(Note: Shortly after publishing this product review, GTM learned that JLM Energy had closed its doors and laid off employees. See our story here.)

The team at Cinnamon Solar and Spice Solar have conducted a series of hands-on reviews of commercially available residential battery storage systems.

Reviews are based on the installation and usage of each system using commercially available products and software, provided by manufacturers. The intent is to provide useful real-world experiences to installers, homeowners and manufacturers as behind-the-meter battery storage systems become more popular.

In this review, we tackle the JLM Energy Phazr MicroStorage unit. 

JLM Energy has taken a different approach to adding battery storage to PV systems. Rather than employing a central battery approach, its Phazr MicroStorage system uses a relatively small (495 to 990 watt-hour) battery that is designed to be installed on the roof underneath a solar panel, and connected between the DC solar panel and AC microinverter.

The battery and integrated electronics provide direct battery charging by the attached solar panel, and provide DC output to the microinverter when there is insufficient sunlight. As a result, the system is very modular, allowing customers to “get their feet wet” with a battery storage system and install a system that most closely meets their home’s energy-use profile.

Phazr batteries work with a wide range of 60- and 72-cell solar modules with power outputs from 264 watts up to 350 watts. Different Phazr models are required depending on the solar module output voltage.

The JLM Phazr is a DC-coupled design in which the battery charges directly from each connected solar panel. Phazr batteries work with any UL-1741 listed microinverter or DC power optimizer. The Phazr system in this review was installed and configured using Enphase IQ6+ microinverters. Since microinverters automatically stop working during a power outage, the current Phazr design does not provide backup power in the event of a power outage.

Here's our overall rating.

Batteries on a rooftop?

Because of relatively high temperatures, a rooftop is not the optimal location for a lithium-ion battery. Nevertheless, there are advantages to installing multiple lightweight batteries on a roof under the solar panels. Instead of a single very large and heavy battery taking up precious wall space, multiple smaller batteries are easier to install without requiring additional space — which is a problem for many residential battery installations. (Note that electrical codes require clearances from existing equipment, and there is limited available indoor and outdoor wall space in many homes.)

Keep in mind that 10 years ago the roof was not considered to be an appropriate location for module electronics. Enphase, SolarEdge and others proved that microinverters and optimizers can indeed be designed to function efficiently and reliably on a rooftop.

JLM conducted high-temperature (55 degrees Celsius) discharge performance tests in which the cells maintained over 95 percent of their original charge after four hours. Cells also maintained over 80 percent of their capacity for over 2,000 charge-discharge cycles. Although these laboratory tests are no substitute for a decade’s worth of real-world rooftop operations, we anticipate that small-scale battery storage systems such as the JLM Phazr can be designed and manufactured to be efficient and reliable on a rooftop.

New electric rates encourage battery systems

The popularity and economics of utility-scale solar farms have dramatically reduced the cost of electricity during peak sunlight periods, usually between 10 a.m. and 2 p.m. As a result, time-of-use electric rates during midday (now considered off-peak or partial peak) are much lower than rates in the afternoon and evening (now considered peak). A rooftop solar system without energy storage would send excess power back to the utility during these off-peak periods at lower rates. Without energy storage, during late afternoon and evening peak electricity periods when there is little or no solar generation, a typical solar customer would be paying their utility for peak electricity.

The modularity of the Phazr system is a big benefit to customers who do not want to sell power back to their utility when rates are low and purchase electricity when rates are high. A Phazr system can be sized to add just enough batteries to store excess midday power, and “self-consume” this power in the afternoon and evening. Additional Phazr batteries can be added as rates change or customers require more stored energy. The Phazr system has several configuration options to optimize the system’s operations for the wide range of net metering and grid interconnection requirements in the U.S.

Documentation, training and support

JLM Energy provides comprehensive and readable documentation for Phazr battery, mounting, networking gear and software. When needed, system sizing guidance is provided by a service representative. Sales staff provide training at regional solar and storage events, training with affiliated distributors, as well as customer-specific training. Its customer service representatives are available from 8 a.m. to 5 p.m. PST. Its website is here and the customer support number is 800-475-3960. 

