Illinois Cannabis Cultivation Facility Energy: Lighting, HVAC, and Demand Charges Under ComEd and Ameren

What an indoor grow looks like to ComEd or Ameren

A utility does not see plants. It sees a meter that draws a nearly flat block of power for 12 or 18 hours a day when the lights are on, a smaller block when they are off, and a summer bump when the dehumidifiers and chillers work hardest. That shape has two consequences in Illinois. First, the highest half-hour of demand in the month sets the per-kW delivery charge for any grow beyond the smallest classes. Second, the demand level decides the delivery class, and the delivery class decides what kind of default supply the utility offers.

At ComEd the nonresidential delivery classes are defined by demand: Watt-Hour for under 2,000 kWh a month, Small Load for 0 to 100 kW, Medium Load for 101 to 400 kW, Large Load for 401 to 1,000 kW, Very Large Load for 1,001 to 10,000 kW, and Extra Large Load at 10,001 kW and above [comed-delivery-charges-guide]. At Ameren Illinois, Rate DS-2 covers customers with a maximum monthly demand under 150 kW, Rate DS-3 covers 150 kW up to but not including 1,000 kW, and DS-4 starts at 1,000 kW [ameren-ds2-tariff] [ameren-ds3-tariff]. A cultivation center among the 21 licensed in the state will usually sit in ComEd Large or Very Large Load or Ameren DS-4; most of the 87 craft licenses will land in Medium or Large Load or DS-3 once they energize [il-annual-cannabis-report-2025].

Lighting is the base load, and it sets the class

Assume a craft grow with 10,000 square feet of flowering canopy under LED fixtures at 35 watts per square foot. That is an assumption, not a benchmark; some rooms run 30 W, some run 45 W. Lighting alone draws 350 kW when every fixture is on. Add vegetative and mother rooms at, say, another 40 kW and the lighting load is roughly 390 kW.

That number alone puts the facility near the top of ComEd's Medium Load class or over the line into Large Load, and squarely into Ameren DS-3. The difference between the two ComEd classes is not trivial: the September 2025 customer charge is $23.32 a month for Medium Load and $34.61 for Large Load, and the secondary voltage distribution facilities charge is $14.59 per kW for Medium Load and $14.95 per kW for Large Load [comed-delivery-charges-guide]. Those figures change under the CEJA multi-year rate plan, so treat them as the shape of the bill rather than a quote. The LED vs. HPS comparison covers why the fixture choice moves this number more than any other single decision.

HVAC and dehumidification in a 6,105 heating degree day climate

Illinois runs 6,105 heating degree days and 889 cooling degree days in a normal year [noaa-cag-illinois]. For a sealed room that ratio is unusual. Most of the year the building envelope is losing heat to the outside, which means the lights' waste heat is partly useful and the mechanical cooling plant runs below capacity. Then June arrives. Summer dew points sit in the 60s and 70s Fahrenheit across much of the state [noaa-cag-illinois], and any outdoor air that enters for CO2 makeup, door openings, or leakage carries moisture that the dehumidification system has to remove on top of the water the plants transpire.

The dehumidification load page covers the physics. The Illinois-specific point is timing. The dehumidifier and chiller peak in July and August, and so does the PJM and MISO wholesale market. If you carry a per-kW delivery charge and your supply contract passes through capacity costs, summer is when both hit at once. Continuing the example: assume the HVAC and dehumidification plant draws 210 kW at summer peak and 120 kW on an average day, with 40 kW of pumps, fans, controls, and office load year-round. Summer peak demand is then 390 + 210 + 40 = 640 kW. Winter peak, with the cooling plant loafing, might be 390 + 120 + 40 = 550 kW.

A worked annual cost for the example grow

Every input here is an assumption unless cited. Annual energy:

Load	Assumption	Annual kWh
Flower lighting	350 kW, 12 hours a day, 365 days	1,533,000
Veg and mother lighting	40 kW, 18 hours a day, 365 days	262,800
HVAC and dehumidification	120 kW average across the year	1,051,200
Pumps, fans, controls, office	40 kW continuous	350,400
Total		3,197,400

At the EIA June 2026 Illinois commercial average of 14.53 cents per kWh, that is about $464,600 a year all-in [eia-epm-5-6-a]. At the Illinois industrial average of 10.65 cents it would be about $340,500 [eia-epm-5-6-a]. The 3.9 cent gap between those two averages is the reason this page exists: a grow with a flat, high load factor looks more like an industrial customer, and both its delivery class and its supplier quote should reflect that.

