Premier Heating, Air & Plumbing from a Family-Run New Hampshire Business

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HVAC Contractor & Plumber Services For Homes & Businesses

Heating Services

Cooling Services

Plumbing Services

Water Quality Services

Indoor Air Quality Services

We're Local - Since 1987

GSMS is a second-generation family business dedicated to doing things the right way

GSMS is a second-generation, family-owned business that answers to our neighbors, not a board of directors. We’ve grown one referral at a time by treating every Client like family and every home like our own. Our mission is simple: we want to be the name you trust to take care of you and your home.

Get to Know Us

The Specialist Standard

Specialists, not technicians

We send Specialists, not technicians. Each one takes ownership of your whole system, not just the part that broke.

The Great Service promise

Affordable pricing, 5-star service, and pride in our work. If you’re not satisfied, we’ll make it right. It’s how we’ve worked since 1987.

The independent alternative

While large out-of-state firms buy up local shops, GSMS stays family-owned and answers to our neighbors, not a board of directors.

Built on our values

Every visit is guided by four values: grateful daily, service comes first, make it matter, and success is teamwork.

The GSMS Learning Center

We have been keeping New Hampshire homes comfortable since 1987, and we love sharing what we know. Our Specialists break down heating, cooling, plumbing, and indoor air quality in plain language, so you can make confident decisions about your home.

How to fix a Lennox thermostat A2L sensor fault code

Quick answer: A Lennox thermostat A2L sensor fault code, often shown as Alarm ID 163, means the system's Refrigerant Detection System (RDS) sensed a change...

08/21/26 Read More

Why Lennox Healthy Climate Uses UVC, Not Standard UV Light

If you've shopped around for a UV air purifier for your Manchester, NH home, you've probably noticed the listings don't say much. A lot of...

08/13/26 Read More

Why Mini-splits and Boilers Can’t Support Whole-Home Air Quality Add-ons

If you're running a ductless mini-split system or heating with a boiler, whole-home humidifiers and UV air purifiers are worth understanding before you shop for...

08/07/26 Read More

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Service with a local heart.

We believe a local business should be a pillar of the community. That’s why a portion of every service call we complete goes directly to a local NH non-profit through our We Local initiative.

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Since 1987

Excellence Defines GSMS

Comprehensive, Expert care for Every Room

Let's Make Home Enjoyable Again.

Total home protection, rewards, discounts, and smart monitoring. It’s all yours when you’re in the club.

Join the Club

Serving New Hampshire

No matter where you call home in New Hampshire, GSMS is here to ensure it remains a haven of comfort throughout the seasons. We work all across NH to deliver great service exactly where you need it.

Our Service Area