power [comed-rate-rds]. The operator had signed a one-year fixed supply contract before anyone reviewed the delivery side of the bill.

What the baseline bills showed

The table below mixes cited tariff rates with assumed usage. Only the rates and class thresholds are facts; kWh, kW, and dollar totals are inputs for this example.

Line item	Assumption or rate	Monthly (summer)	Monthly (winter)	Notes
Flower lighting	350 kW on 12 h/day	127,750 kWh	127,750 kWh	Assumed load
Veg and mother	40 kW on 18 h/day	21,900 kWh	21,900 kWh	Assumed load
HVAC and dehumid	210 kW summer / 120 kW winter avg	151,200 kWh	86,400 kWh	Assumed load
House load	40 kW continuous	29,200 kWh	29,200 kWh	Assumed load
Measured peak demand	640 kW / 550 kW	640 kW	550 kW	Sets delivery class
Distribution facilities charge	$14.95 per kW, Large Load secondary [comed-delivery-charges-guide]	$9,568	$8,223	Delivery only
Customer charge	$34.61 per month [comed-delivery-charges-guide]	$34.61	$34.61
Supply (fixed contract)	Assume 9.8 cents per kWh all-in	~$32,600	~$26,800	Modeled input
Approximate total		~$72,000	~$55,000	Excludes taxes and riders

Annualized, the distribution facilities charge alone was about $104,000: four summer months at $9,568 plus eight winter months at $8,223. That is close to a quarter of the facility's all-in spend at the EIA June 2026 Illinois commercial average of 14.53 cents per kWh on roughly 3.2 million kWh [eia-epm-5-6-a]. The operator had been focused on the supply rate because it was the line the broker quoted. The per-kW delivery charge was buried on page two.

What changed

Three interventions ran in parallel over one quarter.

Staggered photoperiods. Instead of one 640 kW lighting step at 6 a.m., the operator split four flower rooms into two blocks: two rooms on 6 a.m. to 6 p.m. and two on 8 a.m. to 8 p.m. HVAC was rebalanced so each block got its own dehumidifier setpoint ramp. Peak demand fell because the lighting step and the compressor start no longer stacked in the same 30-minute window ComEd uses for billing [il-plugin-illinois]. See peak demand vs. peak usage for why interval shape matters.

Targeted LED retrofit with ComEd incentives. Two older veg rooms still ran mixed fixtures at roughly 45 W per square foot. Replacing them with DLC-listed horticultural LEDs at 30 W cut 22 kW from the continuous load. ComEd's business efficiency program lists horticultural LED fixtures meeting DLC horticultural listing and efficacy requirements among its standard incentives [comed-ee-business]. The rebate did not pay for the whole project, but it shortened payback enough to get board approval.

Rate-class and voltage review. An engineer confirmed the account was correctly billed at secondary voltage. Primary service would have required a capital upgrade the operator could not fund. The review still mattered: the team verified that a planned fifth flower room would not push peak demand past 800 kW without another stagger block, which would have changed the supply quote's capacity pass-through in PJM [il-plugin-illinois].

Only after interval data showed two months of lower peaks did the operator renew supply. The new contract was a 24-month fixed price with an ARES certified by the Illinois Commerce Commission [il-plugin-illinois]. Customers on supplier contracts are not subject to the utility's Purchased Electricity Adjustment [il-plugin-illinois].

The math after

Assume the stagger and LED work cut summer peak demand from 640 kW to 520 kW and winter peak from 550 kW to 470 kW. The account remained in Large Load, but the per-kW charge applied to a smaller number.

Line item	Before (summer month)	After (summer month)	Change
Peak demand	640 kW	520 kW	−120 kW
Distribution facilities charge	$9,568	$7,774	−$1,794
Annual distribution facilities	~$104,000	~$89,500	~−$14,500
Supply (same 9.8 cent contract)	~$32,600	~$31,900	−$700 (lower kWh)
Modeled annual all-in	~$465,000	~$448,000	~−$17,000

The kWh reduction from the LED retrofit was modest, about 96,000 kWh a year in the veg rooms. The demand reduction drove most of the delivery savings. At the EIA Illinois industrial average of 10.65 cents per kWh, the same kWh stack would cost less on paper [eia-epm-5-6-a], but the operator still faced Large Load delivery charges because peak kW, not kWh, sets the class [comed-delivery-charges-guide].

Delivery rates will move again under the Climate and Equitable Jobs Act multi-year rate plans the ICC approved in dockets 23-0055 and 23-0082 [icc-ceja]. Treat the per-kW figures as the shape of the bill, not a permanent quote.

What did not work

Running all lights at night. ComEd bills Large Load on the highest 30-minute interval in the month, not a time-of-day split [comed-delivery-charges-guide]. A 10 p.m. to 10 a.m. photoperiod did not remove the demand charge and created staffing problems the operator abandoned after six weeks.

Demand-response enrollment. PJM programs pay for curtailment, but a flowering room cannot drop 350 kW for four hours without crop risk. The operator enrolled once, declined to shed during a test event, and paid a nominal penalty.

Rooftop solar for peak shaving. Illinois Shines offers REC contracts for on-site generation [illinois-shines], but the roof fit roughly 150 kW of modules, not enough to cover a 520 kW peak lasting twelve hours. Interconnection and insurance pushed the quote below the hurdle rate.

Switching supply first. The first broker quote saved 0.4 cents per kWh, about $13,000 a year on 3.2 million kWh. That was smaller than the delivery work and locked the operator into a term before peaks were managed.

CEJA delivery rate updates

ComEd delivery charges move under Climate and Equitable Jobs Act multi-year rate plans approved by the ICC [icc-ceja]. Re-run peak kW and per-kW cost after each effective date. Staggered rooms still help even when the per-kW rate rises; the multiplier applies to a smaller peak [comed-delivery-charges-guide].

Ameren parity note

This example uses ComEd Large Load thresholds. Ameren Illinois uses different demand class breakpoints on its delivery tariff. Staggered rooms and LED incentives follow the same logic in Ameren territory; verify per-kW rates on the current tariff book before copying dollar results [il-plugin-illinois].

Documenting stagger changes for the board

Save interval charts before and after photoperiod offset. ComEd bills Large Load on highest 30-minute interval [comed-delivery-charges-guide]. Board approval for LED capex often needs kW reduction proof, not just kWh savings estimates from fixture specs.

Revisit after fifth flower room

The example notes verifying a fifth room would not push peak past 800 kW without another stagger block [comed-delivery-charges-guide]. Expansion planning should include interval modeling before permit submission for additional canopy.

Lessons that transfer to other Illinois grows

Read the delivery class before you sign supply. ComEd Medium Load covers 101 to 400 kW and Large Load covers 401 to 1,000 kW [comed-delivery-charges-guide]. Stagger rooms before you buy equipment upgrades; shifting one flower schedule costs nothing except controller programming. Match ComEd LED incentives to the load you keep and apply before you purchase [comed-ee-business]. Re-run interval analysis after each CEJA rate update [icc-ceja]. Supplier choice is the second move: full commercial choice is available on ComEd [il-plugin-illinois], but a fixed contract does not shrink the distribution facilities charge. See demand charges explained and the FAQ on lowering grow bills.