The year is the accounting period, not the month
New Jersey provides full retail net metering, and the crediting works over the course of a year. The value is received either through directly offsetting the electricity that must be delivered by the grid, or through a credit applied by the electric distribution company after a month of net excess generation.
That annual framing suits a climate with real seasons. Long summer days produce more than a household uses, short winter ones produce less, and the arrangement is designed so that the surplus from one carries toward the other rather than being lost each month.
It also means a monthly bill is a poor way to judge whether a system is performing. Ask your installer for projected monthly figures across a full year so that you know what a normal January looks like, rather than being alarmed by one in isolation.
And it changes what you should ask about sizing. Ask your electric distribution company what limit applies to a residential system at your address and what determines it, and get the answer in writing before a design is finalised rather than after.
Sizing when generation itself is paid for
New Jersey is unusual in that the incentive pays on generation rather than on export. One SREC-II is created when a system generates 1,000 kilowatt hours of electricity, regardless of whether that electricity was used at home or sent to the grid.
In most states the sizing question turns on how much you consume yourself, because exports are worth less than retail. Here, full retail net metering plus an incentive paid on generation means the usual penalty for producing more than you consume is much smaller.
That makes the sizing question genuinely different, and it makes the limit set by your utility and by the programme rules more important than the usual self-consumption arithmetic. Ask what those limits are before assuming a larger system is simply better.
Ask for models at two or three sizes with both revenue streams shown separately for each. Seeing where the return stops improving with size, and why, is the clearest way to make this decision rather than accepting a single proposal.
What to interrogate in the projection
Because the incentive pays on generation, the production estimate drives both revenue streams at once. An optimistic production number inflates the result twice over, which makes it the single most important assumption to test.
Ask whether the estimate was modelled for your specific roof, orientation and shading rather than derived from a regional average, and ask to see monthly figures rather than an annual total. Then ask for a shading assessment covering the full year rather than the hour of the site visit.
Ask what incentive rate the projection applies and for how many years. The rate is set by the Board of Public Utilities rather than traded on a market, and the incentive runs for a term of 15 years, so a longer projection has to show what happens in year sixteen.
Finally, ask to see the figures with the incentive removed entirely. That is your floor, the value of the system on bill savings alone, and it tells you how much of the case depends on income that has an end date.
Two exemptions, and neither one happens by itself
New Jersey exempts solar energy equipment from state sales tax, but the exemption has a procedure and it happens at purchase. Under N.J.A.C. 18:24-26.4 the purchaser must issue to the seller an Exempt Use Certificate, Form ST-4, or other approved form, indicating on its face that the purchase qualifies for exemption as a solar energy system, with the installation property address inserted.
Ask your installer how that is handled and confirm the certificate was issued rather than assuming the price you were quoted already reflects it. It goes to the seller as part of the transaction, not to the state on a return later.
The property tax exemption is separate. Qualifying renewable energy systems are exempt from real property taxation under N.J.S.A. 54:4-3.113a to g, but Form CRES, the Certification of Renewable Energy System, must be filed with your local municipal tax assessor, and the system must be certified by the local construction code official.
The annual exemption is the difference between the total assessed value of the property before and after the system has been installed. Nobody files Form CRES for you by default, so ask whether your installer assists and put it on your own list either way. Requirements vary between municipalities, so a short call to your own assessor asking what they need is worth more than any general guidance.