Hotstart Acquires GTS

Jan 3, 2023

Spokane, Wash. – Hotstart has acquired GEO-THERMAL SYSTEMS, INC. (GTS) effective December 22, 2022. The acquisition brings to Hotstart’s thermal management product portfolio high efficiency heating systems using proven heat pump technology to maintain standby generators installed in the Americas. The heating systems provide up to 75% energy savings while adding a level of backup redundancy with the existing engine heaters which are often Hotstart systems.

GTS was founded in 1991 by Jim Whittlesey, a former Caterpillar employee, who saw an opportunity to improve the traditional engine heating process for standby generators. By adding a modified air-source heat pump to the existing block heater installation, a more energy efficient solution was possible. GTS supplied this solution to customers during 30 years of operation. Thousands of heating systems have been installed on generators in facilities including commercial, industrial, government, military, universities, airports, hospitals, and data centers, saving end users significant energy and money.  

Patrick Whittlesey, former GTS VP of Operations, joins Hotstart as Market Manager – High Efficiency Generator Heating - Americas. Patrick will be responsible for sales of heating systems throughout North, Central, and South America. Jim Whittlesey will serve as advisor to Hotstart in a consultant role.

“I’m excited to have the GTS team join Hotstart,” said Terry Judge, CEO of Hotstart. “Their generator experience and strong customer relationships align well with our 80 years of engine heating expertise. We look forward to providing this technology to customers that seek energy savings and lower carbon footprints.”  

“We are thrilled to be part of the Hotstart team,” said Patrick Whittlesey. “Over the years, we’ve seen Hotstart products on numerous emergency generators in the field. It’s apparent they are the leader in the industry, which made joining them an easy decision to make.” 


Terry Judge welcomes Patrick Whittlesey in joining Hotstart as part of the acquisition of GTS.

The GTS product line will now be offered as Hotstart High Efficiency (HE) Heating Systems. Information on HE Heating Systems can be found at Customers with existing GTS units can contact Hotstart Customer Service at 509-536-8660 for service and support. New customer inquiries can be directed to

Hotstart GTS Acquisition