Electricity Generation

This peak capacity is a measure of the electricity generated when the sun is shining brightly and its rays are hitting the panels at a 90 degree angle. Since this occurs just twice a year as the sun is at the optimal angle over the horizon, PV arrays generate less than their peak most of the time. Of course when the sun is not shining they are not generating at all.

Using a rule of thumb that PV panels generate the equivalent of their rated capacity for 14% of the hours in a year, a 25 kW array should generate about 30,000 kW hours per year.

Since the school's electricity usage is about 220,000 kW hours per year, this additional array will supply about 15% of the school's electricity needs.

Why 25 kW for the array size?

Massachusetts has a rebate program for state residents, businesses, and towns. For systems up to 25 kW, towns can get a rebate of $4.25 per installed watt. For systems over 25 kW and less than 100 kW the rebate is $0.25 per watt less. The Truro Energy Committee thought that sizing the project to maximize the rebate would be a good starting point.

How much will this cost to install?

The cost of a system of this size is typically under $8 per watt installed cost. A rebate of $4.25 per watt covers more than half the cost. The town's cost after rebate should be under $3.00 per watt. For a 25 kW system this amounts to approximately $70,000 one time cost.

Will this save the Town of Truro money?

Yes, the electric bill should be reduced by about $7,000 per year on the average. But like most investments, there is a payback period for the initial investment. In this case the payback is about 10 years, assuming a 5% annual increase in electricity prices. The savings in the school's electricity bill will pay for the system in that time. After that, all the savings in the electrical bill will be a 100% savings for the town.

Where do we go from here?

The project will be presented for approval as Warrant Article 9 at the annual town meeting on April 28. It has already undergone review by the Town Administrator, the School Board, the Finance Committee and the Board of Selectmen and all have unanimously voted in support of the project.

Who will be installing the new system?

A competitive bidding process will be conducted by the town as is typical of projects like this. The selected vendor will be responsible for the installation.

How can I find out more?

By emailing your questions to truroenergy@aol.com. The Truro Energy Committee will endeavor to answer all inquiries.