A battery storage project looks simple on paper: batteries store energy, inverters convert it from direct current to alternating current, a transformer steps it up to grid voltage. On the ground, it is the most complicated part of the project — and the part most likely to control the schedule.
Here is what is actually happening inside a battery storage project, what choices developers face when picking the architecture, and why the substation usually drives the calendar.
Standalone vs. paired with solar
The most common setup for standalone battery storage is straightforward. The batteries feed inverters that convert their direct current into alternating current. The inverters output medium-voltage AC. That gets stepped up by a transformer to whatever the grid voltage is at the connection point. The grid sees one steady AC source, sized to whatever megawatt rating the project committed to.
When batteries are paired with solar — like a battery storage facility next to a solar farm — there is a second option. The batteries and the solar panels both produce direct current, so they can share a single set of inverters that convert the combined DC to AC. This setup is more efficient because it avoids one round of DC-to-AC-to-DC conversion, but it is more complex to design and operate.
For standalone battery projects, the simpler setup is the default. For paired projects, the choice depends on what the developer is trying to maximize — efficiency favors the shared setup, while operational flexibility favors the standard one. Most large battery projects in 2026 still use the standard setup, even when paired with solar.
How power flows inside the project
Inside a battery storage site, the battery containers are arranged in rows, each feeding a pad-mount transformer. Each container-transformer pair is a single power-conversion unit. The output is typically 600 volts or 1000 volts AC, which is then stepped up to the project’s internal voltage.
For large-scale battery projects, the internal voltage is almost always 34,500 volts. Some older projects used 12,470 volts, but 34.5 kV has become standard because it allows larger blocks of equipment per cable and reduces the total amount of cable needed.
Above 34.5 kV, the substation steps the voltage up again to match the utility’s transmission voltage at the connection point. Typical grid connection voltages are 69 kV, 138 kV, or 230 kV. The choice is set by the host utility — the developer does not get to choose.
Why the substation drives the schedule
The most common question on a battery storage schedule is: when can we energize? The most common answer is: when the substation is ready, not when the battery pad is ready. Battery installation, inverter setup, and cable pulling are roughly 6-month activities at scale. The substation is typically a 9 to 14 month activity from foundation to energize.
On most battery projects, the schedule limit is one of three things on the substation side: how long it takes to get the transformer (50–70 weeks as of 2026), how long it takes to finalize the connection agreement with the utility (3–9 months), or how long the final testing takes (3–8 weeks at the very end of construction).
Our approach is to handle the substation along with the battery pad — same crews, same engineers, same schedule. When both are under one contract, the typical 9–14 month substation build can land in 7–10 months because the civil and electrical work happens in parallel against the same project plan.
Tax credits and the schedule
Federal tax credit qualification adds another schedule dimension that battery developers feel hard. Most tax credit structures depend on the project being completed and put in service by a specific date, with rules that protect projects that started construction by an earlier date.
In practice, these deadlines drive when developers order equipment. They lock in equipment orders before a calendar deadline, then have 12 to 24 months to complete construction. The documentation needed for the tax credit — cost breakdowns, percentage-complete records, in-service dates — gets built during construction and delivered when the project goes live.
We typically handle this documentation as part of construction. The discipline needed is a project management capability, not an accounting one — we build the percentage-complete records the developer needs to qualify for the credit.
Mid-life upgrades
Battery storage projects do not stop at the day they go live. Lithium-ion batteries lose roughly 2 percent of their capacity each year, depending on how hard they are used and how hot they get. To maintain the original rated capacity over a 20-year project life, most projects plan for one or two upgrade cycles — typically at year 7–10 and year 14–17.
These upgrades replace battery cells or racks with newer-generation equipment to restore the system to its original capacity. The work happens during planned outage windows. From a construction standpoint, an upgrade looks like a smaller, faster version of the original build.
Most battery contractors hand the upgrade work off to the original battery manufacturer. We prefer to keep it ourselves — the same crews who built the project know the cables, know the controls, and can sequence the upgrade around the operator’s schedule rather than the manufacturer’s.