Batteries have many potential applications in the power sector, including back up power, peak shaving, demand charge management, and other uses. Their ability to store energy from sustainable resources, like wind and solar power, could also play a key role in supporting PSE’s clean energy initiatives. Plus, like our customers, PSE is interested in exploring the technology and understanding the best uses for our homes, businesses, and communities.

We’re using lithium-ion batteries for all of our current demonstrations. The size and scale of each project’s battery system is selected on a case-by-case basis, depending on the setting, customer profile (e.g., residential, commercial, or community), and what we’re planning to test. We considered lithium-ion batteries exclusively because of their broad industry appeal, safety record, and history of use in other utility projects across the United States. All of our battery systems are also fully certified to current industry standards.

With our residential and commercial batteries, our first year of testing will help inform our next steps. As for our community demonstrations, we'll know more once we're further along in our planning processes.

In addition to testing each demonstration's respective use case, our overarching goal is to determine the best ways to integrate batteries into our local grid and potentially offer them as a product or service for our customers’ homes, businesses, and communities.

For each of our demonstration projects, we considered several different vendors. In addition to seeking partners who would expand our knowledge base and expertise, our selection criteria included: strong reputations within the industry, previous demonstrated experience with utility pilots and projects, and a commitment to safe and reliable technology. All future vendors and project partners will also be considered on a case-by-case basis and with the same due diligence – and, as always, with our customers in mind.

Similar to how tech companies roll out “beta” versions of new products, using PSE locations for some of our demonstrations will help expedite our learning process and ability to potentially leverage the technology for customers in the future.

All of the batteries for this demonstration have been installed, and PSE is not seeking additional participants at this time.

It depends on the load you anticipate placing on the battery. As an example: the 6kW/15.5kWh residential batteries we’re testing are paired with a “critical load panel” (CLP) that the battery supplies. During an outage, the CLP will only power what the customer has prioritized (e.g., lights, refrigeration, water pumps, and WiFi). Depending on your anticipated energy usage, you may need to consider installing more than one battery or pair it with solar panels.

The amount of back-up power a residential battery can provide depends on its capacity, how much it’s charged, and the load it’s powering. For instance, the Sunverge One batteries we’re testing have a capacity of 15.5 kWh and should potentially provide back-up power, for a critical load, for up to 24 hours. For many of our customers, a critical load would include a refrigerator, a few lights, and the ability to power WiFi or charge a cell phone. Just remember – the larger the load, the shorter the battery life!

Basically, the higher the initial state of charge (%), and the lower the load placed upon the battery, the longer a battery’s charge should last. Battery capacity is typically given in kWh, which is a way of determining how much power the battery can sustain over time, given a certain load. For example, a 15kWh battery can supply 1kW of power for 15 hours (if it’s fully charged).

It depends on the type of battery and the number of charge/discharge cycles placed upon it over time. Currently, most lithium-ion energy storage systems typically last for approximately 5,000 cycles, or between 10 and 15 years.

Some battery systems have the ability to supply power instantly, while others must drop power for a few seconds before re-establishing service. As an example, the residential batteries we’re testing will instantly supply power to the critical load panel (CLP), as long as the battery is adequately charged.

When it comes to consumer-scale battery storage, choosing the right manufacturer and installer will go a long way in mitigating future maintenance. That said, battery storage systems purchased from reputable manufacturers, and skillfully installed, should generally require only routine maintenance (e.g., keeping the battery free of debris/hazards and cleaning the air filters to ensure adequate ventilation).

While batteries are good at storing energy, they can’t generate it. Batteries also pose unique challenges: they can run out of power; their performance can be affected by very hot or cold temperatures; and batteries big enough to service a home, or anything larger, can still be expensive to purchase and install. That’s why we’re testing batteries in a variety of scenarios to determine the most reliable, efficient, and cost-effective applications for our customers.

The prices for battery storage can vary greatly, depending on the capacity of the system and its intended use. If you’re interested in purchasing your own battery storage system, keep in mind that the installation can cost almost as much as the battery itself. Plus, depending on the size of your property, you might need more than one battery to provide adequate back-up power. While the price is expected to continue to drop, you could easily spend several thousand dollars on a small, residential system.

PSE offers installation guidelines for customers who’ve purchased their own battery storage systems. For a number of reasons, it is not recommended that customers attempt to install batteries themselves.

Residential batteries offer a lot of promise and our demonstration projects have provided a lot of data on how to best integrate them into our daily lives and the local distribution grid. We’re continuing to evaluate our battery demonstrations and projects in order to scale to solutions that can meet the targets that we’ve shared as part of our first Clean Energy Implementation Plan. Batteries and other distributed energy resources (“DER”) are key to our goals for decarbonization and we encourage our customers to learn more about the DER customer programs that we’re hoping to make available soon.