Top Takeaways
1-to-1 Net Metering
Excess credits rollover until January or April (your choice)
April is generally recommended
Iowa's Net Metering Policy
Under Iowa’s Inflow Outflow Tariff, excess solar production will ‘net,’ or subtract, with consumption 1-to-1 at the same retail rate per kWh the utility charges you (as long as your system is not oversized). You will always have a monthly electric bill to cover base customer charges ($10-$20) regardless of how much your solar system produces.
January or April Annual Period
If you produce more solar than you consume during a month, excess credits will rollover until you can use them. After 12 months, any excess credits will be forfeited with no cash payment. The 12 month annual period ends in January or April based on your selection in the utility’s Interconnection Application. Your installer submits the Interconnection Application to the utility on your behalf after you sign it.
April is recommended for your annual net metering period,
however, it's your choice.
Why is April recommended?
April is generally recommended for your annual period, because solar for typical homeowners will produce excess credits in the fall months to offset winter consumption. If your annual period is in January, you may lose some net metering credits that could have offset February or March bills.
Solar production is at its peak in the summer months when the days are long and sunny. In the winter, production is lower due to clouds, snow, and less sun hours. An April cycle typically enables credits to build throughout the year, and offset winter consumption.
Monthly NEM credit illustration
Monthly NEM credit illustration
The above example illustrates a typical production and consumption profile in the mid-west with a system designed to produce 98% of the home's annual usage. For this home, May to September net metering credits will have the opportunity to offset consumption during the winter months.
If April is chosen, only a small amount of kWh credits will be forfeited to the utility (removed from the NEM bank).
If January is chosen, more credits would be forfeited, and February would not have any credits to offset kWh usage charges.
Oversized Solar Systems
Iowa’s Inflow Outflow Tariff has a 110% rule to be aware of. Your installer is required to collect 3 years of electric usage history (or as much as you have if you have not been in the home for long). The system is allowed to be sized to produce more than your historical consumption, however, any estimated production over 110% of your usage will be credited at a low avoided cost rate of 2-3 cents per kWh.
Sample Bill with an Oversized System (168 kWh credited at $-0.0213 per kWh)
Palmetto LightReach does not recommend oversizing your system. If you do plan to increase your consumption and move forward with an oversized system, you can request Alliant or MidAmerican review your new usage profile to see if your eligibility for full crediting has changed.
Contact Alliant or MidAmerican
To request a review of your usage history or to change your January/April election, please contact your utility at:
Learn More
Visit your utility’s solar interconnection webpages for MidAmerican Energy and Alliant Energy. Alliant’s FAQs and sample bills are great resources.