Ameren Illinois for Cannabis Facilities: DS-2, DS-3, and DS-4 Delivery, Hourly Default Supply, and MISO

Service area and grid operator

Ameren Illinois serves central and southern Illinois, including Springfield, Peoria, Champaign, and the Metro East across from St. Louis, and sits in the MISO grid rather than PJM [il-plugin-illinois]. That geography covers a large share of the state's cultivation footprint, because land and industrial buildings downstate are cheaper than in the collar counties. Ameren, like ComEd, is on a CEJA multi-year rate plan with delivery charges moving on the schedule approved in ICC Docket 23-0082 [icc-ceja]. Its delivery rates now point to an appendix in the Rate PBR-R tariff for each year's dollar figures [ameren-ds3-tariff], which is why this page describes the structure and does not print per-kW numbers.

The three delivery rates that matter

Rate	Who is in it	Distribution delivery basis
DS-2 Small General Delivery Service	Maximum monthly demand under 150 kW; a customer with no demand meter is assumed to qualify while average use is under 1,200 kWh per day [ameren-ds2-tariff]	Per kWh on all usage [ameren-ds2-tariff]
DS-3 General Delivery Service	Demand metering installed and maximum monthly demand of 150 kW or more but less than 1,000 kW [ameren-ds3-tariff]	Per kW of billing demand, until the January 2027 billing period [ameren-ds3-tariff]
DS-4 Large General Delivery Service	Maximum monthly demand of 1,000 kW or more in two or more of the prior calendar year's twelve billing periods [ameren-ds3-tariff]	Per kW (see the DS-4 tariff sheet)

A dispensary is a DS-2 account. A craft grow with a full lighting and HVAC plant is a DS-3 account. A cultivation center is DS-4. An extraction lab is the account that can go either way, and the Illinois extraction page is built around that fact.

How Ameren decides your class, and when

Ameren reassigns delivery rates once a year, effective with the June billing period, based on demand in the prior calendar year [ameren-ds2-tariff] [ameren-ds3-tariff]. The rules:

• A DS-2 customer with maximum monthly demand of 150 kW or more in two or more of the twelve monthly billing periods moves to DS-3 [ameren-ds2-tariff].
• A DS-3 customer that did not reach 150 kW in at least two months moves down to DS-2; one that reached 1,000 kW in two or more months moves up to DS-4 [ameren-ds3-tariff].
• Once reassigned, a customer is not eligible to return to the prior rate for a minimum of twelve monthly billing periods [ameren-ds2-tariff] [ameren-ds3-tariff].

For a grower the practical reading is that January through December of this year decides June of next year through May of the year after. Two summer months over a line commit the account for at least a year. The peak demand vs. peak usage page explains why the trigger is a half-hour, not a month's energy.

Billing demand and the 2027 change to kVA

On DS-3, the distribution delivery charge is applied to billing demand, which the tariff defines as the higher of the maximum demand occurring on-peak in the billing period or 50 percent of the maximum demand occurring off-peak [ameren-ds3-tariff]. Assume a grow with 500 kW of lighting that runs 7 p.m. to 7 a.m. and 200 kW of daytime load. On-peak maximum is 200 kW; half the off-peak maximum is 250 kW; billing demand is 250 kW. Overnight lighting cut the billing demand in half compared with a daytime schedule, but did not eliminate it.

From the January 2027 billing period, the DS-3 distribution delivery charge moves to a per-kVA basis using apparent demand, computed the same way, with a power factor penalty and a rate limiter [ameren-ds3-tariff]. Apparent demand includes reactive power. A facility full of LED drivers, variable-frequency drives, and lightly loaded motors can carry a power factor well below unity, and after 2027 that will be billed. The power factor page covers correction; 2026 is the year to measure it.

Two more delivery items on DS-3: a per-kW transformation charge when Ameren owns the transformer, and a rule that from January 1, 2026 new company-owned transformation is available only through Rider EFC, the excess facilities rider [ameren-ds3-tariff]. A grow in buildout should get a written answer on who owns the transformer before the electrical drawings are final.

