“Two-day turnaround” means nothing until both sides agree when day one starts. Most disputes with a design vendor are not about speed. They are about a clock that one side thought was running and the other side thought was paused.
Quick answer. A solar design SLA (service level agreement) is the written commitment that defines turnaround for each deliverable type. A useful one sets five things. They are a complete-intake checklist that starts the clock, a business-day turnaround per deliverable, a separate revision window, listed exclusions that pause the clock, and a monthly measurement method. Without the intake definition, the turnaround number cannot be measured.
TL;DR
- The clock should start on complete intake, not on the first email.
- Set turnaround per deliverable type. One number for everything hides the hard jobs.
- Revisions get their own clock, split by who caused the change.
- Write down what pauses the clock: missing data, scope changes, third-party waits.
- Measure on-time delivery monthly from timestamps both sides can see.
This guide is for operations leads at installers and EPCs who buy design work from an outside team. It covers the design clock only.
Permit review time at the AHJ, utility interconnection and PE review run on separate clocks. The PE stamp turnaround guide and the permit approval time data explain them.
What should a solar design SLA cover?
An SLA is a short schedule inside your master service agreement. It should answer six questions in plain terms.
| SLA element | Question it answers | Example wording |
|---|---|---|
| Intake definition | When does the clock start? | ”Clock starts when all items in Intake Checklist A are received.” |
| Turnaround | How long per deliverable? | ”Residential permit set: X business days from clock start.” |
| Revision window | How long to fix comments? | ”Vendor-caused revisions: Y business days.” |
| Exclusions | What pauses the clock? | ”Clock pauses while a data request is open.” |
| Measurement | How is it scored? | ”Monthly on-time rate from ticket timestamps.” |
| Remedy and escalation | What happens on a miss? | ”Two misses in a month trigger a review call.” |
Fill the X and Y values from the vendor’s written offer, not from a marketing page. Then test them on a pilot batch before you commit volume.
When should the turnaround clock start?
Start the clock on complete intake. Starting it on the first email rewards vendors who say yes fast and then wait for data.
A complete-intake checklist for a US residential permit set usually includes:
- Site survey photos, including the main panel label and roof framing.
- Roof measurements or a usable imagery source.
- Module, inverter, racking and storage models.
- Utility name and meter number.
- AHJ name and any local forms.
- Customer name and exact address.
The vendor should confirm intake as complete or list what is missing within a set window. That confirmation is the timestamp that starts the clock.
Fast tip. Put the intake checklist in a web form or ticket template. A form that will not submit without the panel photo removes most clock disputes before they start.
How should turnaround differ by deliverable?
A single turnaround number treats a 7 kW roof and a 2 MW carport as the same job. Set a tier per deliverable instead.
| Deliverable tier | Typical scope | What drives the time |
|---|---|---|
| Sales layout | Panel layout, production estimate | Imagery quality, shading model |
| Residential permit set | Site plan, SLD, structural, labels | Roof complexity, storage, AHJ forms |
| Commercial permit set | Multiple inverters, larger structural scope | Load paths, coordination with other trades |
| Engineering review or seal | Licensed engineer review | Engineer queue, state license coverage |
| Yield report | PVsyst model and report | Weather data source, shading scene |
We have not listed day counts on purpose. No public benchmark covers vendor design turnaround across the US market. Ask each vendor for its written number per tier, then measure it.
How should revisions be handled in the SLA?
Revisions need their own clock. Split them by cause, because the fair answer differs.
- Vendor-caused revision. The set did not match the inputs or the code. These should be fixed fast and at no charge.
- Client-caused change. New equipment, a moved array, a new customer request. These restart some or all of the work and may be billed.
- AHJ or utility comment. The response depends on whether the comment points to an error or to a local preference that was not in the intake.
If the set carries an engineer’s seal, a change usually needs a new review. The guide to revising PE-stamped sets after an equipment swap covers why that review is not optional.
What should pause the clock?
List the exclusions in the SLA. If they are not written down, every pause becomes an argument.
Common exclusions:
- An open data request to the client, such as a missing panel photo.
- A change to equipment, layout or scope after clock start.
- Waiting on a third party, such as a utility map or an engineer of record outside the vendor.
- Public holidays in the vendor’s location, if the SLA uses business days.
Agree how holidays are counted. A vendor in India and a client in the US have different holiday calendars, so name the calendar in the SLA. Our comparison of US domestic vs offshore permit design covers the other trade-offs of a cross-border vendor.
How do you measure a solar design SLA fairly?
Measure from timestamps both sides can see, such as a shared ticket system. Email threads are hard to audit.
A simple monthly scorecard:
| Metric | How to calculate | Why it matters |
|---|---|---|
| On-time rate | Jobs delivered within SLA ÷ jobs due that month | Core reliability measure |
| Intake-to-start time | Hours from first request to complete intake | Shows your own data gaps |
| Vendor-caused revision rate | Vendor-caused revisions ÷ jobs delivered | Quality, not just speed |
| Revision turnaround | Business days per revision | Shows whether fixes are prioritized |
Pair the scorecard with your white label QA checklist defect log. A vendor that is fast but often wrong costs more than one that is slower and right.
Watch out. A turnaround SLA covers the design clock only. No design vendor controls AHJ review time or utility approval, so treat any "guaranteed permit date" with suspicion.
What remedies make sense when the SLA is missed?
Keep remedies proportional and easy to apply. Large penalty clauses tend to slow contract signing without improving delivery.
Options that work in practice:
- Escalation call after repeated misses in one month.
- Priority queue for the next batch.
- Fee credit for a missed job, if both sides agree.
- Exit right after a sustained pattern of misses.
Whatever you choose, tie it to the monthly scorecard, not to a single late job.
How do you test an SLA before signing?
Run a pilot batch of five to ten real jobs across your deliverable tiers. Log the timestamps yourself.
During the pilot, check:
- Did the vendor confirm intake or ask for missing data quickly?
- Did delivery match the written tier?
- How many revisions were vendor-caused?
- Did the sets pass your QA review?
Use the result to set the final numbers. The guide to choosing a solar engineering partner covers the other selection criteria.
How Heaven Designs helps
Heaven Designs provides solar permit design and solar 3D pre-design work for installers and EPCs. We agree turnaround in writing per project or per volume plan, based on scope and complete intake. We do not publish a blanket SLA, because the right number depends on the deliverable mix.
To set up a pilot batch and agree written terms, get a quote. We reply within one business day.
FAQ
What is a typical solar design turnaround time?
There is no reliable public benchmark. It depends on deliverable type, system size, intake quality and the vendor’s queue. Ask for a written number per tier and test it on a pilot batch.
Should an SLA use business days or calendar days?
Business days are common for design work. Name the holiday calendar if the vendor and client are in different countries.
Does the SLA cover AHJ approval time?
No. AHJ and utility review run on their own schedules. An SLA can only cover the work the vendor controls.
Who pays for revisions?
Most agreements make vendor-caused revisions free and treat client-caused changes as new or billable work. Write that split into the SLA.
How often should the SLA be reviewed?
Review the scorecard monthly and the SLA terms when your volume or deliverable mix changes.