Sunnova vs. Building Your Own Solar System: A Cost Controller's Real Numbers

I've managed the energy budget for a mid-sized manufacturing company for six years. Every invoice, every contract, every "unexpected" fee lands in my TCO spreadsheet. When we started shopping for solar in 2024, I did what I always do: compared every approach down to the cent.

This comparison was different. I wasn't just picking panels. I was choosing between two fundamentally different paths: let Sunnova handle the entire solar system (lease, design, install, monitoring, maintenance), or figure out how to build a solar system ourselves from individual components. Turnkey vs. DIY. Managed vs. owner-operated.

I evaluated both across four dimensions: total cost of ownership, reliability and accountability, transferability, and time-to-value. Here's what I found.

Dimension 1: Upfront Price vs. Total Cost of Ownership

This is where most people decide. And I think they decide for the wrong reasons.

Sunnova's solar lease offers a $0-down structure. You pay a fixed monthly rate based on projected production. For a 20 kW system on our roof, the quote came out to roughly $0.12/kWh for production — about $240/month, locked in for 25 years (quote from a Sunnova commercial rep, January 2025). Our utility peak rate is $0.29/kWh. On paper, the lease looked like a no-brainer.

The DIY path looked even better on paper. I priced out a 20 kW system using publicly available solar equipment pricing (January 2025):

• Panels (48 × 420W, tier-1): $6,500
• Inverter (sized per the wattage chart below): $2,800
• Racking and wiring: $3,600
• Permits and inspection: $1,600
• Equipment subtotal: $14,500

Add electrical contractor labor for interconnection ($5,000–7,500 — we collected three quotes), and the upfront cost lands around $19,500–22,000.

That's a real difference. But material cost is only the beginning.

First, inverter sizing. The power inverter wattage chart matters more than most people realize:

• 10 kW DC array → 10–11.5 kW inverter
• 20 kW DC array → 20–23 kW inverter
• 50 kW DC array → 50–57.5 kW inverter

You don't need a 1:1 match. The DC/AC ratio can run 1.15–1.3 without meaningful losses, because panels rarely operate at rated max. We compared string inverters ($1,500–2,200), microinverters ($0.20–0.30/watt), and a central unit ($2,800). We chose a central 20 kW inverter. That was mistake number one.

Mistake number two: maintenance. Solar panels need annual cleaning in our dusty climate ($250–400 per visit). Inverters die. A 20 kW central inverter fails somewhere between year 8 and year 15 — part replacement plus labor runs $3,500–5,000. That's $10,000+ in maintenance over 25 years that the "DIY" conversations rarely mention. NREL's Q3 2024 cost benchmark puts installed commercial PV at roughly $1.50–2.10 per watt — our DIY projection was on the low end, even before maintenance.

Here's the honest math: DIY costs about $32,000–35,000 over 25 years including maintenance. Sunnova's lease costs roughly $72,000 over the same term. The lease is more expensive. Period. I'm not going to pretend otherwise.

The question is what that premium buys you. That's the next three dimensions.

(Note to self: never compare costs without comparing the responsibility that comes with each.)

Dimension 2: Reliability, Warranties, and Accountability

Let me be direct: is Sunnova solar legit? I had to answer this before signing anything.

I checked the basics. Sunnova is publicly traded (NYSE: NOVA). They operate in 20+ states and Puerto Rico. They're a licensed solar contractor in every state they work in. None of that guarantees perfection, but it means there's a regulatory and financial trail if something goes wrong.

The more important factor, from my seat: the warranty. Sunnova's 25-year warranty covers the system components, and — this is the part that matters — labor and replacement costs are included. If an inverter fails in year 8, Sunnova eats the replacement and the labor. No invoice lands on my desk.

With a DIY system, the warranty picture is fragmented:

• Panels: 25-year performance warranty from the manufacturer
• Inverter: 10–15 years (extended to 20–25 for 15–20% more on the purchase price)
• Battery: 10-year warranty, typically
• Labor: $0 warranty — you pay every time someone touches the system

I called four electrical contractors in our area for preventive maintenance pricing. Average quote: $350–600 per visit. That adds up fast. And one $4,000 inverter replacement in year 9 eats 2.5 years' worth of the lease-vs-DIY difference.