Default supply: BGS below 150 kW, hourly above it

For DS-2, a customer who takes supply from Ameren is served under Rider BGS or the real-time pricing option [ameren-ds2-tariff]. BGS is a fixed price that reflects wholesale power obtained by Ameren through Illinois Power Agency procurement, and Ameren describes it as available to residential and small commercial customers with demand under 150 kW [ameren-business-choice]. The ICC publishes Ameren's residential Price to Compare, 11.326 cents per kWh for the first 800 kWh from June 1 through September 30, 2026, combining 8.2 cents of supply and 2.765 cents of transmission [plugin-ptc-ameren]. A DS-2 business account has its own BGS rate; read it from the bill.

For DS-3 and DS-4, a customer who takes supply from Ameren is served under Rider HSS, Hourly Supply Service [ameren-ds3-tariff]. Rider HSS prices energy at the MISO day-ahead locational marginal price for the Ameren delivery point, applied to a day-ahead nomination of expected hourly usage, with deviations settled at MISO real-time prices, plus applicable MISO uplift and fee charges [ameren-rider-hss]. It also bills a capacity charge against each customer's planning-load contribution, the kW value representing the account's share of the forecast MISO system peak, for each of four planning seasons beginning June 1 [ameren-rider-hss]. Ameren notes that hourly prices are generally highest between 5 a.m. and 9 p.m. daily and during June through September [ameren-business-choice].

Hourly supply is not automatically bad for a grow. A facility with a flat overnight load can do well on it. What it does not provide is a known number for the budget, which is why most DS-3 grows sign a fixed or block-and-index contract with a certified supplier and keep the MISO capacity tag in mind when they set the summer schedule.

Metering and interconnection notes

• Demand metering is a condition of DS-3 [ameren-ds3-tariff]. A DS-2 customer without a demand meter is presumed under 150 kW only while average use stays below 1,200 kWh per day; above that, expect a demand meter and a class review [ameren-ds2-tariff].
• Rate Zone differences. Ameren Illinois is the merger of three legacy utilities, and the tariffs still carry rate-zone provisions, for example a Rate Zone I rule on customer-owned transformation measured at high voltage [ameren-ds3-tariff]. Ask which zone your premises is in.
• On-site generation interacts with the capacity charge through the planning-load contribution, which is measured at MISO peaks. Solar that is producing at 4 p.m. on a July weekday lowers next year's capacity cost; solar that is not does not.

Efficiency programs run by Ameren

Ameren's business energy efficiency program offers standard incentives for lighting, HVAC, and refrigeration and custom incentives for process improvements [ameren-ee-business]. For a DS-3 grow, the projects worth pricing first are the ones that reduce billing demand: dehumidification efficiency, chiller staging, and variable-speed drives on air handlers. Confirm current measure lists and pre-approval steps with the program before committing capital.

How a supplier contract works with Ameren billing

A supplier customer on DS-3 still pays Ameren the customer charge, meter charge, transformation charge if applicable, and the distribution delivery charge every month; the supplier becomes responsible for transmission service charges under the transmission provider's FERC tariffs [ameren-ds3-tariff]. Ameren offers three billing arrangements: dual billing with two bills, a single bill from the supplier that includes Ameren's delivery charges, or utility consolidated billing where Ameren's bill carries the supplier's charge [ameren-business-choice].

To switch, the supplier submits an electronic enrollment transaction to Ameren once you have agreed, and you have 10 calendar days from the date Ameren processes it to contact Ameren and cancel [ameren-business-choice]. The step-by-step procedure is on the Illinois switching guide. For operators with sites on both sides of the state, the ComEd page covers the PJM half, and the Illinois rate page sets the two utilities side by side. Tariff provisions here were verified on 2026-09-11 against the sheets cited; Ameren revises them on ICC dockets, so check the current sheet before relying on a specific term.

DS-3 kVA transition in January 2027

Ameren Illinois will bill DS-3 distribution delivery on apparent demand in kVA with a power factor penalty starting with the January 2027 billing period [ameren-ds3-tariff]. LED drivers, VFD compressors, and legacy HID ballasts with poor power factor can inflate billed demand even when real kW drops after a retrofit. Specify fixtures and HVAC with published power factor or add correction at the panel before the rule change. See power factor penalties.

MISO planning-load contribution on Rider HSS

DS-3 and DS-4 customers on utility default supply take Rider HSS hourly pricing in MISO [ameren-rider-hss]. Each account carries a planning-load contribution, a kW share of the forecast system peak, and pays a capacity charge against it each planning season starting June 1 [ameren-rider-hss]. A single August afternoon sets that tag for the year. Supplier contracts should state whether MISO capacity is fixed or passed through at cost [ameren-business-choice].