DELTA Pro Ultra: Running 2 or 3 Units with Smart Home Panel 2

A single EcoFlow DELTA Pro Ultra gives you 7,200W of whole-home backup, 6 kWh of base battery, and 5,600W of solar input. For most homes, that is enough. But for larger homes, higher-draw loads — heat pump water heaters, well pumps, electric ranges, EV charging — or owners who want multiple days of autonomy without a generator, one unit is not enough. EcoFlow designed the DELTA Pro Ultra system to scale: up to three units can work together through a single Smart Home Panel 2, delivering up to 21,600W of output and 16,800W of combined solar input.

Adding a second or third unit is not just a battery capacity upgrade — it changes what loads you can support simultaneously and how long you can sustain them. Owners on DIY Solar Power Forum running multi-unit configurations report sustained whole-home coverage averaging 18 kWh per day across heating, kitchen, garage, and refrigeration loads. This guide walks through how the three-tier capacity system works, how the units connect through the SHP2, and what the solar input scaling looks like across a full three-unit array.

The three capacity tiers: 7.2 kW, 14.4 kW, 21.6 kW

Each DELTA Pro Ultra inverter delivers 7,200W of continuous AC output. The combined output of a multi-unit system is additive: two units give 14,400W, three units give 21,600W. This matters for which loads you can run simultaneously during an outage. A single unit’s 7,200W ceiling makes it difficult to run a central air conditioning compressor (typically 3,000–5,000W), a well pump (750–2,000W), kitchen loads, and EV charging simultaneously. Two units at 14,400W combined opens up combinations that would overload a single unit. Three units at 21,600W can sustain virtually any residential load profile, including whole-house air conditioning on a large home.

The per-unit output limit is enforced by each unit’s inverter, not by the SHP2. If your 12 backed-up circuits draw a combined 10,000W during an outage and you have only one DELTA Pro Ultra, the unit will fault at its 7,200W continuous ceiling. The SHP2’s circuit priority settings can shed lower-priority circuits automatically to stay within the limit, but if your critical loads alone exceed 7,200W, a second unit is the only solution. Map your circuit wattages before deciding how many units you need — the monitoring data from the SHP2 provides accurate per-circuit wattage in the EcoFlow app after installation.

How multiple units connect through the Smart Home Panel 2

The SHP2 has three AC input ports — labeled AC1, AC2, and AC3 in the installation guide — each sized for one DELTA Pro Ultra inverter connection. The Infinity Cable (EcoFlow’s proprietary high-current cable) runs from each DELTA Pro Ultra’s output port to the corresponding SHP2 AC port. Your licensed electrician connects the SHP2 to your home’s main panel as a sub-panel, then runs the 12 backed-up circuit breakers from the SHP2 rather than from the main panel. When the grid is present, the SHP2 passes grid power through to those 12 circuits transparently. When the grid goes down, all connected DELTA Pro Ultra units switch those circuits to battery in under 30ms.

The EcoFlow app sees all three connected units as a single unified energy source. It does not require you to configure which unit powers which circuit — the SHP2 distributes load across connected units automatically. During charging, the app coordinates charging from solar and grid across all units based on your configured schedules and priorities. If one unit reaches its maximum charge rate while the others are still accepting charge, the app manages the distribution accordingly. From the user’s perspective in the app, the three-unit system looks like one large battery with one large inverter rather than three separate devices.

Solar input scaling across multiple units

Each DELTA Pro Ultra unit has an independent MPPT solar input that accepts up to 5,600W of DC panels (voltage range 12V–150V, current up to 50A). This is DC-coupled solar — panels connect directly to the unit with MC4 connectors and an XT60 adapter, with no external charge controller or inverter required. A two-unit system accepts 11,200W of solar total across both units’ independent inputs. A three-unit system accepts 16,800W total. Each unit’s MPPT controller operates independently, which means you can have different panel configurations on each unit — different wattages, different string voltages, different orientations — as long as each individual array stays within one unit’s input specs.

