Research / Methodology
Methodology note
The Fieldline storage project sample
What the sample covers, what “planned” means, and what it leaves out. This note applies to the October 2026 edition of our storage outlook.
What the sample covers
The sample contains 163 utility-scale battery storage projects from 14 US developers, with target operation dates from 2024 to 2026. Together they account for 38 GWh of planned capacity: 8 GWh in 2024, 12 GWh in 2025 and 18 GWh in 2026. Developers contribute between 2 and 31 projects each.
Developers send us project lists, which we check against their public announcements and interconnection filings. Each developer reviews its own entries before an edition is published. We do not publish project-level data or name the developers.
Table 1. Projects in the sample by region
| Region | Projects | Planned capacity (GWh) |
|---|---|---|
| Southwest | 52 | 13.4 |
| Central and Plains | 41 | 9.1 |
| Southeast | 29 | 6.2 |
| Mountain West | 24 | 5.6 |
| Northeast | 17 | 3.7 |
| Total | 163 | 38.0 |
What “planned” means
A project counts as planned when it has a site, a disclosed energy capacity and a stated target operation date. It is counted once, in the target year it carried when it entered the sample, using the earlier of the developer’s first report to us or its first public announcement.
Later schedule changes are recorded but do not move a project to a new year. This keeps each year’s figure stable between editions. It also means a year’s figure is a record of intentions at the time, not of what happened. As of September 30, 2026, developers had moved 3.1 GWh of the 2024 group and 4.4 GWh of the 2025 group to later target dates. Nine projects totaling 1.2 GWh have been withdrawn. Withdrawn projects stay in the year where they were first counted and are flagged in our data.
Planned capacity is therefore a project pipeline. It is not a count of completed installations, and charts based on the sample should not be read as capacity that is operating.
Units
Capacity is energy capacity in GWh at the point of connection, at the start of a project’s life. Grid operators report queue requests in GW of power. A 100 MW project with four hours of storage appears as 100 MW in a queue report and 400 MWh in this sample.
What the sample excludes
- Behind-the-meter systems, including residential and commercial batteries.
- Projects smaller than 20 MWh.
- Projects without site control at the time they would have entered the sample.
- Projects whose storage capacity is not disclosed separately from a co-located solar or wind plant.
- Augmentation of batteries at sites that were already operating.
- Projects outside the United States.
- Operating status. We do not verify whether a project has reached commercial operation.
The constraint survey
Between August 17 and September 25, 2026, we asked each developer to name the single main constraint on each project’s schedule, choosing from connection queue, transformer or other electrical equipment delivery, permitting and land use, battery supply, or other. All 14 developers answered for all 163 projects. The answer is the developer’s judgment, and developers may see their own constraints differently from the grid operators and suppliers they work with.
Limits
The sample is a panel, not a random draw. Larger developers are overrepresented, and so are projects in the Southwest. Figures describe these 163 projects and should not be scaled up to the national market.
Questions about the sample can be sent to the research team through the contact details on our About page.