Why the estimate drives everything here
Massachusetts credits exported solar through net metering at or near the retail or basic service rate, and the SMART incentive is paid on metered production. Production feeds both, so an over-optimistic number overstates your return twice rather than once.
Ask whether the estimate was modelled for your specific roof, orientation and shading rather than derived from a regional average. Ask to see monthly figures rather than an annual total, because the annual number hides the seasonal shape entirely.
Ask for a shading assessment covering the full year rather than the hour of the site visit. Bare trees in March and full canopy in July are different shading conditions on the same roof.
Ask what happens if actual production falls materially short of the estimate, and get that into the contract. An estimate that appears only in a sales presentation is not a commitment.
What winter does, in both directions
Snow on panels stops production while it sits, and how quickly an array clears depends on pitch, orientation and mounting. Ask how the proposed layout sheds, whether any roof features would trap snow against the array, and what the mounting is rated to carry as a load.
Cold itself helps, since panel efficiency falls as cell temperature rises. A cold bright winter day can be genuinely productive, so the seasonal picture is not simply worse in every respect.
Ask what snow assumptions sit behind your estimate. A model that ignores snow days will overstate the winter months, which are exactly the months a household most notices its electricity bill.
Ask about the roof underneath at the same time. Freeze and thaw cycling ages a covering faster than the calendar suggests, so ask for a condition assessment rather than an age estimate, and replace a covering near the end of its life before the array goes on.
What has to be in place for the incentive
SMART is provided to customers of Eversource, National Grid and Unitil. Customers of municipal light plants are not eligible, and Massachusetts has approximately 40 of them, so confirm eligibility before anything else.
For residential systems under 25 kW, payments last a fixed term of 10 years at a rate determined when you enrol and locked for the duration. Ask what the current residential rate is and get it in writing.
Payments are made directly by the utility via the same billing structure as net metering, and each month the utility reads the production meter. Confirm a production meter is included and reporting, and ask how you can verify that months later.
Ask what the projection assumes happens after year ten when SMART ends, and ask to see the figures with the incentive removed entirely. That is the floor the rest of the case sits on.
Three state benefits, and the federal one that ended
Under 830 CMR 62.6.1 an owner or tenant of a residential property who occupies it as their principal residence is allowed a solar and wind energy credit against personal income tax equal to fifteen percent of the net expenditure for renewable energy source property, or $1,000, whichever is less, claimed on Schedule EC. It being available to a tenant as well as an owner is unusual and worth knowing.
Massachusetts also provides a property tax exemption of 100 percent for 20 years for solar installations, so the improvement does not raise your property tax bill the way a renovation of similar cost would.
And equipment for a solar system used as a primary or auxiliary energy source in a principal residence is exempt from sales and use tax. Check that your quote reflects that rather than assuming, and ask your municipal assessor what if anything they need for the property tax exemption at your address.
On the federal side, the 30 percent Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase now receives no federal credit. Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements, so ask any such provider what they claim and what of that value reaches you, and confirm with a tax advisor.