Quick definition
A solar system can't legally connect to the utility grid just because it's installed and ready to go. The utility has to formally review and approve the connection first, through an interconnection agreement: a contract laying out the technical and operational terms both sides agree to, including things like any export limit, required safety equipment, and billing arrangement.
This process typically runs alongside, or right after, the local building permit process, but it's a separate step handled directly with the utility rather than the city or county.
At a glance: most installers handle the interconnection application on the homeowner's behalf as part of a standard installation, though the homeowner is typically the one who signs the final agreement.
Why it matters
Interconnection agreements exist because a grid-tied solar system doesn't just consume power, it can also send power back out onto lines the utility has to manage safely. The utility needs to know a system exists, verify it meets required safety standards like proper anti-islanding protection, and confirm the local grid infrastructure can handle it, before that system is allowed to actually connect and start exporting power. In the US, these technical requirements trace back to IEEE 1547, the national standard for interconnecting distributed energy resources like solar with the grid, which the Energy Policy Act of 2005 established as the basis utilities are expected to build their interconnection processes around.
This is exactly why a system can't just be flipped on the moment installation finishes. Even a fully wired, fully inspected system typically has to wait for formal utility approval, sometimes called permission to operate, before it's legally allowed to connect and begin exporting. Turning a system on before receiving that approval isn't just against process, it's a real safety concern for anyone working on nearby grid infrastructure.
The agreement itself also sets terms that matter well beyond the installation date. Export limits, required equipment, and the applicable billing structure are usually all referenced or defined here, which is why it's worth homeowners actually understanding what they're signing rather than treating it as pure installer paperwork. The Federal Energy Regulatory Commission's explainer on its interconnection rule describes how generators connect to the grid, and why the process has queues and studies.
Where you'll see this
The grid interconnection cost estimator helps budget for application fees and any required equipment upgrades tied to the interconnection process.
For a commercial project, the commercial solar interconnection cost estimator covers the larger-scale version of the same process.
This term comes up in every grid-tied solar installation, in utility application paperwork, and any time a system's operational terms, like export limits or required safety equipment, need to be referenced formally. DSIRE's database of state incentives and policies lists the interconnection rules that apply in each state, since they vary widely.
Related terms
Frequently asked
No. Operating a grid-tied system without utility approval, sometimes called permission to operate, is both against the interconnection process and a real safety issue, since the utility needs to know the system exists before line workers or others interact with the grid near it.
It varies significantly by utility, ranging from a couple weeks for straightforward small residential systems to considerably longer for larger systems or utilities with a backlog of applications to review. Backlogs are a real and recurring issue: some large utilities have reported average residential approval times stretching well past 100 days during periods of high application volume, more than triple what the same utility managed in an earlier quarter, so it's worth asking a local installer what typical wait times look like right now rather than assuming a fixed timeline.
It typically references the applicable rate structure, whether that's net metering or an alternative billing arrangement, but the underlying rate itself is usually governed by separate utility tariffs or state or provincial regulation rather than negotiated individually in the interconnection agreement itself.
Often yes, or at minimum an amendment to the existing one, since adding battery storage can change how the system interacts with the grid, particularly around export behavior and backup operation. It's worth checking with your utility before adding storage to an already-interconnected system.