Stem

An Energy Storage System (ESS) is a stationary battery that stores electrical energy and discharges it as needed for a building/facility. An ESS may be charged and discharged strategically to lower electricity demand during different times of day to reduce customer energy bills. It can also be used to provide backup power in case of a power outage.

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Stem

Stem is one of the leading behind the meter energy storage providers, operating “the world’s largest digitally connected energy storage network.” They pride themselves on their artificial intelligence energy management software, Athena, to operate their systems efficiently. For more information on Engie’s energy storage offerings, visit their website at https://www.stem.com/solutions/energy-storage/.

Hub Highlights:

182 SGIP projects approved since 2017
Installation locations/configurations: Outdoor - roof mount, parking garage, or freestanding

Last Edited on: 06/05/2023

Data Source	All info is directly from providers unless otherwise specified
Number of approved SGIP projects since 2017	182
Grid service capabilities	Demand charge management Time-of-use (TOU) arbitrage Utility demand response programs Backup power Frequency regulation
Financing or ownership structures offered to customers	N/A
Who is responsible for performing maintenance?	Outside service provider and/or customer
Resiliency/integration features included with the ESS	N/A
Certifications and protocols held	N/A
Alarms included and who is alerted	Fire alarms - customer and provider Gas leak detection - N/A Theft alarm - N/A System outage - customer and provider
System benefits reported to customers	Environmental and financial benefits reported monthly. Customers may access reports through their online account.
Installation locations/configurations	Outdoor - Roof Mount Outdoor - Parking Garage Outdoor - Freestanding

Due to the nature of behind the meter energy storage systems (high cost and long timeframe for installation), the evaluation team did not conduct lab-based performance evaluations. The "test procedures" document below explains the data that were collected and results can be found in the technical specs and user experience sections.

Last Edited on: 07/2023

Data Collection

The UC Davis ESS evaluation team surveyed individuals who applied for the SGIP incentive for installing Stem energy storage at their commercial facilities.

Sample Size

Scoring

A 5-point rating (1-5) for each subscale was calculated as the simple scores of the assessment metric subsections below. Higher scores (closer to 5) mean a better (estimated) user experience.

Installation

It was easy to schedule the installation; I was very satisfied with the speed of installation; Integrating the ESS with other onsite systems required a lot of our time and effort; Permitting the storage system required a lot of our time and effort; Provider took care of connecting the storage system to our building systems.

Performance

The ESS operates well; The ESS has had performance issues; The ESS is reliable; I am satisfied with the price of the ESS; I am satisfied with the financial benefits of the ESS; I am satisfied with the reports generated by the ESS; I wish the ESS provided more detailed information about its operations; I am satisfied with the remote safety features (e.g., fire alarm and system outage) of the ESS.

Maintenance

It is difficult to find a service provider that performs maintenance; I am satisfied with the frequency of maintenance requirements; I am satisfied with the cost of the maintenance requirements; I am satisfied with the level of effort required of our organization to adhere to the maintenance requirements; The ESS is easy to maintain; Maintenance requires special tools; Maintenance requires special training.

Usability

System Usability Scale (SUS): I found the system unnecessarily complex; I thought the system and service was easy to use; I think that I would need more technical support to be able to use the system and service; I found the various functions in this system and service were wll integrated; I though there was too much inconsistency in the system and service; I would imagine that most people in my role would learn to use this system and service very quickly; I found the system and service very cumbersome or awkward to use; I felt very confident using the system and service.

General Satisfaction

Overall, I am satisfied with the ESS; If my organization needed another energy storage system, I would select this one again; I would recommend the ESS to others; I am satisfied with the company's customer service.