Why sizing is easier here
In avoided-cost states, exported electricity is worth a fraction of consumed electricity, so a system matched to annual usage still gives away much of its midday output.
Delaware credits net metering in kilowatt hours for residential systems up to 25 kW, so an exported kilowatt hour returns as a kilowatt hour rather than as a discounted payment.
That means timing matters far less, and annual consumption is a valid basis for sizing rather than an approximation that loses value.
It is a genuinely better position than most of the states covered on this site, and it is worth recognising rather than assuming Delaware works like everywhere else.
What still sets the ceiling
Your own consumption. Credits that exceed what you use across a year are not obviously valuable, so ask what happens to surplus under your utility tariff and whether there is any annual reconciliation.
The grant cap, on the Delmarva side, where $6,000 is reached at roughly 8.5 kW. Beyond that the grant contributes nothing further, though the system still generates.
Capital. Capacity you never use is money spent producing electricity that sits as credit rather than reducing a bill.
Ask what percentage of your annual usage the design covers, and ask for a specific reason for anything meaningfully above it.
When sizing ahead is justified
A concrete planned increase in load with a timeline: an electric vehicle, a heat pump, an addition. Those genuinely raise future consumption.
An electric vehicle is the most quantifiable, since you can estimate the annual kilowatt hours it will add reasonably well from your expected mileage.
A heat pump raises winter consumption, which is when the array produces least, so the two do not line up neatly. Under kilowatt hour crediting that mismatch is handled better here than in most states, but it is still worth modelling.
What does not count is a general expectation of using more electricity later. That is a hope rather than a plan, and it is the most common justification offered for an oversized system.
Three pieces, and how they stack
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 Milford receives no federal 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 your municipal utility Green Energy Fund programme, net metering to 25 kW credited in kilowatt hours, and SREC income through the Delaware Sustainable Energy Utility.
Ask for the design built from twelve months of your own bills, with the percentage of annual usage stated and any capacity beyond it justified.