We Are the Most Reliable Mechanical Contractor in New York City

We give our clients peace of mind. We do this by providing the most innovative services and solutions through our experienced team.

We are New York City’s premier provider of HVAC service, maintenance, and construction, as well as energy solutions. When you entrust us with your HVAC and energy service needs, you align with more than 1,700 companies who value Donnelly’s hallmark of direct owner access at every level. Our customized maintenance and service agreements are tailored to your company’s unique needs. They are specifically designed to ensure peak operating efficiency, minimize equipment downtime and eliminate the need for repeat visits.

Donnelly Mechanical provides a maintenance transition plan and team to reduce the risks inherent in change.

We understand the difficulty of changing maintenance vendors. Reducing the risks during these transitions saves time and makes it easier to make a switch if you’re unhappy with your current service provider. During the transition process, the Donnelly Transition Team familiarizes themselves with your building’s entire HVAC system. This ensures consistent, cost-effective service at every point of contact thereafter. All technicians undergo a rigorous training program that equips them to service and maintain systems with the utmost care and confidence.