Who This Checklist Is For

I've been handling solar and electrical upgrade purchases for homeowners and small commercial properties since 2018. In that time I've made (and documented) 9 significant mistakes totaling roughly $6,400 in wasted budget. Now I keep a pre-signing checklist for our team so nobody else eats those costs.

This list works if you're in any of these situations: comparing a full-service installer against a DIY solar kit, weighing Sunrun vs ADT Solar quotes (or any two companies, honestly), sizing a battery for EV charging, or trying to figure out whether that "free" savings calculator is telling you the truth.

Seven steps. The last one is the one most people skip.

Step 1: Find Out What the Solar Kit Savings Calculator Actually Excludes

That online savings calculator? It's doing math on panel cost alone in most cases. When I bought my first solar kit in 2019, the calculator said I'd save $14,000 over 20 years. What it didn't factor in: permit fees ($680), utility interconnection charges ($450), and a structural inspection that came back saying my roof needed two rafters sistered before anyone could mount anything ($1,100).

Never trust a savings number until you've asked one question: "What's not included in this figure?"

Here's what a legitimate calculator should let you adjust:

  • Your actual monthly kWh usage (pull it from a recent utility bill, not an average)
  • Local sun hours (NREL's PVWatts calculator uses address-level data)
  • Whether you're financing or paying cash (the monthly payment isn't the same as cost)
  • Battery storage or not (it changes the economics in ways most calculators ignore)

I still kick myself for not checking the permit box. If I'd asked, I'd have caught the $680 before signing anything.

Step 2: Read Reviews for Your ZIP Code, Not the Company's Star Rating

"Sunrun solar Orlando reviews" — I've pulled up that exact search. Every major installer has a 4.5+ average somewhere. But the average is national. The install experience is local.

Here's what I do now: I search for the company name plus my county, then read the three-star reviews specifically. Five-star reviews tell you the sales process went well. Three-star reviews tell you what went wrong during installation. One-star reviews are usually about contract disputes and aren't representative.

The most useful thing a three-star review gives you: the specific name of a subcontractor, a scheduling window that went long, or a permit department issue. That's the detail that predicts your experience.

The surprise wasn't how many bad reviews existed. It was that the same problem — "install crew showed up without the right inverter model" — showed up across four different companies. That's an industry pattern, not a brand problem.

Step 3: When Comparing Sunrun vs ADT Solar (or Any Two Quotes), Ask Identical Questions

I've filled out quote comparison sheets for both Sunrun and ADT Solar for clients. The numbers land in different places because the companies bundle differently — one might roll the battery into the lease, the other might quote it separately. That's not deception. It's just architecture. But if you're comparing line items that don't match, you're comparing nothing.

Here's my standard 6-question sheet. Ask every company the same six things:

  1. What's the total cost of the system before any tax credit, and what's the price per watt?
  2. Which inverter brand and model is included, and is it a string or microinverter setup?
  3. What does the lease buyout look like in year 5 and year 10? (Get the formula in writing.)
  4. Who handles permits and interconnection — you or me?
  5. What's the production guarantee, and what happens if the system underperforms?
  6. If I add a battery later, does the existing inverter support it, or do I need to swap equipment?

If a sales rep can't answer all six without a follow-up call, that's not a deal-breaker on its own, but it tells you what the paperwork process will feel like.

Step 4: Size the Battery for EV Charging and Household Backup Together

This is the mistake that cost me the most in credibility, not cash. In 2022, I sized a client's battery at 10 kWh based on their historical household usage alone. Six months later they bought a used Chevy Bolt. Their evening charge sessions drained the battery by 9pm on backup mode, and they called me furious.

EV charging and home battery storage live on the same circuit in your head. They shouldn't live on the same budget without math.

Quick numbers to anchor this (verify against current specs, since models change):

  • An average U.S. home uses about 10,500 kWh per year — roughly 29 kWh per day (EIA, 2023 data)
  • A typical EV adds 3,500-4,500 kWh per year, or 10-12 kWh per day if you charge at home most nights (U.S. DOE, Alternative Fuels Data Center)
  • A single Brightbox-class home battery is usually in the 10-13 kWh usable range — enough to shift evening usage, not enough to also carry an EV and a heat pump through an outage

Bottom line: if you're planning an EV in the next three years, size the battery for that scenario now. Retrofitting a second battery later costs more than the upgrade does today — and the inverter may not support it.

