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603 Solar

In a world where there are so many solar companies to choose from, how do you make the right choice? Three words come to mind: transparency, accuracy, and integrity. At 603 Solar we take an educational approach to solar as there are many factors that go into designing a system that is tailored to your exact needs. Each home uses a different amount of electricity and has different concerns regarding shading and orientation. We make the entire process simple and straightforward from conception to commissioning, while providing the best possible customer service!

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603 Solar was established in The fall of 2018 and since has helped nearly 1,000 home or business owners make the switch to solar. The company was formed by Zachary Haithcock, Sean Carlson and Scot Johnson after collectively witnessing a lot of deceit and dishonesty in the industry. With relatively little regulation solar companies were taking advantage of more and more home and business owners - something had to be done. 603 Solar was created with one purpose in mind: educating home and business owners on the benefits of solar energy, in the most transparent way possible, and assisting them in their solar panel installation so they can receive the best return on their investment. In 2023, 603 Solar was named the # 1 Solar Company by both the "Best of the 603" magazine and the "Best of the Seacoast" community choice awards.
Year Established
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Reasons Why You Should Work With Us
  1. Highly rated local business

  2. Transparent educational approach to solar

  3. System production guarantee

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Elite installers earn top ratings from customers, endorsements from vendors, and win customers more frequently than their peers.

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We offer turnkey solar design and installation services for residential and commercial properties. This includes everything from conception to commissioning: design of the system, engineering, permitting / interconnection, installation / inspection and finally commissioning / post install support. We strive to make the process as transparent and easy as possible!

Services Offered

  • Installation

In a few short words - our team is lean and mean. While we embrace the "small, local company" vibe, we boast "big company" results. We are one of the fastest growing and reputable local companies in NH. Our team ranges from college graduates just getting their foot in the renewable energy industry, to 10+ year veterans who have seen it all! No matter how big we grow our team will always embrace the small company vibe and put our clients first.

Associated financing companies

  • Vermont State Employees Credit Union

Workmanship Warranty

Contractor warrants all solar-related work for a period of twelve (12) years following completion. The system’s most critical components – the solar modules and inverters—are covered by 25-year performance warranties, which protect against component-related failure.


Electrical Corporation License (0594C) - Zachary Olster 15155


We carry both General Liability as well as Workers Comp insurance. Copies of both can be furnished at your request.


FAA Remote Pilot (Drone)

Industry Certifications

Manufacturer Certifications

  • Gold Installer

What Customers Are Saying

11 reviews
Average Rating 11 review(s)
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Very Good Experience

Jeff Cantara and 603 installed Enphase inverters and Q Cell 425 watt panels for me. Excellent, painless, reasonable price. John

Posted by johnlumbard on Mar 26, 2024
Couldn't be happier!

603 Solar has been great. Our "salesman" Jeff was very informative and honest. He actually talked us out of spending additional money on "add-ons" that a previous solar company pushed us to do. Jeff also made several revisions to our design at our request so we could get things "just right". 603 kept us informed throughout the entire process, their installers showed up when they said they would and didn't leave any mess/debris behind when they were finished. The entire process from our initial meeting with Jeff to when we were able to "turn on" our new net meter took less than 2 months.. and part of that time was waiting for permits and the utility company.

Posted by jeremy on Mar 18, 2024
603 Solar - Talk to them before making your decision

I was very happy working with Jeff Cantera at 603 Solar. He has a vast amount of knowledge and loves what he does. He can be very technical but also answers basic questions. We had very pushy solar company put in connection application before we had all our questions answered. Jeff and 603 solar to the rescue. Jeff answered our questions and helped us navigate the process with town and Eversource. 603 even helped us remove the other connection application. Very good experience with Jeff and everyone at 603 solar.

