PV DC Coupling vs AC Coupling — Which Should You Choose?

Why do you have to choose?

A Solar + Battery system works mainly at the DC level (PV generates DC, the battery stores DC), but the grid and load are mostly AC — so you need an inverter / PCS to convert the energy.

There are two ways to design it:

• DC Coupling — connect solar to the battery directly at the DC level
• AC Coupling — solar and battery are separate, each through its own inverter

Both work — but there's a trade-off you have to choose.

---

DC Coupling — coupled at the DC level

Structure

PV feeds the charge controller (e.g. LEONICS SCM/SCB Series) — converting DC voltage from PV → battery — using a single inverter for battery → grid.

Pros

• High efficiency — DC→AC conversion happens once (vs twice in AC Coupling)
• Lower cost — no separate solar inverter needed
• Fast off-grid response — the battery takes PV directly, without AC inversion
• Solar clipping recovery — energy the inverter would clip can be recovered and stored in the battery

Cons

• More complex design — requires voltage matching between PV and battery
• Hard to retrofit — if solar already exists, adding a DC-coupled battery is difficult
• Brand lock — charge controller + inverter should be the same brand

---

AC Coupling — coupled at the AC level

Structure

PV goes through a solar inverter (DC→AC) → AC bus → load — the battery runs through a separate PCS (AC↔DC).

Pros

• Simpler design — solar and battery operate independently
• Easy retrofit — with existing solar, a battery can be added immediately
• Mix brands — solar inverter brand A + battery PCS brand B is fine
• Scalable — add batteries later without affecting solar

Cons

• Lower efficiency — converts DC→AC→DC→AC (2-3% loss)
• Higher cost — needs both a solar inverter and a battery PCS
• Slower off-grid response — latency from two AC inversions

---

Side-by-side comparison (example system)

An example 100 kWp solar + 200 kWh battery system for a factory:

---

How to choose? — Decision Tree

Use DC Coupling if:

• It's a new project designed from scratch (greenfield)
• You want maximum efficiency (solar farm + BESS)
• You need fast off-grid response (UPS, microgrid)
• You want solar clipping recovery
• It's large, >100 kWp (bigger savings)

Use AC Coupling if:

• You already have solar and want to add a battery (retrofit)
• You want to mix brands of solar and battery
• Scalability is the priority (add batteries later)
• It's a small system, <30 kWp (the difference is minor)
• Your team isn't comfortable with DC voltage matching

---

LEONICS models for DC Coupling

LEONICS has two series of solar charge controllers for DC Coupling:

SCM Series (low PV, high battery)

• SCM-345160 — 50 kW, PV 200-900Vdc, Battery 250-950Vdc
• SCM-320 — 100 kW
• SCM-480 — 150 kW

Best for: low-voltage PV array, high-voltage battery

SCB Series (high PV, low battery)

• SCB-500110 — 50 kW, PV 250-950Vdc, Battery 200-900Vdc
• SCB-220 — 100 kW
• SCB-330 — 150 kW

Best for: high-voltage PV array, standard-voltage battery

Both series offer 98% efficiency and a wide voltage range.

---

For AC Coupling — use the MTP-620x

The LEONICS MTP-620x Hybrid Inverter is an all-in-one that supports both DC Coupling (via built-in MPPT) and AC Coupling (via the battery PCS port) — choose as needed in a single unit.

---

Summary

There's no one-size-fits-all answer — it depends on:

• Project size
• Greenfield or retrofit
• Your existing vendors
• Priority: efficiency vs flexibility

Rule of thumb:

• New + large project → DC Coupling
• Existing + want to add a battery → AC Coupling

---

LEONICS uses both couplings in real systems — DC-coupled with the MTP-620x hybrid inverter for C&I microgrids, and AC-coupled with Modular PCS for larger BESS. See how they fit a factory solar + storage solution or a utility-scale BESS project, or size a rooftop system first with Solar Insight Pro.

Want advice on which one your project should use? — the LEONICS team designs both, comparing ROI before installation — contact us or call 02-746-9500