Why the rate assumption carries the quote
Savings from solar are production multiplied by what a kilowatt hour is worth. With the incentive column empty, there is nothing else in the calculation to absorb an error in either term.
New Hampshire rates are high but they are also reported inconsistently. Figures around 24, 26 and 27 cents per kWh all appear depending on the source and the month, and utility rates differ between Eversource, Unitil and Liberty.
So ask which rate the projection used and where the figure came from, then check it against a recent bill of your own. That takes a minute and it validates the largest input in the model.
Ask whether the figure is all-in, including supply, transmission and distribution, or only the supply portion. A model using supply alone will badly understate savings; one applying an all-in rate to exported kilowatt hours will overstate them, because exports only receive 25 percent of distribution.
The charges that do not fall
Fixed monthly charges do not decrease when your consumption does. A household that halves its energy purchase does not halve its bill, because part of the bill was never about kilowatt hours.
A projection that models savings as a percentage of the current bill rather than as avoided kilowatt hours will overstate the result, sometimes substantially.
Ask what fixed monthly charges apply on your utility and whether the projection accounted for them. Ask also whether any charge changes for a net metering customer.
This matters more in a state where the case rests entirely on avoided cost, because there is no incentive line to absorb the discrepancy.
The escalation assumption to interrogate
Most long-run projections assume electricity prices rise over the term, and in New England that has generally been true. It is also a very powerful assumption, because a compounding escalator across twenty-five years can generate most of the headline savings on its own.
Ask what annual escalation rate the model applied and what it was based on. A modest figure grounded in regional history is defensible; a large round number is not.
Ask to see the projection at zero escalation alongside the main one. If the case still works with no assumed increase, it is a robust case rather than a bet.
That test is worth more in New Hampshire than almost anywhere, because with no incentives left the escalator is the only other lever a quote can pull to make the numbers look better.
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.
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 crediting exports at 100 percent of supply, 100 percent of transmission and 25 percent of distribution, the RSA 72:62 property tax exemption where adopted, and no sales tax.
Then add the electricity you stop buying, at a rate taken from your own bill, with fixed charges accounted for and the escalation assumption stated and stress-tested at zero.