Orientation you did not choose
In a planned development the position of your house was set by the street layout rather than by solar considerations, so the available roof planes are what they are. Some homes have an excellent southerly plane and some do not.
That is worth establishing early because it drives everything downstream: the size of the array that fits usefully, whether the design needs to spread across multiple planes, and whether module-level power electronics earn their cost.
Ask for the production estimate broken down by roof plane rather than as a single total. A design placing a meaningful share of the modules on a poor plane should be justified, and seeing the split is what lets you ask the question.
A newer roof is a genuine advantage here. It means the array is unlikely to need removing and reinstalling for a roof replacement inside its life, which is a cost older homes have to plan for.
Hardware choices for a coastal site
Leeward coastal Oahu is a salt-laden environment, and salt air is hard on metal over the twenty-five year horizon a solar system is sold on. Mounting hardware, fasteners and enclosures all sit outdoors for that whole period.
This is a specification question rather than a reason for concern. Ask what the racking and fastener materials are, what corrosion rating they carry, and whether the manufacturer warranty has any exclusion or reduced term for coastal or marine installations.
Ask the same about the inverter and any external enclosure, including where it will be mounted. An enclosure on a wall facing the prevailing salt-bearing wind is a different proposition from one in a sheltered position.
These are the questions that separate installers who work this coastline routinely from those who do not. A quick, specific answer is itself a useful signal about who you are dealing with.
Sizing when you cannot bank exports
Hawaii does not offer net metering to new customers. New projects join Smart Renewable Energy on the Export track, which provides export bill credits, or the Non-Export track, which permits no export at all.
Neither track banks surplus the way net metering did, so the old instinct of building large and letting the meter run backwards across the year does not apply. The value concentrates in electricity your household consumes directly, and in what a battery lets you shift into the evening.
That means the sizing conversation should start from your consumption pattern through a day rather than from your annual kilowatt hour total. Ask for the design to be shown against a daily profile, with production, consumption and, if included, battery state of charge on the same chart.
If a battery is in the design, Bring Your Own Device Plus pays $400 per kW of committed battery capacity with no maximum cap, doubled for low and moderate income households, in exchange for a five-year commitment and a two-hour daily export window you select.
Costing it out at Hawaii electricity prices
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 Kapolei receives no federal tax credit. Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements.
The state RETITC under HRS Section 235-12.5 remains at 35 percent of actual cost capped at $5,000 per system, where a residential system is 5 kW of total output capacity, so ask how many systems your installation comprises and how many Forms N-342 to expect.
BYOD+ remains available for a battery paired with rooftop solar, and the five earlier export programmes do not, being closed to new customers.
Then add the Oahu 2025 residential average of 40.54 cents per kWh, which is the largest term in the calculation. Ask any installer to rebuild the projection from those alone, with the production estimate broken out by roof plane.