Each utility decides independently
In states with a statutory requirement, the differences between utilities sit above a common floor. Every customer knows at least what they are entitled to.
South Dakota has no such floor, so the variation between utilities is unbounded in both directions. One may offer terms comparable to a net metering state; another may offer little.
Black Hills Energy operates in South Dakota alongside NorthWestern Energy, rural electric cooperatives and municipal utilities, and each sets its own approach.
Check the utility name on a recent bill and treat everything about exports as unknown until that utility tells you otherwise in writing.
Why cross-state comparisons mislead here
Black Hills Energy also serves parts of Colorado and Wyoming, and its arrangements there are shaped by those states rules rather than by South Dakota absence of them.
In Colorado, for example, Black Hills has offered monthly settlement with sizing to 120 percent of average annual usage and a separate renewable energy credit payment. None of that automatically travels.
So a figure found for the same utility in a different state is not evidence of what applies at your South Dakota address.
Ask specifically for the South Dakota arrangement, in writing, and do not let a quote import terms from a neighbouring state.
Then design around the answer
If the answer is favourable, with credit at or near the retail rate, sizing can follow your annual consumption as it would in a net metering state.
If exports are credited at a low rate or not at all, size to your daytime load, because generation your household does not use contributes little or nothing.
Ask for both versions modelled if the utility answer is not yet in hand, so you can see the range rather than a single figure resting on an assumption.
And ask for the self-consumption share stated in either case, since it is the portion of the value that does not depend on the utility decision.
What the arithmetic rests on here
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase in Rapid City receives no federal tax credit, and South Dakota has no state solar tax credit.
Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements, so ask what a provider claims and what reaches you in the rate.
What exists with certainty is the retail value of self-consumed generation. Everything about exports comes from your own utility.
Get the South Dakota arrangement specifically, in writing, and do not accept terms imported from the same utility operations in another state.