String inverters, microinverters, DC optimizers, and distributed MPPT — four fundamentally different ways to convert sunlight into usable power. Here's how they work and where each fits.
Panels wired in series form a high-voltage DC string (300–600 V). One central inverter converts DC to AC. The inverter has 1–3 MPPT trackers, each shared across an entire string of 8–15 panels. This is the oldest and most common architecture, accounting for roughly 50% of residential installations worldwide.
Conversion path: Panel DC → Series string (high-voltage DC) → Central inverter → 230 V AC
Each panel gets its own small inverter mounted directly on its back. DC-to-AC conversion happens at the panel level. The AC outputs from all microinverters are wired in parallel to the home's AC bus. Enphase is the dominant manufacturer, with their IQ8 series being the most widely deployed microinverter globally.
Conversion path: Panel DC → Microinverter (per-panel DC-to-AC) → 230 V AC bus
A hybrid approach pioneered by SolarEdge. Each panel gets a DC optimizer — a small DC-DC converter that performs per-panel MPPT and conditions the output to a fixed voltage. The optimized DC outputs are wired in series and fed to a central string inverter. The optimizer handles panel-level tracking; the inverter handles DC-to-AC conversion.
Conversion path: Panel DC → DC optimizer (per-panel MPPT, fixed output) → Series string → Central inverter → 230 V AC
Each panel connects to its own MPPT charge controller. The controllers independently track each panel's maximum power point and output to a common low-voltage DC bus (typically 48 V) that charges a battery bank. A separate inverter converts battery DC to AC. This architecture is native to off-grid and hybrid systems.
Conversion path: Panel DC → Per-panel MPPT controller → Common DC bus → Battery → Inverter → 230 V AC
| Factor | String Inverter | Microinverter | DC Optimizer | Distributed MPPT |
|---|---|---|---|---|
| MPPT tracking | Per string (8–15 panels) | Per panel | Per panel | Per panel |
| Shade handling | Poor — weakest panel limits string | Excellent | Good to excellent | Excellent |
| DC voltage on roof | 300–600 V DC | None (AC on roof) | 300–600 V DC (1 V per optimizer in safe mode) | 30–55 V per panel (low voltage) |
| Battery storage | Requires separate battery inverter (AC-coupled) | Requires separate battery system (AC-coupled) | SolarEdge offers integrated battery inverter | Native — battery is built into the architecture |
| Off-grid capable | No (needs grid reference for anti-islanding) | Limited (Enphase IQ8 can form microgrid) | No (central inverter needs grid) | Yes — designed for off-grid |
| Panel mixing | No — all panels in string must match | Yes | Yes (within optimizer voltage range) | Yes — any panel, any wattage |
| Scalability | Limited by inverter capacity | Add one panel + microinverter at a time | Limited by inverter capacity | Add one panel + controller at a time |
| Single point of failure | Yes — central inverter | No | Yes — central inverter | No (inverter failure stops AC, but DC charging continues) |
| Monitoring | System-level only | Per-panel (Enphase Enlighten) | Per-panel (SolarEdge portal) | Per-panel |
| Typical cost (₹/Wp) | ₹4–6 | ₹8–12 | ₹7–10 | ₹5–8 |
| Typical warranty | 5–12 years | 25 years (Enphase) | 12–25 years (optimizer + inverter) | Varies by manufacturer |
Every conversion step loses energy. The number and type of conversions in each architecture directly affect how much of the panel's output reaches your appliances.
One conversion (DC-to-AC) at 96–98% efficiency. But the real loss is in MPPT mismatch — the string tracker can leave 5–25% of available energy on the table depending on shading and panel variation. Net system efficiency under real conditions: 75–92%.
One conversion per panel (DC-to-AC) at 96–97% efficiency (Enphase IQ8: 97.0% peak, 96.5% CEC weighted). Panel-level MPPT eliminates mismatch losses. However, the conversion happens at panel-level voltages (30–55 V DC to 230 V AC), which is less efficient than converting from the higher voltage of a series string. Net system efficiency under real conditions: 89–95%.
Two conversions: optimizer (DC-DC at 98.8% peak for SolarEdge P505) plus central inverter (DC-AC at 97.5% peak for SE5000H). Combined peak: ~96.3%. Panel-level MPPT reduces mismatch losses. Net system efficiency under real conditions: 88–94%.
Two conversions if used with battery: charge controller (DC-DC at 96–99%) plus inverter (DC-AC at 93–97%). But this architecture inherently includes battery storage, so the comparison isn't apples-to-apples with grid-tied systems. For off-grid and hybrid systems where a battery is needed regardless, the distributed MPPT path is the most direct route from panel to battery — no unnecessary conversions through AC and back.
The battery-native advantage: String inverters and microinverters are designed for grid-tied systems. Adding batteries means AC-coupling: solar DC → inverter → AC → battery inverter → DC → battery → inverter → AC. That's four conversion steps with compounding losses. Alloy Charge's distributed MPPT charges the battery directly from the panel — DC → MPPT → DC → battery — with only one conversion. The battery is not an afterthought; it's the centre of the architecture.
String systems place 300–600 V DC on the roof. DC arcs don't self-extinguish the way AC arcs do (AC crosses zero 100 times per second, giving the arc a chance to extinguish). A 600 V DC arc from a damaged cable or connector can sustain a flame hot enough to ignite roofing materials. This is a documented fire risk — the U.S. National Electrical Code requires rapid shutdown (to under 80 V within 30 seconds) for systems above 80 V DC on the roof.
SolarEdge optimizers address this with SafeDC: when the inverter shuts down, each optimizer reduces its output to 1 V. Enphase microinverters produce AC on the roof, which is inherently safer. Distributed MPPT systems with individual controllers operate at panel voltage (30–55 V per panel) on short runs directly to the controller — inherently low voltage with no series string multiplication.
| Use Case | Best Architecture | Why |
|---|---|---|
| Large commercial rooftop, no shade, grid-tied | String inverter | Lowest cost, minimal mismatch on uniform arrays |
| Residential rooftop, partial shade, grid-tied | Microinverter or DC optimizer | Panel-level MPPT recovers shading losses |
| Off-grid farmhouse or remote property | Distributed MPPT | Battery-native, no grid dependency, modular scaling |
| Hybrid system with battery backup | Distributed MPPT | Direct DC-to-battery path, avoids AC-coupling losses |
| Phased installation (add panels over years) | Microinverter or Distributed MPPT | No string sizing constraints, mix any panels |
| RV, campervan, or boat | Distributed MPPT | 12/24/48 V DC native, compact, battery-centric |
| Resort with multiple buildings | Distributed MPPT | Independent per-building systems, no single point of failure |
Our engineers will evaluate your site, loads, shading, and grid situation — then recommend the architecture that maximises your return.
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