By: Deniz Comez, Lead Designer, Ideal Energy

In March we published Changes Coming to Solar Net Metering: Inside the Technical Calculations to walk our readers through the math behind our assessment of the impact of the new net metering rules in Iowa. Since that post was published there have been some updates, as the new tariff has come into effect.

Overview

Although the Iowa Utilities Board (IUB) refused to reconsider its ruling, it did compel Alliant Energy to modify some aspects of the new net metering rules. These changes have lessened the severity of the reduction to net metering. This means solar is still viable for most customers.

Although we’re disappointed that Alliant Energy and the IUB have enacted new rules unfriendly to businesses and homeowners pursuing solar, we’re relieved that the impact won’t be as severe as it could have been.

But before we dive into the specifics, let’s get caught up on the background.

Background & Timeline

In July 2016, the Iowa Utilities Board instructed Iowa’s utilities to submit new net metering rules for consideration as part of a pilot project meant to expand solar power distributed generation in the state. In February 2017, the IUB accepted Alliant Energy’s proposal. Alliant’s proposed rules limit the size of new solar installations by introducing a load cap to net metering.

Calculations based on Alliant’s publicly filed data showed that the new rules reduced the viable size of solar installations by 62% for Residential customers and 68% for General Service customers compared to what would have been installed under the old net metering rules. For an in-depth discussion of the impacts of Alliant’s proposal see our previous post here.

Leaders in the solar industry, environmental organizations, and concerned citizens roundly criticized Alliant’s proposal. Although the IUB did not reconsider its ruling, these efforts were not all in vain. In March the IUB issued a ruling that required Alliant Energy to provide additional information and to make several changes to its proposal.

Alliant made those changes and the new, final rules went into effect on May 1st.

What changed under the revised rules?

The IUB ordered Alliant Energy to provide additional information about the class load data that the net metering load caps are based on. Furthermore, under direction from the IUB, Alliant now defines it’s load caps in terms of alternating current (AC) instead of direct current (DC), which we view as a positive change.

Class load data includes total kWh usage and non-coincident kW demand for all Alliant customers in a particular class, for example the “Residential” class or the “General Service” (commercial) class. This is important for calculating the net metering load cap, because although Alliant would prefer to use an individual customer’s actual kW demand, most customer’s electricity meters don’t measure demand. Instead, Alliant plans to infer a customer’s kW demand from the class load data.

Calculations using Alliant’s newly released class load data show that the net metering load caps won’t be as extreme as the older data had indicated.

We now calculate that net metering will be reduced by 17% for Residential customers and 34% for General Service (commercial) customers. For both cases, the Residential and General Service customers, assume the industry-standard solar generation rate of 1200 kWh for every kW DC of solar installed and the solar installation would have a 1.15 DC to AC ratio.

Although this is not the catastrophe that a 62-68% reduction would have been, we are nevertheless frustrated and disappointed that the IUB and Alliant Energy turned a pilot project meant to promote solar power into a new set of rules that will instead limit solar power. Let’s take a closer look at the math behind these net metering reductions.

Residential net metering reduction calculations

NEW SOLAR NET METERING TARIFF

Under the new tariff, 7.234kW AC of the same 10 kW installation is eligible for net metering with Alliant Energy, saves $1,353 in the first year, and takes 10-11 years to pay for itself. The design lifecycle of solar is 25 years.

A Residential customer that uses 12,000kWh in a year would need approximately 8.696kW AC to be net metered under the old rules to have 100% of their energy usage net-metered. This is calculated like so:

Given that the Load Factor for Residential customers Load Factor is now 18.937%, under the new rules, the client can have the Load Cap of:

General service net metering reduction calculations

A General Service customer that uses 120,000kWh in a year would need approximately 86.957kW AC to be net metered under the old rules to have 100% of their energy usage net-metered. This is calculated like so:

Given that the Load Factor for General Service customers Load Factor is now 23.855%, under the new rules, the client can have the Load Cap of:

NEW SOLAR NET METERING TARIFF

Under the new rules, 57.425 kW AC of the same 86.6kW AC installation is eligible for net metering, saves the business $13,105 in the first year and takes 5-6 years to pay for itself. The design lifecycle of solar is 25 years.

Final thoughts on the new ruling

• These new metering rules don’t spell the end of solar power in Iowa. While the rules represent a step backward, solar nevertheless continues to be a prosperous opportunity for many Alliant customers.
• If you are an Alliant Energy customer and already have solar, no worries, you’re grandfathered in under the old tariff through your interconnection agreement.
• The outlook is especially good for customers of MidAmerican Energy, another large public utility in Iowa. MidAmerican has implemented new rules that support and encourage solar power. We think they’re moving in the right direction.
• If you’d like to know more about how these net metering changes affect your plans to pursue solar, don’t hesitate to get in touch.