How long does a solar interconnection plan set take?
An outsourced interconnection plan set usually takes one to six weeks and costs $1,500 to $15,000. With Solesca, the pre-CAD design platform for C&I and community solar, you can generate one from the design you already have in about a minute and send it for a PE stamp.
How long does an interconnection plan set take?
Outsourced to an engineering firm, an interconnection plan set for a C&I or community solar project usually takes one to six weeks. Done in house in CAD, plan on four to eight hours of an engineer's time per project.
The range is wide because the work queues up. Your project waits behind the firm's other clients, and each revision starts another round. The utility queue keeps moving while you wait.
What does an interconnection plan set cost?
Developers and EPCs we talk to report paying $1,500 to $15,000 for an outsourced interconnection set. Where you land depends on system size and how much detail the firm puts in.
In house, the cost is engineer hours. Those hours come out of the same people who should be doing detailed design on the projects that already cleared the queue.
What's in a C&I interconnection plan set?
At minimum, a site plan drawn to scale and a single line diagram. Most teams also include the equipment list and inverter settings so the utility can check them in one pass.
| Sheet | What it shows | Who uses it |
|---|---|---|
| Site plan | Array, equipment pads, point of interconnection, poles and parcel line, all to scale | The utility, to see where and how you connect |
| Single line diagram | The path from modules to inverters to boards to transformer to the grid, with ratings | The utility, to study the impact on its system |
| Equipment and settings | Inverter models, gear sizes, protective settings and project notes | The utility, to check equipment against its requirements |
| Bill of materials | String count, inverters, wire sizes and lengths | Your procurement and estimating team |
What information does the utility need from you?
Get the existing equipment right. The utility takes your word for what's on site, so the transformer kVA, the switchgear amp rating and the switchgear voltage need to be correct.
All three are printed on the equipment placards, so take the photo on your site visit. Then ask your construction lead for the interconnection voltage and whether the utility wants a specific transformer winding configuration. Ask procurement which gear sizes you like to buy. Smaller details, like the exact service voltage, usually get corrected in the utility's review.
How do you get a plan set without waiting on an engineer?
Generate it from your design. In Solesca, engineering mode takes your layout, asks how you're interconnecting, and builds the site plan and single line diagram in about a minute.
It checks your choices against the NEC as you go. Pick switchgear too small for your boards and it stops and tells you why. Wire sizes update as you drag a run, and voltage drop updates with them.
You get the set as a PDF ready for a PE stamp, and as a layered DXF if your team wants to bring the sheets into its own title block. Solesca's licensed PE partners cover all 50 states plus DC. Plan sets are an add-on to the Engineering License with unlimited sets, so a revision is just a rerun.
Plan sets cover the PV system today. If your project includes storage, add it in the DXF before you submit. You can see how it works on the plan sets page.
Common questions
Can a generated plan set be stamped?
Yes, for systems up to three transformers, typically around 15 MW. The PDF is ready for PE review and stamp, and Solesca's licensed PE partners cover all 50 states plus DC. Larger systems still export, marked for reference only.
Can I use my own title block?
Yes. Export the layered DXF and bring the site plan and single line diagram into your own template.
Does it include battery storage?
Not today. Plan sets cover the PV system. Add storage in the DXF before you submit.
Is an interconnection set the same as a 30% set?
No. An interconnection set is what the utility needs to study your project. A 30% set adds civil, structural and more detailed electrical design, and comes later.