Now the demand component, using ComEd Large Load as the class. Assume 640 kW summer peak and 550 kW winter peak at secondary voltage:

• Summer month: 640 kW × $14.95 = $9,568 in distribution facilities charge [comed-delivery-charges-guide]
• Winter month: 550 kW × $14.95 = $8,223

Four summer months and eight winter months come to roughly $104,000 a year in distribution facilities charges before the customer charge, metering, transmission, and the per-kWh IEDT of $0.00125 [comed-delivery-charges-guide]. That is close to a quarter of the all-in figure above, and none of it is controlled by a supply contract. It is controlled by peak demand. See demand charges explained for the mechanics and HVAC sizing for how oversized cooling plants create peaks that never needed to exist.

CO2 enrichment and the demand it hides

Bottled or bulk CO2 has no direct electric load beyond a regulator and controls. CO2 from a natural gas burner adds heat and water vapor that the HVAC must remove, which shows up as electric load on the dehumidifier. In an Illinois summer that indirect cost is real. Operators who sealed the room and pushed CO2 to 1,200 ppm and above often report that the dehumidification plant, not the lights, sets the July peak. The CO2 supplementation page works the numbers.

Which default supply you get if you do nothing

This is the part that surprises growers moving from other states. At ComEd, the Price to Compare that Plug In Illinois publishes, 10.399 cents per kWh for summer 2026, is a residential number [il-plugin-illinois]. ComEd's Rate RDS tariff makes retail delivery service unavailable to a brand-new applicant that would be a residential, small lighting, Watt-Hour, or Small Load customer until it has first taken bundled service, which is another way of saying the larger classes are expected to arrange supply through a retail electric supplier, the Power Purchase Option, or self-management [comed-rate-rds]. At Ameren, a DS-3 or DS-4 customer that takes supply from the utility is served under Rider HSS, hourly supply priced off the MISO day-ahead market [ameren-ds3-tariff]. Neither is a fixed price. A grow that wants budget certainty on the supply side signs a fixed, index, or block-and-index contract with an ICC-certified supplier, and customers on supplier contracts are not subject to the utility's Purchased Electricity Adjustment [il-plugin-illinois].

Buildout decisions that lock in the bill

Illinois issued every craft grower license through FY2025 to a social equity applicant, and most of those facilities were not yet operational at the report date [il-annual-cannabis-report-2025]. That means a large share of the state's future cultivation load is still on the drawing board. Three design choices matter more than they look:

1. Delivery voltage. ComEd charges a lower per-kW distribution facilities charge at primary voltage than at secondary in the Medium, Large, and Very Large Load classes, offset by a small primary voltage transformer charge if ComEd owns the transformer [comed-delivery-charges-guide]. Owning your own transformer is a capital cost against a lower monthly charge for the life of the facility.
2. Transformation at Ameren. Ameren bills a per-kW transformation charge when it owns the transformer, and from January 1, 2026 new company-owned transformation is available only through Rider EFC, the excess facilities rider [ameren-ds3-tariff].
3. Power factor. From the January 2027 billing period, Ameren's DS-3 distribution delivery charge moves to a per-kVA basis using apparent demand, with a power factor penalty [ameren-ds3-tariff]. LED drivers and variable-speed compressors with poor power factor will cost more after that date than before it. See power factor penalties.

Incentives that reduce the load before you buy supply

Reducing peak kW is worth more in Illinois than reducing kWh, because the per-kW charge is fixed by tariff while the per-kWh supply price is negotiable. ComEd's business efficiency program lists horticultural LED fixtures meeting DLC horticultural listing and efficacy requirements among its standard incentives [comed-ee-business]. Ameren's business program offers standard and custom incentives for lighting, HVAC, refrigeration, and process improvements [ameren-ee-business]. A custom incentive for a dehumidification upgrade is often the better-paying project in this climate.

Growers in neighboring markets face a different mix of climate and tariff. The Michigan cultivation page and the Ohio cultivation page show how the same room prices out under different utilities, and the Illinois rate page lays the ComEd and Ameren classes side by side.