A new report from the Lawrence Berkeley National Laboratory takes a closer look at customer tradeoffs when it comes to the use of home solar plus energy storage systems, quantifying how utility bill savings and the reliability value from mitigated power interruptions vary with reserve levels.
Home battery storage paired with solar photovoltaic systems can reduce utility bills under certain rate structures while also providing backup power during power interruptions, the lab notes.
“For power interruptions that come with some warning (such as those caused by hurricanes and other natural disasters), customers are often able to charge up their battery in advance. But many power interruptions come without warning,” it said.
To guard against this type of outage, most battery storage systems come equipped with a “reserve setting” that allows the customer to maintain some minimum level of storage capacity in reserve.
“Yet, this feature comes with a tradeoff: the more storage capacity that is held in reserve, the greater the customer’s ability to ride through unpredictable power interruptions, but less capacity is then available to manage utility bills on a day-to-day basis,” the lab said.
The new Berkeley Lab report, Bill Savings vs. Backup Power: Evaluating operational tradeoffs for home solar+storage systems, shows how customers can approach this tradeoff given their particular conditions.
The study quantifies how utility bill savings and the reliability value from mitigated power interruptions vary with reserve levels.
The analysis leverages Berkeley Lab’s PRESTO model, which stochastically simulates power interruption events based on historical patterns in each U.S. county.
The study focuses on ten representative counties and considers a range of common utility rate structures, as well as other key factors, including electricity prices, local reliability levels, and the customer’s value of lost load.
“The study is not a cost-effectiveness evaluation, but rather examines the narrow question of how the value of battery storage to the host customer is impacted by the reserve settings,” the lab pointed out.
Key findings from the report include:
- Reliability value “is (surprisingly) insensitive to reserve level under most conditions.”
- Bill savings drop precipitously with higher reserves.
- Total customer value tends to be greatest when reserves are set as low as allowed.
- Higher reserve levels may increase total customer value for customers with an exceptionally high value of lost load, living in areas with exceptionally frequent power interruptions.
The study builds on earlier work published by the Berkeley Lab team (here and here), evaluating the capabilities of solar plus storage in providing backup power over long multi-day interruptions.
Key findings from the report are highlighted below and will be discussed in an upcoming webinar on October 23rd at 11:00 am Pacific. Please register for the webinar here: https://lbnl.zoom.us/webinar/register/WN_xFm0GAPuRHSnoeoGq40tiQ
