BESS & the Duck Curve: Leveraging DERs to Manage Peaks

The duck curve, the duck-shaped chart showing the difference between electric-demand and the amount of available photovoltaic solar available throughout the day, is no longer simply a regional curiosity. It’s showing up more often, in more places, and with a steeper evening ramp than utilities budgeted for. Behind-the-meter distributed energy resources (DERs) including battery energy storage systems (BESS) in particular, are emerging as one of the most affordable ways to flatten that curve, meet rapidly rising demand, and defer the costly infrastructure upgrades utilities would otherwise need to keep the lights on during critical peaks.

 

In This Article

• What is the duck curve, and why is it getting worse?
• From duck curve to critical peak
• Why BTM BESS is an affordable lever
• Grid resiliency and deferred infrastructure costs
• What utilities should weigh before scaling BESS
• FAQ
• Glossary of terms
• Conclusion

 

What is the Duck Curve?

The duck curve gets its name from its silhouette: a high “head” in the early morning, a deep “belly” at midday, and a steep “neck” in the evening. It plots net load, or the total electricity demand minus generation from variable renewables like solar, over the course of a day. This shape emerges because solar output floods the grid at midday, pushing net demand down, only for demand to spike again in the evening as the sun sets and households ramp up appliance use just as solar generation disappears.

This isn’t a theoretical pattern. ISO New England reported that the region logged 134 duck curve days in 2025, up from 107 in 2024, a trend that has climbed steadily since the region’s first duck curve was recorded in 2018. What was once mostly a spring-weekend phenomenon, driven by high solar output and lower weekday demand, now shows up in any season, on any day of the week, as more homes and businesses install rooftop solar.

Frédéric Godemel, writing for Forbes, frames the same dynamic globally: regions from Australia to Germany to Texas are seeing midday oversupply followed by evening shortages, which wastes renewable generation, drives up costs, and strains grid stability. As he puts it, longer and hotter summers are set to expand the belly of the duck and elongate its neck, since extended daylight boosts solar output while rising temperatures push up evening cooling demand at the same time.

 

From Duck Curve to Critical Peak

A duck curve on its own is manageable. The problem is what happens at the top of the neck: the short window each evening when net demand ramps up fastest, often coinciding with the system’s highest cost hours of the year. These are critical peaks, the handful of hours annually that determine how much generation capacity and transmission infrastructure a utility has to build and maintain, even though that capacity sits underused the rest of the time.

Godemel’s Forbes piece notes that battery storage is a straightforward answer to a complex problem: charge on cheap, abundant midday solar, then discharge during the evening peak. But he’s also candid that battery deployment today lacks what’s needed to solve the duck curve on its own, and that a broader toolkit of demand flexibility solutions including virtual power plants (VPPs), demand response, smart EV charging schedules, and better forecasting, has to work alongside storage as electrification accelerates. Ultimately, energy storage, demand-side management, and diversified generation sources all have a role to play in smoothing the curve rather than any single fix.

 

Why BTM BESS is an Affordable Lever

This is where behind-the-meter (BTM) battery energy storage systems earn their keep. Unlike utility-scale, front-of-meter (FTM) batteries, BTM systems sit on the customer’s side of the meter, in places like residential, business, and commercial and industrial properties, and are already proliferating as solar adoption grows. BESS stores excess energy generated during low-demand hours and discharges it when it’s needed most, giving utilities a way to access flexible capacity without waiting years for new generation or transmission to be permitted and built.

The scale of this opportunity is growing quickly. According to the U.S. Energy Information Administration, utility-scale battery storage capacity grew at an average annual rate of 70% over the past three years, reaching 43.6 gigawatts (GW) by the end of 2025 and nearly 52 GW by mid-2026, with another 54 GW planned over the next two and a half years. Much of that growth is paired with solar, allowing operators to store power when wholesale prices are low and discharge when prices and demand spike.

BTM batteries add a second, complementary layer to this trend. Because they’re distributed across thousands of individual sites, they can be aggregated through a Grid-Edge distributed energy resource management system (DERMS) into a virtual power plant (VPP), giving utilities visibility and dispatch control over capacity they didn’t have to build themselves. This decentralization reduces reliance on long-distance transmission, provides backup power during outages, and lets utilities shift aggregated load during peak windows instead of dispatching expensive, carbon-intensive peaker plants.

