This was very hard to find. It is actually under Credits: Business related non-refundable credits

There is a drop down menu for Solar and Wind. Then you enter the credit available to you and credit you are taking this year. You do not need a certificate number.

These are the qualifications for this credit:

The Solar and Wind Energy Credit is available to owners or tenants of residential property who install a renewable energy source such as a solar hot water system.

The credit is 15% of the cost, including installation, of the renewable energy source. The credit cannot exceed $1,000. If you moved during the year, you may take the $1,000 for each of your principal residences

The residential property must be your principal residence. For example, a summer home does not qualify.

The following must all be true to qualify:
 - you must be the first one to use the energy source item
 - it must be expected to last five years
 - it must meet the performance and quality standards set by the Commissioner of Revenue

Complete Massachusetts instructions (page 27):

https://www.mass.gov/files/documents/2019/01/16/dor-2018-inc-form-1-inst.pdf