BESS Interconnection
C&I Energy Storage · Kriya Partners
Battery storage projects are sitting in interconnection queues for 5 or more years in some markets. Most developers treat it as a fixed cost of doing business. It isn't always.
The short version
The interconnection queue is the biggest schedule risk in a BESS project
The interconnection queue has gotten bad. New projects applying today in many ISOs are looking at 5-8 year waits for a Generator Interconnection Agreement - the formal contract that says you're allowed to connect at this size, at this point on the grid. No GIA, no project.
Most of the projects stuck in that queue didn't get there because of bad luck. They got there because of application quality - incomplete data, wrong assumptions about bidirectional flow, and restudy loops that sent the application back to the end of the line.
And for some projects, there's a faster path that most developers never check: an existing generator nearby that has interconnection capacity it isn't fully using.
Why BESS interconnection is different
A battery flows both ways - and the study has to cover both
A solar interconnection study checks one direction: can this system push X megawatts onto the grid without breaking anything? A battery study has to check two.
When the battery charges, it's acting as a load - pulling power in from the grid. When it discharges, it's acting as a generator - pushing power out. The utility has to model both worst-case scenarios before it can approve the connection.
Worst-case import (charging)
Battery draws maximum power at the same time as peak local demand. The utility checks: does the combined draw overload local transformers or wiring rated for a lower total? Undersized equipment at the site can trigger required upgrades that change project economics entirely.
Worst-case export (discharging)
Battery discharges at full capacity while local demand is low. The utility checks: does reverse flow cause voltage to rise too high, or confuse protection relays designed to assume power only flows toward loads - not away from them?
Protection coordination is the most common bidirectional-specific problem: fuses and breakers sized for one-way overcurrent may not trip correctly in reverse. This isn't a surprise if the application addresses it. It becomes a restudy trigger when the utility finds it first.
When a battery is paired with solar at the same interconnection point, the application also has to model the scenario where both are operating simultaneously at maximum - the battery charging at full rate while solar is exporting at full output. Net vs. gross capacity needs to be clearly labeled throughout, or the utility will ask - and that question usually comes back as a request to resubmit.
The shortcut most developers miss
Some existing generators have interconnection capacity sitting idle
Every generator that ever connected to the grid has an interconnection right - a GIA that defines how much power can flow through that connection point. Most operating generators don't use their full capacity all the time.
Surplus Interconnection Service (SIS) lets a new battery project attach to an existing generator's underused connection without applying for a new one. The utility has already studied and approved that connection point's total capacity. You're not asking for something new - you're asking to use what's already there.
This is real and growing. SPP has roughly 74 SIS requests totaling about 10,000 MW under review. MISO has about 72 totaling nearly 9,000 MW. Nearly all of it is battery storage. Most developers chasing those projects had no idea the path existed before someone found it for them.
There is a real caveat: SIS rights are subordinate to the host generator. If the host plant retires or loses its interconnection rights, the battery loses them too. It's a faster path, but not a fully independent one. That tradeoff needs to be weighed honestly against the alternative - a 5-8 year queue for a new connection.
When SIS isn't available
Most queue delays are avoidable - not systemic
Even without an SIS opportunity, the cleaner pitch is still true: most projects that get sent back for a restudy get sent back because of the application, not the project. A clean BESS application - one that addresses bidirectional flow upfront, uses verified equipment data, and matches the specific ISO's formatting requirements - doesn't get kicked back to the end of the line.
A clean application covers all of this before it goes in:
- Both flow directions modeled Worst-case import and worst-case export scenarios, not just one direction.
- Protection coordination addressed for both directions Fuses, breakers, and relays verified for reverse flow - not just standard one-way assumptions.
- Charge and discharge rates verified separately Battery capacity isn't always the same in both directions. Asymmetric rates need to be reflected in the study, not defaulted to equal.
- Net vs. gross clearly labeled when solar is co-located The combined worst-case scenario - battery charging while solar exports at maximum - modeled explicitly, not left for the utility to find.
- ISO-specific formatting followed PJM, ERCOT, and CAISO applications have different requirements. What cleared one market's review doesn't automatically clear another's.
These aren't technical surprises. They're known. The difference between a first-pass approval and a restudy that costs 6-8 months is usually whether the application addressed them before the utility found them.
Interconnection isn't just paperwork. It's the single biggest schedule risk in a BESS project - and the one with the most leverage in terms of what good preparation can actually change.
Kriya handles BESS interconnection applications across all major US markets. We build applications around the bidirectional questions utilities will ask before they ask them - and where surplus interconnection opportunities exist near a project site, we find them.
