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Interconnection Standards

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Note: The Iowa Utilities Board is conducting an inquiry on distributed generation and interconnection issues under Docket No. NOI-2014-0001

The Iowa Utilities Board (IUB) adopted rules for utilities in May 2010 for the interconnection of distributed generation facilities in Iowa.

Rate-Regulated Utilities

Rate-regulated utilities include the state's two investor-owned utilities, MidAmerican Energy and Interstate Power and Light (IPL), and Linn County Rural Electric Cooperative, which opted to have the IUB set its rates. The rates of municipal utilities and other rural electric cooperatives are not regulated by the IUB.


Interconnection standards for rate-regulated utilities apply to distributed generation facilities of up to 10 megawatts (MW)* that are not subject to the interconnection requirements of the Federal Energy Regulatory Commission (FERC), the Midwest Independent Transmission System Operator, Inc. (MISO), or the Mid-Continent Area Power Pool (MAPP). A distributed generation facility includes qualifying facilities (QFs) under the U.S. Public Utilities Regulatory Policy Act (PURPA) and alternative energy production (AEP) facilities, which are electricity generation facilities that derive at least 75% of their energy input from solar, wind, waste management, resource recovery, refuse-derived fuel, agricultural crops or residues, or wood burning, as well as dam-based hydroelectric facilities.

The Iowa rules set four levels of review for interconnection requests. A project must meet all of the requirements of a given classification in order to be eligible for that level of review. The level of review required is generally based on system capacity, whether system components are certified by a nationally recognized testing laboratory (NRTL), and whether the system is connected to a radial distribution circuit or to an area network. The basic definitions for each tier are as follows (see IAC § 199-45 for full details):

  • Tier 1: Lab-certified, inverter-based systems with a capacity rating of 10 kilowatts (kW) or less;
  • Tier 2: Lab-certified systems with a capacity rating of 2 MW or less, connected to a radial distribution network or a spot network serving one customer;
  • Tier 3: Lab-certified, inverter-based systems with a capacity rating of 50 kW or less which are connected to an area network and which will not export power; or lab-certified, non-exporting systems connected to a radial distribution circuit where the aggregate total of all generator nameplate capacity is no more than 10 MW (including the distributed generator applicant); and
  • Tier 4: Systems with a capacity of 10 MW or less that do not meet the criteria for inclusion in a lower tier, including all systems using non-lab-certified components and those that require additional construction by the utility in order accommodate the facility.

The rules adopt IEEE 1547-2003 as the technical standard for evaluating interconnection requests. Systems are considered to be lab-certified if the equipment has been tested successfully in accordance with IEEE 1547.1 or certified as compliant with UL-1741 by a nationally recognized testing laboratory (NRTL). The rules also specify the technical screens which may be applied to applications at each level of review as well as time limits for different stages of the evaluation process. Generally speaking, the higher the tier, the more intensive the screening process and the longer the time it takes for an application to be approved.

Disconnect Device

A lockable external disconnect switch (EDS) may be required at the utility's discretion, and the utility is permitted to make reasonable system monitoring and control requirements for systems larger than 1 MW. In addition, systems with a design capacity of 100 kW or less must be equipped with a device that automatically disconnects the system from the electric grid upon a loss of utility-supplied voltage.

In 2015, Iowa enacted H.F. 548, which required the IUB to implement rules requiring distributed generation installations placed in service on or after July 1, 2015, have a disconnection device installed at a location that is easily visible and adjacent to an interconnection customer's electric meter. 


The IUB develops standardized interconnection applications and agreements. Application fees are set at $50 for Level 1 applications; $100 plus $1 per kW for Level 2 applications; $500 plus $2 per kW for Level 3 applications; and $1,000 plus $2 per kW for Level 4 applications. Utilities are required to designate a point of contact for system interconnections and provide contact information on the utility web site.

Liability Insurance

All applicants are required to provide proof of some type of general liability insurance as part of the interconnection agreement. For facilities of less than 1 MW, homeowner's insurance is referred to by the rules as one acceptable form of general liability insurance without any specific minimum amount of coverage. For facilities of 1 MW or larger, the customer must maintain a general liability insurance policy with a limit of at least $2,000,000 per occurrence and at least $4,000,000 in aggregate and name the utility as an additional insured party.

Non-Rate-Regulated Utilities

General interconnection rules that apply to both rate-regulated and non-rate-regulated utilities in Iowa are found in IAC § 199-15.10 and cover QFs and AEP facilities. The rules are limited in scope, covering power quality and safety issues such as specifying the use IEEE 1547-2003 as the technical standard for interconnection evaluations, allowing utilities discretion to require the installation of an EDS, requiring facilities of 100 kW or less to have automatic disconnect capability upon the loss of grid voltage, granting utilities site access rights for inspection and testing, and allowing utilities to disconnect facilities in emergency situations.

Beginning January 1, 2013, all AEP facilities must provide advanced notice of facility construction or installation. Facilities that will be attached directly or indirectly to an electric transmission or distribution line in a public utility's service territory must notify the utility at least a 30 days prior to the commencement of construction or installation. Facilities with a power purchase agreement with the utility are exempt from this requirement. 

*The actual language of the rules states generation capacity in terms of MVA or kVA, as opposed to MW or kW. In addition, while the standard rules only apply to systems up to 10 MW, they state that interconnection of larger facilities should take place using the Level 4 review process and agreement as a starting point, supplemented with mutually agreed upon modifications on the part of the customer and the utility.