Choosing a solar system for your home



Typically, most systems are designed to cover at least 80% of the electrical needs of your household. Most incentives require this 80% design requirement. During our site visit, our solar sales consultant collects data that the engineer will use to design a suitable system.

  • Your electrical bill tells us how much monthly power or capacity is used by the various appliances and their users.

  • Your exact location based on pinpoint GPS coordinates is retrieved. Your location is evaluated with sun chart to determine solar access.

  • Your skyline helps us determine shading considerations. See picture to the right.

  • Your roof's tilt and azimuth angle will help us determine the size of your system.

The size of your system is determined by the size of your roof and your budget. To garner the many incentives, we are obligated to cover at least 80% of your electrical bill. But designing a system that covers 100% or 150% of your electrical needs is also a possibility. Generally, people opt for a mixed system - one that relies on both the electrical grid and its solar panels.

Typical System Sizes

Most residential solar systems average 5kw. This average system would cover 80% of the household's electrical needs.

Boston Solar Installs (kW) by Month

Solar Insolation in Boston


This table shows the average insolation in the city of Boston per month. The higher KW per square meter in the summer reflect the higher insolation in those months.

Location Considerations


Shading on solar arrays can have a serious impact on efficiency. Surrounding trees, chimneys, plumbing vents, nearby structures need to be accounted for in the system installation and sizing.











Roof Orientation

The perfect solar roof points due south.  Very rarely does a perfect solar roof present itself, obviously. Generally speaking, only one side of any roof is ample for solar generation even when pointing well off of due south.


Roof Structure

Roofs with many valleys and dormers are less suited to optimal solar generation. Some houses with very complex roof structures might not be suitable at all for a solar array.


Sunlight Considerations

Most people don't think of Massachusetts as a sunny state appropriate for solar installations - places like Arizona, Florida and California first come up. But the world leader in solar installations is Germany which has 1/2 the sun exposure of Massachusetts and New England in general.

Furthermore, Massachusetts' electrical rates are amongst the highest in the United States. Coupled with generous state incentives, Massachusetts solar installations make strong financial sense.

The sunlight availability chart below shows the average hours of DNI (Direct Normal Irradiance).