1. Confirm the utility and the property
Start with the electricity bill for the meter that would serve the solar installation. Identify the distribution utility, the account holder, and whether you are discussing a private home, a shared building, or a common-area meter. Cambridge’s official sustainability dashboard identifies Eversource customers in the city. That establishes a local connection, not the utility or tariff for every reader. If your bill names Eversource as the distribution utility, use its Massachusetts interconnection guidance and ask it to confirm the application for your account.
For a shared roof, ask who has authority to approve the work and which meter would receive the generation. Before comparing proposals, write down your goals: lower purchased electricity, a future electric vehicle, or battery backup. Ask each installer to explain which goals its design addresses. Keep account numbers and personal documents out of general introductory emails.
2. Ask for a roof and electrical review
Treat these as questions for the people evaluating your property, not findings about your home. What is the roof’s remaining service life? Who checks the structure, attachment design, and weatherproofing? Will repairs happen before panels go up, and who is responsible if later roof work requires removing them? Ask for the proposed panel layout and an explanation of the shading assumptions, including nearby trees and buildings.
For the electrical review, ask whether the service equipment, panel, and proposed connection can accommodate the design. Does the proposal include any necessary upgrades, or leave them for a separate contractor? Who specifies the disconnects, equipment locations, and access arrangements? If a battery is included, ask which circuits it would support and under what operating conditions. Request written answers tied to the actual equipment and property, rather than accepting a general claim that a package fits every home.
3. Use Cambridge’s municipal permit process
For a Cambridge residential rooftop project, start with the Inspectional Services Department (ISD). The city provides a building-permit application specifically for solar and links to its online permitting portal. Its electrical-permit guidance separately requires a permit for work covered by the Massachusetts Electrical Code. Plan for both the solar building permit and the electrical permit; ask ISD and your contractor to confirm the documents and any additional approvals for your particular scope.
ISD lists building inspectors and an Electrical/Wiring Division with electrical inspectors. Ask which inspector handles each part of your project, who requests inspections, and how you receive the resulting records. Do not assume that an installer’s completion notice is an inspection record. Keep permit numbers, approved plans, inspection results, and any correction notices together so you can distinguish work completed from work accepted.
4. Keep the municipality and utility tracks separate
For a home in Somerville, Arlington, Belmont, Watertown, or Boston, use that municipality’s own inspectional services or building department. Cambridge’s application instructions do not establish the requirements elsewhere. The state’s standard building-permit guidance directs applicants to contact the municipality where the work will be done. Ask that office which solar permits, reviews, and inspections apply. Local submission details outside Cambridge have not been verified in this guide.
Municipal permits concern the building and electrical work. Utility interconnection is a separate approval track for connecting generation to the electricity network. Record both sets of milestones. A passed municipal inspection is not, by itself, permission to operate a grid-connected system. The diagram below separates responsibilities; it is not a promised schedule or a complete checklist for every design.
5. Follow the serving utility’s application and authorization
If your bill names Eversource, its Massachusetts application page directs applicants to PowerClerk to submit and track applications. The page offers Simplified and Expedited/Standard application routes. Ask Eversource which route applies to the proposed equipment and service configuration; do not choose a route from the word residential alone. Ask who submits the application, who receives requests for missing information, and how you can check its status.
The Eversource tariff linked from its current interconnection resources distinguishes municipal inspection and completion documentation from the company’s authorization. It requires Authorization to Interconnect before parallel operation. Ask your installer to provide the applicable completion and inspection documents, any required utility review or testing records, and the utility’s written authorization. A finished installation, an application receipt, or an inspection pass does not replace that authorization. For another utility, request its own current process. No project duration is promised here.
6. Ask how your account would be credited
The Massachusetts Department of Public Utilities (DPU) explains net metering through its guide and 220 CMR 18.00. Its guide describes a bill credit when net consumption is negative. That is a billing mechanism, not a promise that a proposed system qualifies or that your electricity bill disappears. Our review could access indexed DPU text but could not open the full state guide.
Ask the utility: Which net metering rules and tariff apply to my account and proposed system? Is an allocation or other approval needed? How are exported electricity and remaining charges treated? What changes if I add storage or use a different ownership arrangement? Request a written explanation and keep it with your proposal. Account-specific eligibility, credit treatment, and remaining charges are unverified here.
7. Use PVWatts to question assumptions
The National Laboratory of the Rockies (NLR) provides the PVWatts model at pvwatts.nlr.gov. Use it to explore estimated production with stated inputs, not as a roof survey or an installation approval. Its roof-area size estimator explicitly does not account for roof tilt, azimuth, or shading. That limitation concerns the size estimator; it does not mean the production model has no orientation inputs.
Ask an installer which system size, tilt, orientation, and loss assumptions it used, and how those compare with the property review. Keep modeled energy production separate from a savings estimate, which also needs verified billing assumptions. Review our incentives guide before relying on financing or program eligibility. For solar with batteries, ask for separate equipment and financing explanations; the Mass Save discussion there does not promise approval. Finish by collecting warranties, monitoring access, inspection records, and utility authorization rather than accepting a verbal handover.