The conventional wisdom is that DIY is always cheaper. In my experience, that's only true if nothing goes wrong. The moment you need a repair — and you will need repairs — the gap narrows.

Dimension 3: Transferability & Exit Flexibility

This is the dimension most comparison articles skip, and it changed my recommendation to our leadership team.

Sunnova's solar transfer process is well-documented. The lease can transfer to a new property owner. If your business sells the building mid-lease, the buyer can assume the remaining term — subject to a straightforward credit check (a 10-minute application, based on the process docs I reviewed). The warranty and maintenance continue uninterrupted. That's a genuine advantage.

There's a catch, though. The new owner must accept the remaining lease terms. The Sunnova solar transfer agreement I reviewed includes a $250 transfer fee and a 15-business-day processing window. Not ideal, but workable.

With a DIY system, there's no transfer form. The system is your asset. It stays with the property, and a solar appraisal ideally adds to the sale price. But appraisals are inconsistent. Our commercial real estate broker told me (January 2025) that solar systems add value "about 60% of the time" in our market. The other 40%? Buyers treat it as a maintenance liability.

Then there's the Galileo solar system — Sunnova's integrated solar + battery + EV charging platform. The Galileo system uses an LFP (lithium iron phosphate) battery rated for roughly 6,000–8,000 cycles, versus 3,000–5,000 for NMC chemistries. That means the battery is designed to outlast the lease term. As a procurement person, technology that outlives the contract is exactly the right kind of problem to have.

With a DIY system, you're responsible for every component choice. An LFP battery from a reputable manufacturer costs more upfront ($12,000–18,000 for a 20 kWh system, installed) but lasts longer. A cheaper NMC battery saves money now — and gets replaced sooner. Value over price. Again.

Dimension 4: Time, Effort, and the Cost of Being Your Own Project Manager

Here's what actually happened when we explored the DIY route.

I spent 14 hours researching components. Comparing panel specs, inverter efficiency curves, battery chemistries, racking systems. Another 8 hours collecting and negotiating contractor quotes. Then the county permitting process: 4 weeks. Then the utility interconnection application: 3 more weeks. Total time from decision to grid connection if we went DIY: roughly 3.5 months, if nothing went wrong.

Sunnova quoted 6 weeks from signed lease to interconnection, including permits.

Time is a cost. Our facility pays about $3,500/month in utility bills. Shaving 2 months off the timeline saves roughly $7,000 in avoided utility spend. That doesn't close the $40,000 gap between the lease and the DIY route. But it's real money.

Part of me wants to tell you DIY is the smarter financial move. Another part knows that every hour I spend managing a solar project is an hour I'm not negotiating our other vendor contracts. Opportunity cost isn't zero. It never is.

So Which One Wins?

Depends on your situation. Here's the version I actually gave our leadership team.

Choose Sunnova (or a similar turnkey provider) if:

• You don't have in-house electrical or construction expertise
• You need financing — a $20,000+ capital outlay isn't available
• You want a single point of accountability for 25 years
• You might sell the property within 10 years

Build your own solar system if:

• You have licensed electrical staff or reliable contractor relationships
• You can absorb a $20,000+ upfront expense
• You're comfortable juggling warranties across 3–4 manufacturers
• Your time horizon is 20+ years with no planned move

For us, the tiebreaker was the Galileo system's integrated design and Sunnova's single-vendor warranty. I have mixed feelings about the 25-year commitment. On one hand, it's a long time to be locked into monthly payments. On the other, our utility rates have climbed an average of 4.8% per year for the last decade. A fixed rate at $0.12/kWh starts looking cheap in year 10.

One last note: if you go the Sunnova route, read the production guarantee fine print. No reputable provider promises to "lower your bills by X%" — that's a warning sign. What Sunnova offers is a guaranteed minimum production level. That's the right metric. Specific. Measurable. Tied to actual system performance.

Whether you lease or build, run the TCO analysis before you commit. The cheapest number isn't always the cheapest cost.