Where the marginal return falls
A house always has some baseline load, so the first kilowatt hours a system produces are the ones most likely to be consumed directly. Those offset a retail purchase.
As the system grows, more of its midday output exceeds what the household is drawing, so the marginal panels produce mostly exports, compensated at avoided cost.
Both cost the same to install. So at some point an additional panel is producing electricity worth a fraction of retail while costing full price, and that is where a bigger system stops being a better one.
Ask your installer to show the return on the last kilowatt of proposed capacity separately from the return on the first. That comparison is what a sizing decision actually rests on.
Start from your bills, not your roof
Act 278 requires a proposal to state expected monthly and annual output. Ask for your own consumption alongside it, month by month, from your last twelve bills.
Those two series side by side show directly how much of the generation your household absorbs and how much leaves at avoided cost. That is the real output of the design work.
Ask what percentage of your annual usage the design covers, and ask for a smaller system modelled alongside the proposal so you can compare returns rather than assume.
A concrete planned increase in load is the good reason to size ahead: an electric vehicle, a heat pump, an addition. A general expectation of using more electricity is not.
The efficiency measures the statute makes you look at
Act 278 requires a proposal to include energy efficiency audit results and available efficiency measures. That requirement is unusual and it is genuinely useful.
Efficiency work is often cheaper per dollar saved than generation, and it reduces the consumption a solar system has to cover, which under this tariff means a smaller and better-matched array.
So read that section of the proposal rather than skipping to the panel count. If the audit identifies meaningful measures, doing them first may change what system size is right.
Ask whether the proposed system was sized before or after the efficiency measures were considered. Sizing to a consumption figure you are about to reduce is a common and expensive sequencing error.
What the number should be built from
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 Conway receives no federal tax credit, and Arkansas 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 is full retail value for self-consumed generation, avoided cost for exports under the non-legacy schedule, and the electricity you stop buying at around 14.2 cents per kWh.
Ask for the design built from twelve months of your own bills, the efficiency measures considered first, and a smaller system modelled alongside the proposal.