Sungrow Inverter Comparison: String vs Central for Commercial Solar Projects

For the past four years, I've been the office administrator for a 40-person solar EPC company. I manage all equipment ordering—roughly $8M annually across 12 vendors—and I report to both operations and finance. When I took over purchasing in 2021, I figured my job was to squeeze the best price per watt out of every supplier. Turned out the bigger cost difference wasn't between suppliers at all. It was between inverter platforms.

I'm talking about Sungrow string inverters vs Sungrow central inverters. Specifically, the SG110CX string platform and the SG350HX central platform. I've purchased both, installed both, and replaced both. Here's how they actually compare for commercial and small utility-scale projects, across four dimensions: efficiency, installation, maintenance, and total cost.

Why these two?

If you're evaluating inverters at this scale, Sungrow will be on your list. Sungrow's inverter shipments in 2023 exceeded 130GW (Source: Sungrow annual report, 2023)—more than 130GW AC across their lineup. That scale matters for warranty support, firmware updates, and parts availability. But the real question isn't whether Sungrow is reliable. It's which topology makes sense for your specific site.

String vs central is an old debate, and the industry has swung hard toward string for commercial projects. That shift happened for good reasons, but not for every reason. Let me walk through what I've seen, including a few expensive lessons.

Efficiency and MPPT granularity

The SG110CX wins here for most real-world sites. It has multiple MPPT trackers (I want to say 12 on the current version, but verify the exact count for your market). Multiple trackers mean you can put panels on different roof orientations, shade profiles, and tilt angles without dragging down the entire system. On a rooftop with HVAC units, vents, and parapet shadows, this beats any datasheet number.

Central inverters like the SG350HX are designed for open-field, uniform arrays. If you've got wide, clean space with no shadows, there's no real yield penalty—the DC-side combiner structure handles aggregation. But the moment you have east-west facing modules or morning shadows, you're leaving energy on the table that a string system would capture.

I'm not going to tell you string inverters are universally more efficient. Both platforms claim peak efficiency in the 98-99% range. What matters is energy yield on your specific site. That's a crucial distinction most buyers miss.

Installation and site impact

Here's something the string-favoring crowd rarely mentions: central inverters are easier to install at scale. The SG350HX sits on one concrete pad next to an MV transformer. You pour one foundation, pull one set of cables, commission one unit.

String inverters are the opposite. You're mounting dozens of boxes on racking, running AC cabling from each one, commissioning each individually. For a 10MW project, I'd estimate string adds 2-3 extra days of installation labor. That's real money, and it's real schedule risk if the weather turns.

But string installations don't need a crane. I've had sites where the delivery crane for a central unit couldn't physically get in—mud season, tight gates, low utility lines. On a congested commercial rooftop, a central inverter may be impossible to install at all. Two people can carry an SG110CX up a ladder.

Maintenance and outage risk

String inverters have better outage characteristics. Central inverters have better serviceability. Both statements are true, and they point in opposite directions.

If a string inverter fails, you lose one string—maybe 2-3% of the plant. If it's ground-mounted, you can swap the whole unit in about an hour. But if it's on a rooftop, a swap is a multi-hour job involving lifting plans and sometimes roof access paperwork.

I learned this in 2023 when a lightning surge fried two SG110CX units at a school rooftop project. The replacements took our crew a full day and a half, and part of that delay was because we had only one spare in the warehouse. Now I stock at least 5% spares for any portfolio of string-inverter sites.

A central inverter that fails takes down a lot of generation at once. That's the downside. But the replacement is one clean swap with a crane and a certified tech—one day, one unit, done. For a very large site where you can't afford a scaled-down outage over several weeks, central is arguably the lower-risk option. Counterintuitive, but that's what the risk math says.

Total cost of ownership

Price per watt is one line item in a much bigger puzzle. Fully installed cost includes DC combiners, cabling, mounting, labor, network infrastructure, commissioning, and 20 years of projected O&M.

For projects below 5MW, string inverters are almost always cheaper on a fully-included basis. You skip DC combiner boxes, simplify the string design, and reduce engineering time. The SG110CX has become extremely price-competitive, especially since 2023.

For projects above 10MW, central inverters start to pull ahead. One MV transformer, one station, one maintenance point. The cost of stringing together 100+ enclosures, each with its own AC breaker and network connection, adds up faster than spreadsheet models tend to show. In Q2 2024, I ran a fully-loaded comparison for a 12MW ground-mount site and found the central topology came in roughly 15% cheaper on installed cost per watt (based on our vendor quotes and internal labor estimates; verify current pricing).

The crossover point for our projects has been around 7-10MW. Below that, string wins on installed cost. Above that, central wins. It's not about which technology is newer or which one the marketing materials favor. It's arithmetic.

Field notes: testing and small parts

Two small things that have saved us real problems:

Test your DC power supply with a multimeter before commissioning. This sounds basic, but it catches issues that datasheets can't predict. Set your multimeter to VDC, verify open-circuit voltage on each string, and check polarity before connecting to the inverter. We've caught reversed wiring and faulty connectors this way twice in four years. If you're new to this, a quick search for 'how to test power supply with multimeter' will walk you through the safe procedure.

Don't forget the low-voltage battery side on hybrid systems. One of our commissioning schedules slipped by two days because the wrong battery charger arrived on site. The spec required a 4S battery charger for a 14.8V lithium bank (4 cells in series—that's what the '4S' means), and someone ordered a standard 12V unit. On legacy lead-acid sites, we've also kept a 6 volt battery charger in the maintenance kit for cell equalization. These are small line items, but a five-second verification at purchase time has saved us from last-minute logistics more than once.

What should you choose?

I'll be honest about the limits of this advice.

Choose the string topology (SG110CX or similar) if:

• Your site is on a rooftop or has partial shading and multiple orientations
• Your project is under 5MW
• You need phased deployment—bringing arrays online one section at a time
• A crane can't reasonably access your site

For a corporate headquarters with a 1.2MW rooftop array, string is the answer. Period.

Choose the central topology (SG350HX or similar) if:

• You've got an open-field ground mount over 10MW
• The site has solid crane access and room for a concrete pad
• Your O&M team can handle MV equipment

For sites in the 5-10MW range, do the full installed-cost comparison yourself. Don't accept a rule of thumb.

And a final honest note: I order Sungrow regularly, but I won't tell you it's the only serious option. What I can say is that their shipment scale translates to a service network that's been good when we needed it. That said, we had a support ticket in late 2024 that took ten days to resolve (ugh). No vendor is perfect. But in my experience the platform decision—string vs central—has a much bigger impact on your project's lifetime economics than the brand painted on the enclosure.