I'm an office administrator for a 45-person company. I manage facility purchasing—roughly $240,000 a year across 14 vendors, from office supplies to electrical contractors. When someone asks me whether they should install solar, add a battery, or put in an EV charger, they usually expect a brand recommendation. I ask a different question first: what problem are you solving?
There is no universal answer. There's only your load profile, your utility rate, and your risk tolerance. That's why the same company can end up with three different decisions for three different buildings.
There is no universal answer. There's only your load profile, your rate tariff, and your risk tolerance.
The first fork: what are you optimizing for?
Most energy projects fall into three buckets. Cost: the building uses a lot of electricity during the day. Resilience: the site needs to keep working when the grid does not. Electrification: people and fleets need charging. Each bucket has a different logical starting point.
One thing I tell people before they get too deep in the search: don't start with 'solar vs. wind' at the building scale. If you look at the countries with the most wind turbines, China, the U.S., and Germany usually top the list. Utility-scale wind works. But a turbine on a commercial lot brings zoning, structural, and wildlife-related questions that solar does not. That's not a knock on wind; it's a category fit issue. For most distributed sites, solar is the more practical starting point.
Scenario A: high daytime consumption and peak demand
If your property draws real power while the sun is up, solar is the first system to model. This is where Vivint Solar often comes up. Since Sunrun acquired Vivint Solar in 2020, the sales and service operation is part of a larger national company. The product logic is still straightforward: solar offsets grid consumption, and a battery moves that energy into the hours when the sun is down.
You'll see an older phrase on online forums: Vivint Solar LG Chem. The LG Chem RESU was a common battery pairing in those systems. It's a capable battery, but don't assume a current quote still includes it. Ask for the exact model and data sheet in writing. We didn't have a formal approval chain for change orders when I started this role, and it cost us when an unauthorized 'expedited permit' fee landed on the final invoice. Now if the battery chemistry or inverter model isn't written down, it's not part of the deal.
Check the legal entity, too. On many contracts, the signing entity is Vivint Solar Developer LLC—a limited liability company. That's common with large installers, but it matters because warranties and financing registrations are tied to a legal entity. Ask what happens if that entity changes. You want the equipment warranty to follow the product, not the company name.
Financing is another branch. A lease or PPA lowers upfront cost and moves performance risk to the provider, but it gives up tax benefits if your company can use them. Buying opens up depreciation and the investment tax credit, but puts maintenance on you. Neither is always right.
And be skeptical of savings calculators. Per the FTC's Green Guides and business guidance on advertising, claims should be truthful and substantiated. If a vendor says a payback period is guaranteed, request the written assumptions: utility rate, year-over-year escalation, system degradation, and battery round-trip efficiency. Plug those into your own spreadsheet. You don't need software—you need honest inputs.
In our 2024 vendor consolidation project, I sent every bidder the same spreadsheet template so they had to fill in the same assumptions. Some vendors didn't like it. That was a clue. The ones who did made the comparison easy. So glad I checked the performance guarantee wording on the final contract—almost signed the lower bid with no production guarantee. If the system performed 15% below projection, we would have absorbed the loss.
Scenario B: backup power and the truck inverter question
If the problem is resilience, the conversation changes. A battery can carry a critical load for a while, but only if it's sized to the load and the outage duration. Solar may recharge it during an outage, depending on the inverter's islanding capability and system design. Don't let a sales rep say 'solar means you have backup power' without explaining how that actually works.
I was once asked about a 10,000 watt power inverter for truck—mounted in a vehicle for tools and lighting. That's a completely different design. A 10 kW inverter can power tools or a mobile command post, but the truck's electrical system has to supply that input. A standard 12V alternator cannot sustain a 10 kW draw; you're looking at dual alternators, bigger battery banks, or a 24V/48V architecture. Same word—inverter—but none of the same assumptions.
For a fixed site, I ask four questions: What loads must run in an outage? For how long? Can the battery carry that actual starting load? And how many cycles per year do you expect? Battery warranties are usually stated in cycles to a retention percentage, like 5,000 cycles to 60% capacity. That's not a marketing slogan; it's the boundary you'll live with.
Dodged a bullet on that exact issue once. I was one signature away from a battery with a smaller throughput warranty. It would have worked, but early degradation would have made it an expensive failure after year five. (Mental note: always read the throughput section, not just the calendar warranty.)
Batteries also degrade. Anybody who says theirs will never need replacement is overselling. Plan for end-of-life replacement in the budget. If the financing term is longer than the warranty, ask why.
Scenario C: Level 2 EV charging for people, fleets, and the home version
The third scenario is EV charging. This one is interesting because it's both a workplace decision and a home decision. When employees start asking for charging, the facility manager catches it first. Then someone asks, 'how do I set up a Level 2 charger at home?'
The process is similar in both places. You need a 240V circuit, enough panel capacity, and a charging station. The real work is the load calculation. If the panel is full, you don't just add a breaker; you may need a subpanel or a service upgrade. NEC Article 625 covers EV charging equipment, and local inspectors will want a permit. That permit is not a formality—it's the paper trail that protects you.
For a home install, a common setup is a 40-amp continuous charge on a 50-amp breaker. For a commercial lot, you may want load management to run multiple chargers without a new transformer. The cheapest station can become expensive if the location forces you to repave a section of parking lot later. (Which, honestly, is a measure twice, buy once moment.)
People often search for 'how to set up level 2 charger at home' and want a single answer. It's really three steps: confirm panel capacity, choose the charger amperage and cord length, then hire a licensed electrician to pull the permit. If you skip the first step, the project stalls at inspection.
How to tell which scenario you're in
Still unsure? Open your last 12 utility bills and look for three numbers.
- Peak demand. If demand charges are a big slice of the bill, Scenario A is your primary project.
- Outages. If you lost power more than twice in a year, or one outage would cost more than a battery, Scenario B comes first.
- EV adoption. If employees or fleet vehicles already plug in, or your company made an EV commitment, Scenario C is a requirement, not a nice-to-have.
Once you know which scenario drives the decision, you can evaluate vendors on that basis. Whether the quote is from Vivint Solar, a local EPC, or a separate battery supplier, start with the load. Check the legal entity. Verify the warranty in writing. And don't let a single payback number replace your own common sense.