The solar-first charge logic in the EcoFlow app can be configured to charge all units from solar preferentially before drawing from the grid, using the per-unit MPPT inputs. With 16,800W of solar input capacity across a three-unit system and reasonable panel coverage (thirty 550W panels would just reach that ceiling), a sunny day can fully charge the entire battery bank without grid power. For installations targeting energy independence or grid independence, this DC-coupled approach — with panels sized to match the total MPPT input of the multi-unit array — is the preferred architecture. Our solar charge time guidecovers the watt, voltage, and string sizing math for a single unit; the multi-unit case simply multiplies the per-unit capacity by the number of units, with each unit’s array sized to stay within its own 5,600W / 50A ceiling.

Battery capacity and expansion across units

Each DELTA Pro Ultra inverter pairs with at least one dedicated battery unit. The base DELTA Pro Ultra battery is approximately 6 kWh of usable capacity. EcoFlow sells additional DELTA Pro Ultra battery units that connect to the same inverter, stacking capacity. A single inverter with two batteries carries roughly 12 kWh; with three batteries, around 18 kWh. Across a three-inverter system with multiple batteries per inverter, total capacity can exceed 40 kWh — well into the range required for multi-day whole-home coverage.

The practical decision for multi-unit owners is how to balance inverters and batteries. Adding a second inverter increases output capacity (7.2 kW → 14.4 kW) and also adds at least one more battery’s worth of base capacity. If your primary constraint is battery runtime rather than simultaneous output, adding batteries to an existing single inverter is more cost-effective than adding a full second inverter. The second inverter only makes sense when your critical loads’ combined peak wattage regularly approaches the single-unit 7,200W ceiling. To estimate your system’s runtime needs precisely, the DELTA Pro Ultra X whole-home capacity guide walks through daily kWh calculations for common load profiles.

Transfer switch options for multi-unit whole-home backup

The SHP2 handles transfer switching automatically for its 12 circuits — under 30ms transfer time is built in, with no manual intervention required. For owners who need more than 12 circuits backed up, or who want to integrate the DELTA Pro Ultra system with the main panel rather than through a sub-panel, a manual transfer switch or an auto-transfer switch (ATS) wired to the main panel is an alternative architecture. In this layout, the electrician installs a transfer switch between the utility and the main panel, and the DELTA Pro Ultra (or multiple units) connects to the load side of the switch. When the grid drops, the ATS opens the utility connection and closes the connection to the DPU system, powering the entire main panel from battery.

This whole-main-panel approach allows backing up all circuits — not just 12 — but loses the per-circuit priority management and monitoring that the SHP2 provides. Owners running large loads who need more than 12 circuits backed up sometimes use a hybrid: the SHP2 for the most critical 12 circuits (medical, refrigeration, communications, HVAC) and a manual transfer switch for the rest of the panel as a secondary option. The SHP2 remains the primary recommendation from EcoFlow and most forum installers because the sub-20ms automatic transfer and per-circuit monitoring are more reliable than manual switch operation during an actual outage.

Adding a second or third unit: sequencing the installation

Starting with a single DELTA Pro Ultra and SHP2 and planning to add units later is a valid approach. The SHP2 is pre-wired for up to three units at installation — your electrician connects AC1 and leaves AC2 and AC3 open. When you are ready to add the second unit, the electrician connects it to AC2 (no SHP2 replacement needed) and the EcoFlow app provisions the new unit into the existing system. The second unit’s solar input, battery, and output are immediately visible in the app alongside the first unit’s.

The main practical consideration for staged installation is conduit sizing: if your electrician runs conduit from the main panel area to the SHP2 location, ask them to size it for the full three-unit cable count even if only one unit is being connected initially. Running conduit for three Infinity Cables initially avoids the need to pull new conduit later when you add units. The cables themselves are not expensive, but the labour to re-run conduit through finished walls is. Similarly, if you are having a concrete pad poured for the battery units, size it for the maximum number of units you eventually plan to install. Adding batteries and inverters to an existing pad is straightforward; adding a second pad later is not. For background on the overall DELTA Pro Ultra whole-home architecture, our guide to whole-home modular storage covers the load-balancing and redundancy principles that inform unit count decisions.