The statute puts the numbers in front of you
Act 278 requires a proposal to include the nameplate generating capacity and the expected monthly and annual output, plus annual degradation estimates.
That is more than most states require, and it means an Arkansas buyer starts with the production figure written down rather than having to extract it.
It also means an internally inconsistent proposal is easy to spot. A stated annual degradation figure and a savings model holding production flat for twenty-five years cannot both be right.
Ask which of the two the savings projection actually used. If the model ignores the degradation the proposal states, the back half of the projection is overstated.
Checking the production figure itself
Ask what data source produced it and whether it applies location-specific irradiance for your address rather than a regional average.
Ask what shading analysis was done and what it assumed about tree growth over the system life. North-west Arkansas lots are frequently wooded and a model built on today canopy will overstate output in ten years.
Ask what module temperature the estimate assumed and what temperature coefficient it applied. Panels lose efficiency as they heat, and an Arkansas summer is exactly the condition where a generic model overstates output.
Ask what soiling losses it applied. A model assuming none is describing a cleaner environment than the one your panels will sit in.
And the rate on the other side
Ask which retail rate the projection used and check it against a recent bill. Arkansas averages around 14.2 cents per kWh, but your own rate is the one that matters.
Ask whether fixed monthly charges were included, since they do not fall when consumption does, and ask how the model treated exports, which earn avoided cost rather than retail.
Act 278 requires forecast monthly and annual bill savings in dollars, so that figure should be stated. Ask what rate and what export assumption produced it.
Ask what escalation the projection applied and to see it at zero. With no incentives left, the escalator is the only other lever a quote can pull to make the numbers look better.
What the number should be built from
Strike the federal residential credit from any quote showing it, and do not expect a state credit in its place, because Arkansas has none.
Rebuild from full retail value for self-consumed generation, avoided cost for exports under the non-legacy schedule, and the electricity you stop buying at your actual rate.
Ask your county assessor how residential solar is treated for property assessment at your address, since that is administered locally.
Then use the five business days Act 278 gives you to check the stated output, degradation, cost, payback and savings figures against each other. An internally inconsistent proposal is the easiest kind of problem to catch.