You got three bids. One is noticeably cheaper. Here's what you need to know before you sign anything.

_{TL;DR: A low commercial solar bid often leaves out permitting costs, prevailing wage, warranties, and O&M. Those gaps don't disappear. They turn into change orders, underperforming systems, and costly surprises down the road. This guide shows you what a complete proposal looks like and gives you a checklist to use on your next bid review.}

That Low Bid Might Be Missing More Than You Think

If you're comparing commercial solar proposals and one comes in noticeably lower than the rest, it's worth slowing down before you call it a win. Energy costs keep rising across California, and more businesses are going solar to get ahead of them. But a growing number of contractors are winning bids by leaving things out rather than doing the work more efficiently.

What's Usually Missing From a Low Commercial Solar Bid?

There are a few line items that show up consistently in complete proposals and consistently get left out of the cheaper ones. Here's what to look for.

Are permitting costs included in your solar proposal?

Pulling permits isn't optional. Every legitimate commercial solar installation requires electrical and building permits, and those fees vary by city and county. If a proposal doesn't mention permitting, you'll likely see it pop up as a change order once the project is underway.

A straightforward question gets you a long way here: "Are permit acquisition, submission, and associated fees included in this contract?" A contractor doing things right will say yes without hesitation.

Is the bid prevailing wage compliant?

If your project requires prevailing wage labor rates under California law, a bid that ignores this is almost certainly underpriced. They're not planning to pay those rates. According to the California Department of Industrial Relations, prevailing wage requirements apply to a broad range of commercial and public works projects.

Ask directly, and get the answer in writing. A contractor who's doing it right won't hesitate to confirm.

_{Quick note on prevailing wage: If your project falls under prevailing wage laws, which apply to a lot of commercial and public-sector work in California, a contractor who doesn't mention it in their bid may simply not be complying. That's your liability, not theirs. It's worth asking about upfront.}

You can read more about Prevailing Wage here: How Prevailing Wage is Shaping California’s Solar Industry

Does System Design Affect How Much Energy You Actually Get?

Two proposals with the same number of panels and similar price tags can produce very different amounts of energy over time. The difference usually comes down to design decisions the contractor makes, and they may not bring them up unless you ask.

Flat racking vs. tilted racking: what's the difference?

On a flat commercial roof, panels can be mounted flat or at a slight tilt, typically around 10-15 degrees. Tilted racking produces more energy and sheds water better, so panels stay cleaner longer. Flat racking is cheaper to install and can fit more panels on the same roof, which might make a proposal look more impressive on paper.

But don't let a bigger system fool you. Flat-mounted panels are less efficient, collect more dirt and standing water, and tend to drive up maintenance costs over time. A well-designed tilted system will often outperform a larger flat one and cost you less to maintain over a 25-year system life.

If a proposal only shows one option, ask them to model both. The difference in annual energy output and payback period can be meaningful.

Is your roof ready for a 25-year solar commitment?

This is the design question that gets skipped most often, and it can lead to the most expensive surprise. A solar system lasts 25-30 years. If your roof has 8-10 years of life left, you're eventually looking at a mid-life reroof with a full solar array sitting on top. That means removing and reinstalling the whole system, a cost you definitely don't want.

A thorough contractor will assess your roof before designing the system and provide a clear plan to align the two lifespans. That might mean re-roofing first, doing both at the same time, or at minimum, flagging the issue so you can plan for it. We recently worked with a commercial property owner in the Santa Clarita Valley who had this exact situation. By coordinating the roof replacement and solar install together, they avoided what would've been a costly mid-life removal and saved significantly on both scopes.

Is the full electrical scope included?

Getting solar connected to the grid requires coordination with your utility and sometimes upgrades to your existing electrical infrastructure. This work needs to be fully scoped in any proposal you're evaluating. If it's vague or missing, there's a good chance it shows up as an add-on later.

Who's Actually Doing the Installation Work?

Here's a question a lot of buyers forget to ask: Does this contractor have their own crews, or are they managing subcontractors?

Many solar companies operate more like project managers. They sell the job and hand off the electrical and roofing work to third parties. That creates gaps in accountability, especially around warranties and quality control. Contractors with their own in-house journeymen electricians and roofing crews can answer for their work directly. No finger-pointing, no runaround, just a team that owns the outcome from start to finish.

While you're at it, ask about licenses and certifications. In California, look for:

• C-10 electrical contractor license
• C-39 roofing contractor license
• General contractor license if the scope includes structural work

Ask who's managing the project from start to finish, too. In-house engineering and project management means faster decisions, fewer handoff errors, and someone with real accountability on the line from design through final inspection.

Does the contractor have in-house engineering and project management?

Engineering sign-offs on structural and electrical design are required for any permitted commercial solar project. Contractors with their own engineers can move faster, catch design issues earlier, and keep projects on schedule.

Ask whether the engineer of record is an internal team member or an outside firm. And ask who your dedicated project manager will be, someone accountable from the design phase all the way through final inspection.

What Should a Commercial Solar Warranty Actually Cover?

