Historic review comes before everything else
Portsmouth has substantial historic areas with design review, and if your property falls within one, that approval sits in front of the rest of the project rather than alongside it.
Ask early what review applies to your specific address, what it requires, and how long it typically takes. Ask your installer how many Portsmouth historic-district approvals they have actually completed.
If a less visible placement is required, ask your installer to model both options and give you the annual production difference in writing before you agree to anything.
That number matters more than it appears, because a placement that costs production costs it every year for twenty-five years, while the aesthetic question is settled once.
Salt air is a specification question
Coastal New Hampshire is a salt-laden environment and salt is hard on metal. Racking, fasteners and enclosures sit outdoors for the whole life of the system.
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 facing the prevailing salt-bearing wind is a different proposition from one in a sheltered position.
These questions separate installers who work this coastline routinely from those who do not, and a quick specific answer is itself a useful signal.
Storms, outages and what solar does not do
Coastal storms bring the power down here, sometimes for days. That makes resilience a legitimate reason to consider storage, separate from any savings argument.
Solar alone will not help. A standard grid-tied inverter disconnects when the grid goes down, for line worker safety, so an array without a battery and the right switching arrangement is inert during an outage.
Ask which circuits would be backed up and for how long under a realistic winter load. The answer should be a list of circuits rather than a reassurance, and it should include whatever your heating system needs.
Eversource has offered a residential battery incentive in New Hampshire, reported at $230 per kWh with a $3,000 cap. Confirm the current terms directly with Eversource rather than relying on a quote.
The pieces that remain, kept separate
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, and SB 303 repealed the state rebate in 2024, so there is no cash or tax incentive at either level for a cash or loan purchase.
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 Net Metering 2.0 at the partial credit rate, the RSA 72:62 property tax exemption if Portsmouth has adopted it, which is a question for the city assessing office, and no sales tax on the equipment.
Then add the electricity you stop buying at roughly 24 to 27 cents per kWh, and if a historic-district placement is in question, the production difference between the two options in writing.