A Quality Inspector's 5-Step Solar Lease Checklist: What Most Specs Get Wrong

Who This Checklist Is For

If you're a facility manager or procurement lead evaluating solar lease proposals for a commercial property—and you don't have time to become a solar engineer overnight—this one's for you.

I review commercial solar and battery storage specifications for a living. Roughly 200 proposals a year, covering everything from panel wattage to LFP battery thermal management. And I can tell you: the first draft of a solar lease spec is almost never correct. In Q1 2024 alone, I rejected 38% of first-round proposals for discrepancies that would have cost the client.

Here's a 5-step checklist I use. It's not exhaustive, but it catches the mistakes I see most often.

Step 1: Start With Your Load Profile, Not the Solar Guy's Pitch

Most mistakes start here. A vendor shows you a slick deck with estimated savings, and you start nodding before you've even looked at your own utility bills.

Don't.

Before you talk to anyone, pull 12 months of your facility's electricity usage data. Hourly if you can get it. At minimum, monthly. This is your baseline. Everything else—system size, battery capacity, payback period—gets calculated from this.

I've seen proposals where the system was sized for the facility's average load, not the peak. That's fine for offsetting general consumption, but if you're adding EV chargers or running refrigeration, your peak load is what matters for demand charge reduction. A battery sized for average load won't touch your demand charges.

Checkpoint: Do you have verified utility data for at least one full year? Does the proposal reference specific months or just say "based on typical usage"?

Step 2: Verify the Battery Chemistry—It's Not All the Same

Here's where I see the most expensive assumptions.

Lithium-ion is a broad category. Within it, LFP (lithium iron phosphate) and NMC (nickel manganese cobalt) behave very differently. Sunnova's residential offering uses LFP, which is common for commercial applications too—but not every vendor is transparent about which chemistry they're quoting.

I assumed once that "lithium battery" was specific enough. It wasn't. Turned out the vendor had quoted NMC for a 50,000-unit annual order where our client specifically wanted LFP for thermal stability and cycle life. The re-spec cost us a $22,000 redo and delayed the project by six weeks.

What to look for:

• Cycle life: LFP typically offers 4,000–6,000 cycles vs. 2,000–3,000 for NMC. If the proposal doesn't specify cycle life at a given depth of discharge, ask why.
• Thermal management: A heated LFP battery (common in colder climates) is different from a standard one. If your facility is in a region with freezing temps, this matters.
• Warranty terms: Some manufacturers warranty throughput (total energy cycled), others warranty calendar life. They are not the same thing.

To be fair, NMC has higher energy density, so if space is your constraint, it's worth considering. But know the trade-off.

Step 3: Lock Down the O&M Language Early

This is the step most people skip. They focus on the hardware specs and the monthly lease payment, and they treat operations & maintenance as boilerplate.

Big mistake.

A typical solar lease is 20–25 years. Over that period, you will have inverter failures, panel degradation beyond spec, and—if you have battery storage—BMS (battery management system) issues. The question isn't if, it's who pays and how fast.

Specifics to nail down in the contract:

• Response time for critical vs. non-critical faults. ("Commercially reasonable efforts" is not a commitment.)
• Guaranteed minimum power output over the lease term. This is negotiable.
• Who covers balance-of-system repairs—wiring, combiner boxes, monitoring equipment. I've seen leases where the panel is covered but the wiring to the inverter isn't.
• Performance monitoring access. Can you see real-time data, or only the vendor's monthly report?

To be fair, most vendors will include a standard O&M package. But the details vary. I've rejected proposals simply because the O&M section used phrases like "as needed" instead of specific timeframes.

Step 4: Cross-Check the Installation Timeline—Realistically

I have mixed feelings about rush service premiums. On one hand, they feel like gouging. On the other, I've seen what happens when a project timeline slips: missed utility rebate deadlines, delayed building openings, and in one case, a $15,000 event that couldn't happen without temporary power.

The point isn't whether to pay for speed. The point is to know what the realistic timeline is before you sign.

In March 2024, we paid $400 extra for rush delivery on a transformer. The alternative was missing a $15,000 event. That was an easy call. But the real trick is avoiding the situation entirely by setting realistic expectations upfront.

Ask the vendor for a project timeline with specific milestones: permit application, equipment procurement, installation start, commissioning, interconnection approval. Then add 20% to every estimate. If it fits your deadline, great. If not, you have a conversation about priorities—or budget for expediting.

I'm not 100% sure every vendor pads their timelines, but in my experience, the ones who promise "6 weeks from contract to commissioning" are either lying or cutting corners on permitting.

Step 5: Demand a Commissioning Test Protocol in Writing

This is the step I see missed most often. The system gets installed, the vendor says it's working, and you sign off. Six months later, you find out the battery is only discharging at 60% of rated capacity because of a configuration error.

Been there. It's not fun.

Before you accept the installation, require a written commissioning test protocol that includes:

• Panel output verification (measured vs. modeled, under standard test conditions if possible).
• Battery charge/discharge cycle test at rated power for at least one full cycle.
• Inverter efficiency check.
• Monitoring system verification—can you see real-time data on your end?
• Emergency shutdown test.

If the vendor pushes back on a formal commissioning test, that's a red flag. Every major manufacturer includes commissioning procedures in their installation manuals. It's not extra work—it's standard practice.

Common Mistakes and What to Avoid

A few things I've learned the hard way:

• Don't assume "standard" means the same thing to every vendor. I've seen three different interpretations of "standard commercial solar lease" in the same week. Always get the specifics in writing.
• Watch out for performance guarantees that exclude too much. Some leases guarantee output but exclude "force majeure events" that the vendor defines broadly. Ask for a list of exclusions.
• Don't let the urgency of a deadline push you into skipping verification. A rushed decision that goes wrong costs more—usually way more—than the delay would have caused.
• If the price seems too good, check the interest rate on escalators. A lower monthly payment might just mean a higher annual escalator. Over 20 years, that adds up.

Bottom line: solar leasing can work great for the right facility. But like any long-term contract, the details matter. Use this checklist, and you'll catch most of the gotchas before they cost you.