On-site (Distributed) Generation

On-site, customer-owned electric generation installations of solar, wind, and biomass are becoming more popular in Iowa. Many of these facilities connect to the electric grid with coordination from the local utility provider. 

The IUB has regulatory authority over investor-owned utilities, also referred to as rate-regulated utilities, but limited authority of the municipal electric and rural electric cooperative utilities in Iowa. This limited authority covers:

• service
• safety
• engineering issues

If you are a resident or small business considering this type of installation, the Consumer Guide for On-Site Generation offers useful information and links to additional resources to help you make an informed decision about installing on-site generation. 

For solar installations, see the Solar PV Energy Guide for residential or small businesses.

Interconnection

The IUB has rules related to interconnection of on-site generation facilities. The IUB's standards for interconnection, safety, and operating reliability are found in 199 IAC chapter 15 and are applicable to all utilities. 

Additionally, the IUB's rules for Electric Interconnection of Distributed Generation facilities are found in 199 IAC chapter 45. These are applicable to utilities subject to rate regulation by the IUB (such as MidAmerican Energy Company and Interstate Power and Light Company). 

Sample interconnection forms and agreements follow. If you are applying for on-site generation,  check with your electric utility first to determine whether the utility has its own forms to complete.

• Level 1 Interconnection Request Application Form and Distributed Generation Interconnection Agreement 
• Certification of Completion  
• Levels 2-4 Interconnection Request Application Form 
• Levels 2-4 Distributed Generation Interconnection Request Agreement 
• Interconnection Facilities Study Agreement
• Interconnection System Impact Study Agreement
• Interconnection Feasibility Study Agreement

​Net Metering

Net metering refers to a single meter used to monitor the net amount of electricity delivered to, and exported by, an eligible distributed generation (DG) facility. The electricity generated by the DG customer offsets electricity otherwise purchased by the customer from the electric utility. The IUB's rules for net metering are found here: 199 IAC 15.11(5). 

Senate File 583 (Iowa Code § 476.49) requires Interstate Power and Light Company and MidAmerican Energy Company to file net metering tariffs that use either a net billing or inflow-outflow method.

Net billing method:

• The DG customer pays all applicable charges, including applicable riders approved by the IUB for the electricity the utility delivers to the customer.
• Credit is in kilowatt-hours for energy exported to the electric utility during the billing period.
• The DG customer may use the kilowatt-hour credits to offset kilowatt-hours in future billing periods.

Inflow-outflow method:

• The DG customer pays all applicable charges, including applicable riders approved by the IUB for the electricity the utility delivers to the customer.
• Credit is in dollars at the outflow purchase rate for energy exported to the utility during the billing period.
• The DG customer may use the dollar credits to offset any applicable volumetric charges billed on a kilowatt-hour basis in future billing periods.

The IUB has approved these tariffs:

MidAmerican Energy Company

• Docket No. TF-2020-0235, Rate IO – Inflow/Outflow Billing of Eligible Distributed Generation Facilities tariff (approved November 24, 2020)

Interstate Power and Light Company

• Docket No. TF-2020-0237, Inflow-Outflow DG Billing (Rate Code: IO) tariff (approved December 30, 2020)
• Docket No. TF-2020-0238, Revisions to Net Metering Pilot – Renewable Energy Facilities (Rate Code NM) tariff (approved December 30, 2020)

Distributed Generation Penetration Percentage

Iowa Code § 476.49 directs the IUB to:

• collect data on the nameplate capacity of eligible distributed generation facilities,
• calculate the statewide distributed generation penetration percentage, and
• publish the data and penetration rate on an annual basis" on the IUB's website.

The following statewide distributed generation penetration percentage and the penetration percentages were reported by MidAmerican Energy Company and Interstate Power and Light Company on April 29, 2022, in Docket Nos. TF-2020-0235 and TF-2020-0237, respectively:

2022 Distributed Generation Penetration Percentage
	MidAmerican	IPL	Statewide
Installed Distributed Generation Facilities (MW)	43.131 (1)	140.00 (2)	183.131
2020 Peak Demand (MW)	4,981 (3)	2,895 (4)	7,876 (5)
Penetration Rate	0.87%	4.84%	2.33%

Iowa Code § 476.49(4) requires the IUB to develop a value of solar methodology and rate for eligible DG facilities when the statewide distributed generation penetration rate equals 5%, or if the IUB is petitioned by an electric utility after July 1, 2027, whichever is earlier.

(1) Net metering total from the “Alternative Energy Production Facility Report 2020” filed in Docket No. IAC-2023-1511 on March 28, 2023.

(2) IPL’s distributed generation facility total is from IPL’s records and includes facilities enrolled in its AEP Net Metering and Net Metering Pilot tariffs. 

(3) MidAmerican’s Iowa annual peak for 2022 as reported in the “2023 AE Allocator Calculation” report in Docket No. TF-2023-0007 on February 15, 2023.

(4) IPL’s Iowa annual peak demand from FERC Form 1, page 401b.

(5) The IUB is using the sum of MidAmerican’s and IPL’s peak demand as a reasonable estimate for the statewide demand.  The IUB reviewed information filed in MidAmerican’s and IPL’s FERC Form 1, page 401b, to ensure that this peak demand value is a reasonable estimate.  Currently there is nothing filed with the IUB that allows the IUB to determine a statewide coincident peak demand.