My 6-Step Solar Installation Checklist: Don’t Make the Mistakes I Did (Sunrun vs. the Rest)

Why I Wrote This Checklist (and Why You Need It)

When I first started managing solar installations at my company back in 2020, I assumed the most expensive quote was the best. Three blown budgets, two delayed projects, and one near-miss with a battery fire later, I realized I had it completely backward.

I've been in the renewable energy space for about five years now, handling residential and small commercial orders. I've personally made (and documented) around 12 significant mistakes—totaling roughly $8,400 in wasted budget for my clients and my employer. Now I maintain our team's internal checklist to prevent others from repeating my errors.

This checklist is specifically for homeowners or small business owners considering solar, especially if you're confused by the big players like Sunrun, Momentum Solar, or even Tesla. It’s based on real screw-ups, not theory. Follow these six steps, and you'll avoid the worst of what I've seen.

The Checklist That Would Have Saved Me $5,000

Step 1: Don’t Assume the Lowest Quote is Best (Why I’m Not Anti-Momentum Solar)

The numbers said go with Vendor B—15% cheaper with similar specs. My gut said stick with Vendor A. I went with my gut. Later learned Vendor B had reliability issues I hadn't discovered in my research (surprise, surprise). That lesson alone cost me a $2,300 rewire because the installers cut corners.

When comparing Sunrun vs Momentum Solar, don't just look at the initial cost. Look at the contract terms. Sunrun offers a buyout option on their leases, which is a nice flexibility. Some competitors (I won't name them here) lock you in for 25 years with minimal escape clauses. I've seen people try to sell a house with a leased system they couldn't transfer—that’s a nightmare. My advice: ask the sales rep directly, “What’s my buyout price at year 5?” and watch their face.

Checkpoint: Get 3 quotes. Ask each about contract termination, buyout, and transfer costs.
(Note to self: I really should have done this before signing my first lease.)

Step 2: Verify the Actual Equipment (Panel Wattage Matters a Lot)

I once ordered 24 panels based on a sales pitch that said “high efficiency.” Turns out, “high efficiency” meant 360-watt panels when the industry standard for that space was moving to 400-watt. I ended up with a system that produced 25% less than my neighbor's identical-sized array. The most frustrating part: I paid the same price.

When you look at Sunrun solar panel wattage, they typically use panels from Qcells or REC—usually around 390 to 400 watts now (as of early 2025). That’s solid mid-range stuff. But I've seen quotes from other installers slap in 330-watt panels and call it a day. If your roof is small, wattage is king. A 400-watt panel takes up the same space as a 330-watt panel but produces 20% more power.

Checkpoint: Ask for the exact panel model number, look up the manufacturer’s datasheet, and check the efficiency rating (want >20%). Never accept “high efficiency” without the number.

Step 3: Understand Your Battery Options (and That Disconnect Switch)

I only believed in the importance of a battery-disconnect switch after ignoring a warning from my electrical inspector. I had a system installed without a proper external disconnect. The technician had to crawl into a tight attic to cut power during a fault. It was dangerous, slow, and illegal (I learned that the hard way).

If you're getting a battery like Sunrun’s Brightbox, or any other system, ensure there's a clearly marked battery-disconnect switch accessible outside your home. This is code in many jurisdictions (NEC 2020 and later). It’s not optional. And if an installer says you don't need one, walk away.

On the question that everyone asks: how long do solar battery last? It depends. For lithium-ion (like Brightbox or Tesla Powerwall), the lifespan is typically measured in cycles. Expect 5,000–10,000 cycles at 80% depth of discharge. For daily cycling, that’s about 10–15 years. But heat kills batteries. If your battery is in an unconditioned garage in Phoenix, it'll degrade faster. (Based on DOE and manufacturer specs.)

Checkpoint: Ensure your contract specifies a battery-disconnect switch and ask for the battery's “usable capacity” and “life expectancy in years at your location.”

Step 4: Factor in the 'Time Certainty' Premium (It's Not About Speed)

In September 2022, I was coordinating a large project for a client who needed solar operational before a tax credit deadline. We got a quote from a smaller local installer that was $4,000 cheaper than the national player (Sunrun). But Sunrun had a guaranteed install date. The local guy said “probably 6-8 weeks.”

We went cheap. The local guy showed up late, his crew didn't finish on time, and the permit process dragged. My client missed the tax credit by 4 days. That “savings” of $4,000 turned into a loss of over $7,000 in missed credits.

This is the time certainty premium. In a crunch situation (like before a tax credit deadline), the certainty of a firm install date from a bigger player like Sunrun is worth paying for. Missing a deadline because you tried to save a few hundred dollars with a less certain timeline isn't a savings—it's a loss. (We paid $400 extra for rush delivery on a separate project in March 2024. It saved a $15,000 event. Worth every penny.)

Checkpoint: Ask for a guaranteed installation date in writing. If they say “estimated” or “likely,” add 30% buffer to your timeline.

Step 5: Don't Overlook the 'Small Stuff' (Like Panel Chargers for Phones)

This might sound silly, but I've seen people confuse a small USB charger with a real solar system. You can buy a solar panel charger for phone for $30 on Amazon. It's great for camping, but it won't power your fridge during a blackout. That's where a true battery system (like Brightbox) or a generator inlet comes in.

The mistake I made: I assumed a basic inverter would handle sensitive electronics. It didn't. My client's TV had a brownout. Gut vs data: The numbers said the inverter was fine, but my gut said to check the surge rating. I ignored my gut. We had to replace the inverter.

Checkpoint: Yes, get a small solar panel charger for phone as a backup gadget, but don't rely on it for anything else. For your home system, ask about “microinverters vs string inverters” and “surge capacity.”

Step 6: Always Have a Contingency Plan for Installation Delays

The most frustrating part of solar installations: despite the sales pitch, delays happen. The panels don't arrive, the weather turns, the permit office is slow. After the third late delivery in Q1 2024, I created our checklist.

The key: build in a buffer. If a Sunrun (or any) installer says 6 weeks, budget for 8. Ask what happens if they miss their deadline. Do you get a discount? Can you cancel? Most importantly, ensure your contract doesn't penalize you for delays caused by them.

Checkpoint: After signing, ask for a milestone schedule. If you're cutting it close to a deadline (like a tax credit), have a plan B—even if it means paying more for a guaranteed slot.

Final Warning: Read the Fine Print on Your Contract

The errors I've documented cost us a total of about $8,400 over 5 years. The biggest single mistake was signing a contract without reading the “Termination for Convenience” clause. We couldn't get out when the vendor changed the equipment. So glad I now have this checklist—almost missed the battery-disconnect requirement again last month.

Dodged a bullet when I double-checked the quantities before approving. Was one click away from ordering 10x what we needed.