Shipping and transportation

DOT hazmat training is required for all personnel handling lithium-ion battery systems that weigh more than 50 pounds. Since individual Phazr batteries range in weight from 13 to 23 pounds, the full range of these hazmat requirements do not apply. Phazr batteries can be shipped by FedEx and UPS with special labeling and handling requirements. Significantly, the relatively light weight of Phazr batteries makes them much easier to order, transport to the job site, and carry up a ladder (following safety procedures) to a rooftop. In general, no special mounting or structural engineering requirements will apply to Phazr batteries (unlike structural engineering that may be required for a 200-pound battery mounted to a wall).

Design and engineering

Most large residential lithium-ion batteries have capacities in the 10 to 13 kilowatt-hour range. Customers generally install one or two batteries, so there is not much design work that goes into system sizing. Basically, it’s a choice of one battery or two. 

The modularity of the Phazr design means that more thought is required to determine how much battery capacity is required. Customers who want to optimize their self-consumption of solar energy (without net metering) would select the number of batteries that would match the average daily output of their solar system, and then subtract their average daytime consumption. For example, if average daytime consumption is 10 kWh and PV output is 20 kWh, 10 kWh of battery storage would be needed to ensure that the value of this power is not lost (without net metering). This would equate to approximately 15 Phazr-8s (each of which has a capacity of 0.66 kwh). Determining the number of batteries needed for time-shifting of energy use is a bit more complicated since it depends on the cost and timing differences between midday partial/off-peak electric rates and afternoon/evening peak electric rates. 

With a weight of 17 pounds, or about 1 pound per square foot, the additional weight of the Phazr battery will have minimal impact on rooftop structural loads in most jurisdictions. This relatively light weight is also compatible with all but the lightest rooftop racking systems. JLM recommends spacing the Phazr no more than 48” from each roof mount to avoid torqueing the rail to which it is attached. 

Permitting for the Phazr system is like a standard PV panel and microinverter installation, plus whatever additional requirements that may apply by the jurisdiction for a rooftop battery storage installation. Since there are no additional AC or DC conductors with the Phazr system, additional Rapid Shutdown components are not required. Local utilities may require additional safety or set-point configuration changes so that the battery storage system meets their interconnection requirements. Finally, rebate administrators (such as the California Self-Generation Incentive Program) will often have additional application and operating characteristic requirements. 

Installation details

Test site conditions:

  • Commercial building with three-phase 208-volt service
  • Five 60-cell solar panels with Enphase IQ6+ microinverters 

JLM Energy designed its Phazr batteries to be installed on the racking system underneath each PV panel. For sloped roofs, JLM’s documentation indicates compatibility with Quickmount roof mounts (or equivalent) and IronRidge XR-100 rails (or equivalent) so that the Phazr can be attached directly to the racking using stainless steel hardware.

Plus and minus output wires from the PV panel are attached to the Phazr, the output wires from the Phazr are attached to the microinverter, and then the AC output of the microinverter is wired as with a typical microinverter system. Care is required to ensure that the PV panel and microinverter connections to the Phazr are done properly. Bonding is accomplished by connecting the Phazr’s factory-installed grounding lug to the array grounding system. For this test installation, instead of flush-mount racking, the system was installed on a flat roof using Spice Solar integrated racking and tilt legs mounted to ballasted 4x4” sleepers tilted at an angle of approximately 10 degrees. The Phazrs were attached directly to the panels with two bonded stainless steel L brackets.

Additional components include the Linez monitoring system, two Amplifi wireless mesh point boosters, Phazr Hub and Amplifi Router. (These networking and communications components are described in more detail below.) Non-JLM Energy electrical components include five microinverters, a rooftop junction box, microinverter combiner box and microinverter monitoring gateway. 

Monitoring, networking and communications

Perhaps the biggest challenge with battery storage systems relates to the additional monitoring, networking and communications requirements for these systems. Many standard PV systems include monitoring of the inverter, as well as individual panels (when equipped with optimizers or microinverters).  Battery systems also require monitoring of the battery’s operating condition and monitoring of the building’s electrical energy consumption. 

The Linez unit is used to monitor the building’s energy consumption. In this case, it was mounted on a junction box and connected via EMT to a nearby service panel with a two-pole, 15-amp breaker and four wires (L1, L2, neutral, ground). These conductors power the Linez unit and provide the proper reference voltage for monitoring. The first set of current transducers (CTs) was connected to the L1 and L2 output of the microinverter circuit so that the solar power generation could be monitored. The second set of CTs was attached to the incoming L1 and L2 in the service panel so that the net building power consumption could be monitored.

