String Inverters Explained: How to Choose the Right One for Your Solar Project

The inverter is the brain of every solar system. It takes the direct current (DC) electricity your panels produce and converts it into the alternating current (AC) that powers your home, business, or the grid. And while there are several inverter architectures to choose from — microinverters, power optimizers, central inverters — string inverters remain the most widely deployed technology in solar installations worldwide, for very good reason.

At Portlandia Electric Supply, we carry 347 string inverter models from industry-leading brands including Solis, SMA, SolarEdge, Fronius, Chint Power, GoodWe, MidNite Solar, Delta Electronics, and General Electric — covering everything from residential rooftop systems to utility-scale solar farms. Here's a complete guide to understanding string inverters and finding the right one for your project.

What Is a String Inverter?

A string inverter works by connecting multiple solar panels in series — forming a "string" — and converting the combined DC output of that string into grid-compatible AC power in a single, centralized unit. Because one inverter handles all the conversion for a group of panels, string inverters offer a simpler, lower-cost architecture than panel-level electronics like microinverters.

This design makes them the preferred choice for:

• Residential rooftop installations with consistent sun exposure across the array
• Commercial rooftop and ground-mount systems with straightforward roof/land layouts
• Utility-scale solar farms using high-power three-phase models up to 275 kW per unit
• Hybrid solar-plus-storage projects using inverters with integrated battery management

String Inverter vs. Microinverter: Which Is Right for You?

Both technologies convert DC to AC, but they do so at different points in the system. Understanding the trade-offs is key to making the right design decision.

For clean, unshaded arrays — especially at commercial or utility scale — string inverters consistently deliver superior economics without sacrificing performance.

Key Technology: MPPT

Every quality string inverter includes Maximum Power Point Tracking (MPPT) — a real-time algorithm that continuously adjusts the inverter's operating voltage to extract the maximum available power from the string, even as sunlight intensity shifts throughout the day or across seasons.

Higher-end models feature multiple independent MPPT inputs, which allows a single inverter to manage strings oriented in different directions (e.g., east and west-facing roof sections) or at different tilt angles — each optimized independently. Many of our Solis and SMA utility-grade units feature 12–14 MPPT channels per inverter.​

Brand Spotlight: What We Carry

Solis — High-Power Utility Leader

With deep inventory across dozens of Solis models, we're one of the leading Solis distributors in the U.S. Top models include:

• Solis 255kW 3-Phase 14-MPPT (10-Year Warranty) — $14,816.79 | SKU: PES-SPS-SIV-0297
• Solis 255kW 3-Phase 12-MPPT (5-Year Warranty) — $12,653.98 | SKU: PES-SPS-SIV-0293
• Solis 185kW 3-Phase 14-MPPT (10-Year Warranty) — $12,745.66 | SKU: PES-SPS-SIV-0298
• Solis 185kW 3-Phase 12-MPPT (10-Year Warranty) — $12,571.20 | SKU: PES-SPS-SIV-0294

Solis inverters are designed for 1500V DC systems and are field-proven at utility scale across the U.S., delivering high efficiency in demanding environments.​

SMA Solar — German Engineering, Global Standard

SMA's Sunny Highpower PEAK3 series represents the gold standard in high-power string inverters for commercial and utility-scale applications:

• SMA SHP FLEX-US-21 180 kVA 690VAC — $18,500.58 | SKU: PES-SPS-SIV-0734
• SMA SHP 172-US-21 172 kVA 660VAC — $17,031.60 | SKU: PES-SPS-SIV-0735
• SMA SHP 165-US-21 165 kW 1500V — $16,309.44 | SKU: PES-SPS-SIV-0729
• SMA SHP 125-US-21 125 kW 480VAC — $15,932.96 | SKU: PES-SPS-SIV-0736

SMA inverters are fully bankable, UL-listed, and widely accepted by project lenders and tax equity investors — a critical factor in commercial and utility project financing.​

Fronius — 49 Models for Every Scale

Fronius is one of the most trusted inverter brands in residential and light commercial solar. With 49 Fronius models in our catalog, we carry the widest Fronius selection available for U.S. installers.​

Chint Power — High-Output Value

The Chint 275 kW 3-Phase String Inverter (SCH275KTL-DO/US-800) delivers 1500VDC input, 12 MPPT channels, and 800Vac output at $14,649.00 — one of the highest-output-per-dollar utility inverters in our lineup.​

MidNite Solar — Off-Grid & Hybrid Specialists

MidNite Solar's MNXWP series integrates inverter and charge controller functions for robust off-grid and hybrid applications, starting at $10,474.37. These are ideal for remote sites, microgrids, and battery-backed systems where grid independence is a priority.​

SolarEdge, GoodWe & Delta — 70+ Additional Models

We also carry 64 SolarEdge models, 6 GoodWe units, and 2 Delta Electronics inverters — ensuring that regardless of your project spec, brand preference, or budget, we have a match.​

Grid-Tied vs. Hybrid String Inverters

Standard grid-tied string inverters are optimized for one job: converting solar DC to AC and exporting to the grid or powering connected loads in real time. They're the most cost-effective solution for systems without battery storage.

Hybrid string inverters add integrated battery charge and discharge management, allowing the same unit to handle solar conversion, battery storage, and grid interaction in a single device. Key advantages include:

• Fewer system components and less wiring complexity
• Seamless transition between solar, battery, and grid power
• Backup power capability during grid outages
• Optimized self-consumption for commercial peak shaving and demand charge reduction

If you're designing a solar-plus-storage system — or planning to add storage in the future — a hybrid string inverter is a future-proof investment.

How to Size Your String Inverter

Proper inverter sizing is critical to system efficiency and compliance. Key rules of thumb:

1. DC-to-AC ratio — Most residential and commercial systems target a 1.1–1.25 DC-to-AC ratio (i.e., slightly oversize the panels relative to inverter capacity) to maximize inverter utilization
2. Voltage windows — Ensure your string voltage at minimum temperature stays within the inverter's maximum input voltage; at maximum temperature, stays above MPPT minimum voltage
3. MPPT channel matching — Each MPPT input should connect to strings of equal length and identical orientation for best performance
4. Three-phase vs. single-phase — Commercial, industrial, and utility systems almost always require three-phase inverters; residential systems typically use single-phase units

Why Source From Portlandia Electric Supply?

• 347 string inverter models across 10+ brands — the deepest catalog available from a single U.S. supplier
• Tier 1 and bankable brands accepted by project lenders, tax equity investors, and EPCs
• EOL (End-of-Life) upgrade inventory for cost-sensitive projects and replacements
• Container-load and pallet pricing for MW-scale procurement
• Nationwide delivery with logistics support for project sites across the U.S.
• NABCEP Partner | BBB A+ Rated | UL Listed Equipment

Ready to Spec Your Inverter?

Browse our full String Inverter collection — 347 models ready to ship — or connect with our team to get a custom quote for your project.

📞 (888) 876-0007 | 📧 connect@portlandiaelectric.supply

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