 

Grid Resiliency & Deferred Infrastructure Costs

The financial case for leaning on BTM BESS during critical peaks is straightforward: it’s often cheaper than the alternative. Utility-scale grid upgrades like new substations, transmission corridors, and peaking capacity are expensive and slow to permit. Aggregating existing, customer-owned battery capacity through demand flexibility programs sidesteps much of that capital expense and timeline. BTM BESS provides considerable ROI for utilities by providing an opportunity for utilities to extend their capital investment into low-to-moderate income communities by subsidizing battery or solar installations in exchange for program participation, which lowers credit risk while adding flexible capacity exactly where it’s needed.

Comparing the two approaches, a breakdown of FTM vs. BTM batteries reveals that front-of-meter batteries offer predictable, utility-controlled output suited to frequency regulation and wholesale arbitrage, while BTM batteries offer distributed load flexibility that flattens evening peaks precisely where demand spikes hardest. Utilities don’t have to choose one over the other; a comprehensive DER strategy that manages both captures the strengths of each.

 

What Utilities Should Weigh Before Scaling BESS

None of this means BESS deployment is risk-free. As the market matures, project success increasingly hinges on more than equipment price and performance: it depends on the commercial structure around that equipment, including supply agreements, warranties, and how contracts hold up under changing regulatory and supply-chain conditions. Furthermore, foreign entity of concern (FEOC) requirements, tariffs, and shifting tax-credit guidance are introducing new risks that need underwriting before contracts are signed, not after. This same due diligence applies to utility-run BTM incentive programs, as utilities must understand vendor durability and how long-term support up front protects the value of the program.

 

FAQs

What causes the duck curve? The duck curve is caused by the growing adoption of solar power. Midday solar generation pushes net grid demand down sharply, then demand rises again in the evening as the sun sets and household and business usage increases, creating the curve’s distinctive “head, belly, neck” shape.

How is the duck curve different from a critical peak? The duck curve describes the full daily net-load pattern. A critical peak is the narrow, highest-cost window within that pattern, typically the steep evening ramp, that drives the majority of a utility’s capacity and infrastructure costs.

Can behind-the-meter batteries really replace new power plants? Not entirely, and not alone. BTM BESS, aggregated through demand flexibility programs, can offset or delay the need for new peaking capacity and infrastructure upgrades, but most experts agree it works best alongside demand response, smart EV charging, and improved forecasting.

Is BESS adoption actually growing, or is this mostly potential? It’s growing quickly and measurably. U.S. utility-scale battery storage capacity grew at a 70% average annual rate over the last three years, and tens of gigawatts of additional capacity are already planned for the next several years.

Do BTM batteries help during outages, not just peak events? Yes. Because they sit on the customer side of the meter, BTM batteries can provide backup power locally during outages while also being aggregated for grid-wide demand flexibility during normal operations.

 

Glossary of Terms

Behind-the-meter (BTM): Energy resources located on the customer’s side of the utility meter, such as home batteries, rooftop solar, or smart thermostats.

Front-of-meter (FTM): Utility-owned or utility-scale energy assets, such as grid-connected solar farms or battery installations, that sit on the utility’s side of the meter.

Battery energy storage system (BESS): A technology that stores electricity, typically from solar or the grid, for use at a later time, helping balance supply and demand.

Distributed energy resource (DER): Small-scale energy assets — solar panels, batteries, EVs, smart appliances — located at or near the point of consumption rather than centralized generation.

Distributed energy resource management system (DERMS): Software that aggregates and manages DER assets, whether utility-held (Grid DERMS) or behind-the-meter (Grid-Edge DERMS), for use in demand flexibility programs.

Duck curve: A graph of net electricity demand over a day, named for its duck-like silhouette, reflecting the drop in net load during high solar production hours and the sharp rise in the evening.

Critical peak: The relatively brief period of highest electricity demand on the grid, which drives the majority of capacity and infrastructure investment needs.

Virtual power plant (VPP): An aggregation of distributed energy resources, coordinated to act collectively like a single power plant for grid services.

 

BESS & the Duck Curve: Conclusion

The duck curve isn’t going away any time soon. If anything, longer solar-heavy days and hotter summers are likely to deepen it further. But the same forces reshaping the curve are also putting more tools in utilities’ hands to manage it. Behind-the-meter battery energy storage, aggregated thoughtfully and paired with demand response and smart charging strategies, offers a comparatively affordable way to flatten critical peaks, extend the life of existing infrastructure, and keep both operational and customer costs in check as demand keeps climbing.