Check out this guide for a deeper dive into Solar PV: MassCEC Homeowners guide for Solar Power.

FAQ

• How does solar power work? Solar electric systems, also known as solar photovoltaics or solar PV, convert sunlight into electrical energy through an array of solar panels that connect to a building’s electrical system or directly to the electrical grid. The Massachusetts Clean Energy Center (MassCEC) has some good background information on this here. 
• How do I know if my home is good for solar? You can view your roof on Google Maps (click on the Earth box and enter your address) to get a sense for its orientation and potential shading from trees. South-facing roofs with little shade are best, but east and west-facing roofs work well too as long as there is little shade. Ideal roofs have long expanses of open areas but panels can be placed on smaller areas as well. Any installer you contact should be able to tell you on the phone if your roof is a good candidate. Some installers only want to work on the best roofs, but ultimately let it be up to you to decide if you want solar or not. In Wayland, we have homeowners who went ahead even though their roofs would have been declined by some installers.
• What if my roof is old? Should I replace it before installing solar panels? 15 years is about the dividing line between installing panels on the current roof and replacing the roof and then installing panels. If you install the panels on the existing roof, the panels will protect the part of the roof on which they are installed. You can have the panels taken off and reinstalled when you decide to re-roof. 
• Do I have to maintain my solar system? Generally the panels will sit up on the roof out of sight and out of mind, powering your home, even on cloudy days. There are no maintenance contracts to buy and New England weather will keep the panels pretty clean.
• What happens when it snows? Snow will pile up on solar panels, but the sun’s energy soon melts the bottom layer next to the panels and the snow will come sliding down quickly. Snow guards are available to protect people and plants under the panels.
• What about critters? If you frequently see squirrels on your roof, you can add critter guards to prevent them from damaging your system wiring.
• How do I get paid for the electricity my system sends to the electric grid? On the days that your system makes more electricity than you consume, your meter will run backward. This is called net-metering. If you underproduce/overconsume over the billing period, Eversource or National Grid will charge you for the total amount of kWhs (kilowatt-hours) for the excess used kWhs at the full residential electricity rate. If your system has overproduced, Eversource or National Grid will not pay you back at the end of the billing period. Instead, they will put those kwHs in reserve. You can use up that credit during the darker months, when you won’t produce as much. If at the end of a full year you still have a credit, you can “Schedule Z” to any other electricity user in your load-zone. You can ask that off taker for $$, or donate it. More info here.
• How big should my solar system be? Since selling excess electricity isn’t that straightforward (yet!), it makes sense to have a system that is properly “sized” just to cover your electric bill. However, you may decide to install a bigger solar system with future added electricity use in mind, like an electric car, or air-source heat pumps for heating and cooling.
• What is the process of going solar? Generally a solar installer will ask for a copy of your electric bill and will prepare a proposed layout and financial estimate based on that and your roof space. Some parts of your roof may get more sun than others; you can change the layout to meet your needs. Once you have approved the design and signed off on the financials, the solar installer will handle the installation, checking roof structural support, pulling permits, obtaining equipment and scheduling the work. It may be a month or two until installation. Actual installation usually takes 2 days – electrical work and roof racking on day 1 and panel installation on day 2. After building and electrical inspections, Eversource or National Grid will install a new meter and give you approval to power up your system.
• What happens when the grid is down? If you’re looking to keep powering your home when the grid is down, you’ll have to add a backup battery system, which is an expensive option. Otherwise, if there is a power outage, your electricity generation will be disabled during the power outage.