Posted by kclarkejr on Mar 14, 2024
Smooth Process Start to Finish

Working with 603 Solar and, in particular, Jeff Cantara was so easy and straight forward. After not having our messages returned by other local solar companies we found 603 Solar and we are glad we did. Our initial phone call was answered and Jeff Cantera was assigned as our project lead. Jeff came to our home and walked us through the process and put our project on a schedule that exceeded our expectations. From our initial contact in October, 2023, to a 100% completion in early February, 2024, our array is up and running and we appreciate the consistent attention we recieved and we are delighted with the results! Thank you, Jeff Cantara and 603 Solar!

Posted by dandc100 on Feb 09, 2024
603 Solar - The best in New Hampshire, hands down.

I’ll make the long story short: If your phone number starts with "603", and you want a solar system, then call 603 Solar. They are as good as advertised, and work hard to earn the stellar ratings you see online. They are the real deal.   Here’s the long story….. For background information: The solar system installed is a 12kw Net-metered grid-tied rooftop system on the Seacoast of NH. Installed the last week of November 2023.   Pre-Installation: I called 603 Solar after finding them in a Google search, so they were not referred nor do I have any pre-existing relationship with them. Had a solid conversation with their office manager, Marian, and was set up for an on-site evaluation with their designer, Jeff Cantara. Jeff and I met at my home just 3 days later. Here’s where things started to go very right: there are designers that design, and there are designers that KNOW their stuff cold and share what they know. Jeff is the latter type. What was supposed to be a 30 minute conversation turned into 90 minutes, delving into design ideas, efficiency discussions, a sidebar about bicycles, EV’s and their charging, even how we could run the cabling to keep it as “clean” as possible. He came prepared with drawing ideas, too, clearly having done his homework before our meeting. Personable, extremely knowledgeable, and good with dogs, too, Jeff was outstanding to work with.   Design: Jeff send the proposed design over literally the next day. The design was great. We did get quotes from 2 of their competitors; 603’s quote was in the middle of the other two. We signed the contract that week, and 603 got to work with permits. I heard from a lot of their group, including Erin and Sean, during this process, keeping us informed of everything that was going on along the way. Installation: The day after Unitil gave their approval, Marian was on the phone with me to schedule an install date.  Happily, their installer, Zach Olster, and his crew had an opening just two weeks later. A few days before the install, all of the equipment arrived on pallets, and was left exactly where I asked them to leave it in the driveway. Zach and his team showed up right on time: they said they’d be here at 8am, it was 7:59am when they pulled into the driveway. Zach said they’d have it done in one day, as promised, and they got to work. And work they did: clean, fast, friendly. They did a fantastic job. Everything is aligned spot-on, square, right, and tight. Solid workmanship. They clearly take pride in a job well done. They were cleaned up and gone by 5pm with not so much as a scrap of plastic left behind. Jeff called me midway though the day just to check on how the installation was going, too. Commissioning: 603 Solar had town inspection the next day! The system passed inspection with zero comments. 603 submitted the paperwork to Unitil for the tie in then; Unitil approved it about a week later and swapped out our meter to a net-meter the week afterward. Again, the day after the meter was installed and the system came online, Jeff was on the phone with me to set up a time to walk us though the Enphase app. 603 also submitted all of the paperwork to earn our SREC credits; I just signed. I realize that you may be thinking “Yeah, but the person writing this review only wrote the good stuff, they glossed over the bad!”. Here’s why there’s no bad written here: because there was no bad. Literally every interaction I had, every call, every everything, went well. It was more like working with friends than working with a company. That’s a strange place for me to be, as I’ve thrown contractors out of my home though the years. I went into this with a “here we go again” mindset, but came away wanting to invite them over for burgers on the grill this summer.   603 Solar is based right here in Exeter, they live and work in the communities we live in, and clearly wish to deliver a superior product and service and stand behind their work every step of the way. They’re our neighbors. They have earned every positive word of this review.

Posted by chris on Feb 06, 2024
Going Solar...

Great experience, Jeff Cantara was very knowledgeable and answered all my questions in simple ways. Schedule and installation happened exactly when it was promised. Installation team was punctual and very professional, site was maintained clean during the installation and by the end it was like they were never there.

Posted by elfgfs on Feb 06, 2024



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