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Solar Installer GuildUnited States · independent

A1 Sun Inc.

Solar energy company · Berkeley, CA

What the listing shows you

4.6★

11 Google reviews

What it doesn’t

9%

rated 1–2★

typical in the Oakland area, 0%

Newest review held

Aug 2026

newest held review this month

Google's rating breakdown · all 11 reviews

Rated 1–2★
9%
typical in the Oakland area, 0%
Posted an update
—
we saw no owner post, which is not the same as none existing
Replies to reviewers
9%
of the 11 reviews we hold

Its one and two star share is 9 points above the typical installer in the Oakland area. Across California, 450 of the 1,529 installers whose breakdown Google has published carry a higher share than this one.

The percentages are Google’s own arithmetic over every review it holds, not a sample we assembled. Separately we hold 11 review texts for this company, quoted below. Google publishes review ages rather than dates, so every date here is approximate.

Every company we hold in the Oakland area, on one axis

0% rated 1–2★10%

Each mark is one company we hold in the Oakland area whose Google breakdown has been read, placed by its share of one and two star reviews. A1 Sun Inc. is the red one. The amber line is the middle of that set, which includes suppliers and maintenance businesses as well as installers.

What reviewers said

  • 1★ · around August 2025 · the company replied

    I just got off the phone with "Ferrar", Service Manager, about an Enphase warranty repair. A1 Sun , the Enphase Platinum contracted installer in Berkeley, will not effectuate Enphase labor/product warranty repairs per what Enphase contracts. Their estimated surcharge for an estimate to determine what repairs are needed is a minimum of $550 plus $200 per hour after two hours. In my case where the system electrical defects are known, to replace out an IQ Controller 3, the time to do this will be "a half day", and the total cost in addition to the, apparently, $200 Enphase offers as compensation

  • 5★ · around August 2026

    We contracted with A1Sun for our solar install with battery and couldn’t be more pleased with their service and professionalism. We had quotes from at least 4 other companies but A1 Sun had the most comprehensive and best tailored system for us. They handled every step of the process with clear communication. Super impressed with this group, would recommend to any looking for solar/battery solutions.

  • 5★ · around July 2026

    Thanks to everyone at A1 Sun for installing a great system in my home. They advocated for the best pricing, gave me a clear timeline and did all the appropriate permiting and follow-up. Everyone on the time was knowledgeable and skilled. I'm so pleased to have worked with this well-established, local business doing good things for the world.

  • 5★ · around April 2026

    A1 Sun is a true local gem, committed not only to providing excellent project management and customer service, but also to hiring, fairly compensating, and retaining a skilled and dedicated staff in Berkeley. The Giustino family's lifelong passion for solar, including an enthusiasm for education as well as installation, has clearly infused the ongoing enterprise with a cohesive sense of collaboration and commitment. I had a VERY complex design and installation project, requiring careful and consistent long term scheduling and coordination under various tight PGE deadlines. A1 Sun came through

Reviewer names are not published here. Negative reviews are shown first because they are the ones a listing hides, not because they are more representative.

What reviewers keep mentioning

  • solar installation 6
  • system 6
  • project 3
  • contracted 3
  • design 3
  • management 2
  • local business 2
  • communication 2
  • pricing 2
  • battery backup 2

Topics Google derives from the review text, with how often each appears. A frequent topic is not a good one: “price” turns up in praise and in complaints alike.

What the company says about itself

Taken from its own website. We have not checked any of it, and a sentence on a website is not evidence.

  • Warranty

    “Most solar panels are under warranty for 25 years or more – but will…”

  • Established

    “design and installation company. Since 2007 we have been helping Bay Area…”

  • Years in business

    “Larry Giustino began working in solar more than 50 years ago, and has been a part of every…”

Its website also mentions free estimate, family owned and licence number, but not in a sentence we can quote cleanly.

When they say they are open

Sunday
Closed
Monday
7:30 AM to 4 PM
Tuesday
7:30 AM to 4 PM
Wednesday
7:30 AM to 4 PM
Thursday
7:30 AM to 4 PM
Friday
7:30 AM to 4 PM
Saturday
Closed

As Google published them when we last read the listing, not a live check. Ring before you drive anywhere.

Who Google shows alongside them

Google’s own “people also viewed” set, in Google’s order. It is Google’s comparison, not ours.

The ones without a link have no page here, either because Google does not categorise them as solar businesses or because we could not match the name to a listing with confidence.

Other installers around Oakland

1–2★3★4★5★gauge 0–20%typical here, 0%

Ordered by how much we can tell you about each, which is not an order of quality. We do not know which of these is better and would not say if we did.

What we don't know

  • The date above is the newest review we hold, which is not necessarily the newest that exists — we hold a large share of Google's reviews, not all of them.
  • We do not verify licences, insurance or bonding. Nothing here has been checked against a state licensing board.
  • We cannot tell you what an installation costs, and we hold nothing about the equipment they fit.

Something wrong here? Tell us and a person will read it.

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