Warranties are one of the most important parts of any solar proposal, and one of the easiest places to hide vague language. Here's what a solid proposal should include for each major component:

• Panels: 25-year linear performance warranty, plus a 10–12 year product warranty
• Inverters: 10–25 years depending on the type (string inverters vs. microinverters). Confirm what's actually being proposed
• Racking and mounting hardware: A structural warranty covering wind and seismic loads
• Workmanship: The installing contractor should warranty their own labor for at least 2–5 years. If it's not written down, it doesn't exist.

Who's actually backing the workmanship warranty?

Find out whether the contractor is using their own crews or subcontracting the work. If they're subbing out the electrical and roofing, who's actually holding the workmanship warranty? And how long have those subs been in business?

In-house crews mean cleaner accountability. There's no "you'll have to call the sub" when something needs fixing three years down the road.

What happens after installation? Does the proposal cover O&M?

O&M stands for operations and maintenance. It covers the ongoing inspections, cleaning, and monitoring your system needs to keep performing at its best over its lifetime. A lot of proposals don't say a word about what happens after the install crew leaves, which is a bigger deal than it sounds.

A solar system that isn't monitored is a solar system that can quietly underperform for months before anyone notices. Panels get dirty, inverters throw errors, and shading conditions change. Without someone watching the data, you won't know until your energy bill tells you something's wrong.

Ask what the contractor's O&M program looks like, who monitors the system, and how quickly they respond when something's off. Ask whether monitoring is included in the contract or billed separately. If the answer is vague or the topic seems like an afterthought, that's worth noting before you sign.

Commercial Solar Proposal Checklist

Run through this before you make your final decision. If anything is missing or unclear, ask. A solid contractor will have answers.

Commercial Solar Proposal Checklist

Run through this before you make your final decision. If anything is missing or unclear, ask. A solid contractor will have answers.

Costs & Scope

     ☐ Permitting fees included

     ☐ Prevailing wage addressed (if applicable)

     ☐ Utility interconnection scope included

     ☐ Roof condition assessed and addressed

System Design

     ☐ Energy production model matches actual racking design

     ☐ Flat vs. tilted racking explained with rationale

     ☐ Roof lifespan addressed

     ☐ Full electrical scope defined

Contractor Qualifications

     ☐ In-house vs. subcontracted crews confirmed

     ☐ Licenses provided: C-10, C-39,and GC if applicable

     ☐ Engineer of record identified

     ☐ Dedicated project manager named

Warranties

     ☐ 25-year panel performance warranty

     ☐ 10–12 year panel product warranty

     ☐ Inverter warranty type and duration stated

     ☐ Racking/structural warranty stated

     ☐ Workmanship warranty with duration and the responsible party named

O&M

     ☐ Post-installation O&M plan and pricing is outlined

     ☐ System monitoring is included or clearly priced separately

     ☐ Response time for service issues is stated

So What Does a Good Commercial Solar Proposal Actually Look Like?

The cheapest bid isn't always the cheapest project. What looks like savings upfront can turn into change orders, underperforming systems, and costly surprises, especially when you're locked into a 25-year commitment.

Asking the right questions now protects your budget and helps you find a contractor who'll actually stand behind their work long after the install crew leaves. The contractors worth working with will welcome these questions. The ones who dodge them are telling you something.

If you're sorting through proposals and want a second set of eyes, we're happy to help. No pitch, no pressure, just a straight conversation about what you're looking at.

Ready to compare proposals or want a second set of eyes on a bid you've already received? We're happy to help, no pitch, no pressure.

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FREQUENTLY ASKED QUESTIONS

Q: How long does a commercial solar installation typically take from contract to energization?
A: It depends on system size and site complexity, but most commercial projects run 8-16 weeks from signed contract to utility approval. Permitting timelines vary significantly by jurisdiction and are one of the biggest wildcards. A contractor who's done a lot of work in your area will have a realistic sense of local timelines and should be able to give you a project schedule with milestones, not just a vague completion estimate.

Q: What's the difference between a string inverter and a microinverter, and does it matter for my building?
A: A string inverter is a single unit that converts power from an entire row of panels. A microinverter is a small unit attached to each panel. Microinverters tend to perform better when panels face different directions or deal with partial shading, since one underperforming panel doesn't drag down the rest. For large open commercial rooftops with consistent sun exposure, string inverters are often more cost-effective. Your contractor should explain the tradeoff for your specific roof.

Q: What happens to my solar system if I sell the building?
A: A solar system generally transfers with the property and can be a selling point, especially as energy costs rise. If the system was financed with a loan, it typically gets paid off at closing or assumed by the buyer. A Power Purchase Agreement (PPA), where a third party owns the system, and you pay for the power it produces, involves its own transfer process that requires buyer approval. It's worth understanding your financing structure and how it affects a future sale before you sign anything.

Q: Does commercial solar affect my property taxes in California?
A: California has a property tax exclusion for active solar energy systems, meaning the added value of a solar installation generally won't increase your property tax assessment. This exclusion has been extended several times and currently runs through 2026. It's worth confirming the current status with your tax advisor, but historically, it's been a consistent benefit for commercial solar owners in the state.