A new way to save with reliable and resilient on-site generation



NextEra Energy Resources and Mainspring Energy offer a new way to achieve energy cost savings with an innovative, low-emissions technology.

Cost savings are achieved with the linear generator by offsetting both energy and demand charge savings. The linear generator offers low cost electricity because of its use of standard materials and manufacturing processes along with low maintenance costs. Once installed, the linear generator can be efficiently operated on a variety of fuels, including low cost natural gas or renewable biogas. When paired with a renewable energy resource such as solar, the linear generator is able to adjust its power output to prioritize and maximize the value of onsite renewable generation.

Resilient on-site power is a key offering of the linear generator. The linear generator has backup and black start capabilities, which allow it to isolate and operate during a grid shutdown or outage. This is instrumental in maintaining power assurance and resiliency, especially for facilities with sensitive operations and critical infrastructure.

Renewables pairing is easy with the linear generator due to its fast load-following capabilities. It is equipped with proprietary technology that allows it to track load simply and without added cost or impact to efficiency, making it a perfect complement to intermittent renewable energy generation. With near-zero NOx emissions, the linear generator enables the clean, firm solution to a more complete sustainability program.

Benefits of Mainspring

Low Cost

Standard materials and manufacturing processes, two moving parts for maintenance, and high efficiency fuel costs


Ensures continuous operation of isolated grids, reducing the need for backup generation

Fuel Flexible

Runs on natural gas, propane or biogas


Ability to quickly vary power output to meet building demand with fast start/stop capability

Near-zero NOx emissions

Low-temperature reaction without a flame

Utility-scale performance in the size of a parking space

Easy Installation – One Fuel Connection – One Electrical Connection 

Each 240 kW package contains two linear generator cores, operating in tandem

Mainspring Features


240 kW, net AC
480 V, 3 Phase, 60 Hz
NOx < 2.5 ppmvd
Sound < 70 dBA @ 6 ft
Load Tracking
Zero to Full Power

Natural Gas or Biogas
8-25 psig Inlet
No Water
20.5’ x 8.5’ x 9.5’
UL 2200 Package
UL 1741 SA Inverters
Remote Monitoring

About Mainspring

Mainspring was founded in 2010 by three Stanford engineers seeking a new approach to generating clean, resilient, affordable electricity. Their research into high-efficiency methods of converting fuel to electricity led to the founding of the company and the development and prototype of their first linear generator.

Today Mainspring brings together a diverse, talented team of individuals who share the vision to address the growing threat of climate change and the need for affordable electricity for all. The company’s executive team brings deep expertise from leading clean energy companies and is backed by top-tier venture, strategic, and financial investors.