The Phazr system uses multiple components for networking. Although the process to connect these components is somewhat complicated, the communications worked effectively once everything was configured. The Phazr Hub (cube-size box) networks wirelessly with Linez and the Phazr batteries. To enhance the signal from the rooftop Phazr batteries, two Amplifi Mesh points were installed, one close to the Phazr Hub and once close to the roof.

Each Amplifi Mesh point is plugged into a standard outlet. The Amplifi Router (small rectangular box below the Phazr Hub) is connected to the building’s router with a standard CAT5 connection. These networking components are in addition to the networking for the microinverters themselves. Since there are multiple networking devices for the entire system that are operating 24/7, parasitic loads with the Phazr are likely to be higher compared to other battery storage systems. Unlike all the other roof-to-interior wireless monitoring we tested, the Phazr connection via the mesh network was the only system that worked wirelessly through the foil insulation below our commercial building’s roof.

Software and configuration

Configuration of the system was completed once the Phazr batteries, panels, microinverters, Linez monitoring and Phazr Hub were installed and powered up. JLM provides the Measurz Mobile App for the initial configuration. Once installed on a mobile device and logged in with installer credentials, the barcode identifying each Phazr battery is scanned. The Measurz app then completes the configuration, with assistance as needed by contacting JLM customer service to verify connectivity and proper operation of all components.

Once configuration of the system was completed with the Measurz mobile app, the performance of the system could be viewed remotely on a PC or cellphone, including total building consumption, solar production, self-consumption, power import from the utility, power export to the utility, battery status and historical data. JLM offers the ability to set electric rate profiles to establish optimal charge/discharge times so that customers can charge from PV or the grid when rates are low, and discharge the battery to the home when rates are high.

As with most other remote monitoring and battery systems, the first few Phazr system installations will take longer to configure. To date, all building power consumption systems we have tested use CTs that are often difficult or impossible to install on large L1 and L2 feeder conductors. Rogowski coils, along with a controller and power supply, are the best option we have identified (although they are not currently supported by most manufacturers). 

The Measurz monitoring portal can convey an abundance of system operating information, although the display options to select the desired information are not always intuitive. As with all other battery storage systems that we tested, additional time is required to educate both installers and customers on the critical system operating parameters, as well as on how the Measurz portal operates. 

Operation and maintenance

Operation of the Phazr battery system is completely automatic once the system is installed and configured. The system has built-in protections against operating in extreme temperature conditions. Contractors have visibility into the performance of individual solar panels, building electricity demand from the utility, total building electricity usage and battery operating parameters.

Once communications are established, JLM Energy support has access to virtually all software-configurable settings of the battery. As utility electric rates change, JLM has the capability to update system operating parameters to maximize savings. JLM provides a standard 10-year battery warranty; an extended warranty for an additional 10 years is available.

Summing up

JLM’s Phazr is a unique battery storage system that solves several problems typical with ordinary systems: It is very modular, the battery is easy to install underneath each solar panel, and no additional wall space is required. Moreover, JLM has done an excellent job of documenting its components and explaining the installation procedure. 

On the flip side, there are no backup power capabilities, and not all the components are from the same supplier, so there is more complexity from a networking and configuration standpoint. As with all other systems that include building energy consumption monitoring, installing the necessary current transducers and communications is not an easy task.

For the small 3.3-kWh system tested, the total Phazr battery system cost was $1,726/kWh. Note that this cost includes installation, but does not include inverters. Compared to a larger 10-kWh battery-only system, this cost per kWh is relatively high. Nevertheless, the initial cost of $5,715 is a low entry-level price for a completely installed battery storage system.

Perhaps the biggest drawback of the Phazr battery approach is that the efficiency and longevity of rooftop batteries is not yet proven. Nevertheless, we fully expect that — as with microinverters and optimizers — batteries can and will be engineered to operate reliably under hot, cold and wet rooftop conditions.

Overall, JLM has done a good job integrating the various components. The Phazr battery is a relatively easy and inexpensive add-on to rooftop solar systems using microinverters. For homeowners interested in energy arbitrage and maximizing their self-consumption of solar power (essentially recapturing the lost benefits from net metering changes), the JLM Phazr system is well worth considering. 


The following specifications are for the 0.66 kwh Phazr-8 battery. Depending on model and panel voltages, Phazr batteries range in size from 0.50 to 0.99 kWh.