Step 5: Check Inverter Specs — Whether It's on Your Roof or in a Semi Truck

People ask me about how to install a power inverter in a semi truck. Different world from rooftop solar, but the same math applies: continuous vs peak wattage, wire gauge, and fusing. In 2021 I helped a driver spec a 2,000W inverter for a sleeper cab and we ran 10 AWG wire. The wire got hot enough to soften insulation during a long idle. We should've been on 4 AWG. That was a $310 redo plus an afternoon on the ground.

The principle translates directly to solar. A solar inverter is rated for continuous output over 25 years. If the installer quotes a string inverter rated at 95% of the panel array's peak output, the inverter clips production on the sunniest hours of the year. No one tells you that in the sales pitch. It's not a scam — it's a design tradeoff — but you should know which tradeoff you're buying.

Ask this question: "What's the DC-to-AC ratio on this design, and why did you pick it?" If the answer is "1.2" and the rep can explain it, you're dealing with someone who knows the tradeoff. If the answer is "what's a DC-to-AC ratio," you've learned something useful about the quote.

Step 6: Read the Quote for What's Not Written on It

Here's my transparency soapbox, and I'll keep it short: the quote that looks higher but lists every fee is almost always cheaper than the quote that looks lower and adds things later.

In 2020 I signed a $3.99/watt quote that ballooned to $4.79/watt by the time installation finished. Where did the 80 cents go? A "trenching surcharge" not mentioned in the proposal, a "panel upgrade" the utility forced because the main breaker couldn't handle the new load, and a "monitoring package" that turned out to be mandatory, not optional.

I've learned to ask "what's NOT included" before I ask "what's the price." The vendor who lists all the fees upfront — even if the total looks higher — usually costs less in the end.

Three questions that surface hidden costs:

  • "What's the all-in price after permits, interconnection, and any utility-required main panel upgrade?"
  • "What's the cancellation or change-order fee if I modify the design after signing?"
  • "What's the escalation rate on the lease payment, and what's the cap?"

Any answer that includes the phrase "it depends" is your cue to ask for a range in writing.

Step 7: The 24-Hour Pre-Signature Check

This is the step I skipped in 2020, and it's the one that would've saved me the most money. Before signing anything, take 24 hours and confirm these six things:

  1. Roof condition. Get the installer to put in writing that they inspected the roof and it can support the array. If they won't, that's a red flag, not a formality.
  2. Production estimate methodology. Ask which tool produced the number (Aurora, Helioscope, PVWatts) and what shading assumptions went into it. My 2020 estimate assumed "no shading" — there was a mature oak tree 30 feet from the array. I ate the production shortfall, not the installer.
  3. Inverter warranty vs panel warranty. Panel warranties are often 25 years. Inverter warranties are often 10-12. Find out the replacement cost when the inverter fails — because it will.
  4. Lease vs loan end-of-term. If it's a lease, get the buyout formula in writing. If it's a loan, confirm the APR, not just the monthly payment.
  5. Interconnection timeline. Utility approval can take 4-12 weeks depending on the state. Confirm who owns that delay risk.
  6. Assignee clause. If you sell the house, does the buyer have to qualify for the lease? If yes, you've just narrowed your buyer pool.

I still kick myself for not getting the shading assumption in writing. The production gap cost the client about $1,100 in utility bills over 18 months that the estimate said wouldn't exist.

Common Mistakes and Notes

Three patterns I see repeatedly:

  • Trusting a savings calculator over a utility bill. The calculator uses averages. Your bill uses your life. Use the bill.
  • Comparing leases to loans without normalizing. A $99/month lease over 25 years is $29,700. A $24,000 cash purchase with a 30% tax credit is $16,800. Same system, wildly different economics. Know which structure you're actually comparing.
  • Assuming battery rebates are guaranteed. Federal tax credits apply to storage in many cases (IRS Form 5695), but state and utility rebates vary and expire. Verify at the state energy office and your utility's current program sheet.

Pricing references here are ballpark as of early 2025; verify current rates before quoting anyone. Solar pricing in particular moves with module costs and interest rates, so a quote from last quarter may not be competitive today.

My last piece of advice: the best installers I've worked with say "I don't know" more often than the bad ones. The bad ones have an answer for everything, including the questions they shouldn't be able to answer without a site visit.