A Practical Guide to Designing a Home Solar‑plus‑Storage System
A home solar‑plus‑storage system typically consists of PV modules, energy storage batteries, a hybrid inverter, and a monitoring & management system. Its core objectives are to achieve household energy self‑sufficiency, reduce electricity costs, and enhance power supply reliability. This guide uses a real‑world household consumption scenario to walk you through the scientific process of configuring a PV and storage system.
1. Demand Analysis
The first step is a detailed analysis of the household’s energy needs. This involves tallying the power ratings of all appliances, calculating daily consumption and its time‑of‑use distribution, and factoring in local grid conditions to provide a precise basis for system planning.
In this case study, the appliances are as follows:
3 inverter air conditioners (1.3 kW each)
1 washing machine (1.1 kW)
1 refrigerator (0.6 kW)
1 television (0.2 kW)
1 water heater (1.0 kW)
1 range hood (0.2 kW)
Other miscellaneous loads (1.2 kW)
The total connected load is 8.2 kW, of which critical loads (essential for backup during outages) account for approximately 3.6 kW. The household consumes about 35 kWh per day on average, with roughly 15 kWh during the daytime and 20 kWh at night. The project goal is to achieve full energy self‑sufficiency through the new PV + storage system, while providing 5–10 hours of backup power for critical loads during grid outages.
2. System Sizing & Configuration
Based on the above data and the region’s average peak sun hours, a 13 kWp PV array is required, with an estimated daily generation of approximately 40 kWh—sufficient to cover the 35 kWh daily consumption.
To address the 20 kWh nighttime usage, while accounting for daytime consumption fluctuations and backup requirements with a reasonable safety margin, a 30 kWh storage battery is recommended. When fully charged, this capacity can support the 3.6 kW critical loads for approximately 8 hours, meeting the backup duration target.
PV & Storage Inverter
This project adopts a DC‑coupled architecture, integrating the PV inverter and storage converter into a single unit. This approach offers higher integration and reduced system failure rates. During operation, PV power is prioritised for loads, with excess energy stored in the battery or exported to the grid.
We selected a 10 kW hybrid off‑grid inverter, featuring:
Maximum PV input power: 16 kW
AC off‑grid output: 10 kW
IP66 protection rating
Seamless grid‑to‑off‑grid switching capability
This configuration fully accommodates the PV array and load requirements.
Battery Energy Storage System
Common battery types include lead‑acid and lithium‑ion. Considering cycle life, safety, cost, and charge/discharge efficiency, Lithium Iron Phosphate (LFP) chemistry is the preferred choice.
EITAI (Xiamen) New Energy Technology Co., Ltd. offers a comprehensive range of LFP battery solutions tailored for residential applications. For this 30 kWh requirement, we recommend two EITAI ELEMAGIC‑16 LV units connected in parallel.
Key specifications of a single ELEMAGIC‑16 LV unit:
Nominal energy: 16.08 kWh
Usable energy (at 90% DoD): 14.47 kWh
Nominal voltage: 51.2 V, capacity: 314 Ah
Cycle life: ≥ 8,000 cycles (at 90% DoD)
Recommended charge/discharge current: 140 A; maximum: 200 A
Installation: floor‑mounted with 4 universal wheels for easy mobility
Enclosure rating: IP54
Communication ports: CAN, RS485, RS232
Warranty: 5+5 years (5 years free + 5 years technical support)
With two units in parallel, the total nominal energy is 32.16 kWh, and the usable energy (90% DoD) reaches 28.94 kWh. This comfortably covers the 20 kWh nighttime demand while leaving ample margin for temporary load increases or cloudy days. The dual‑unit configuration also enhances system redundancy—if one unit requires maintenance, the other can continue to supply power, improving overall reliability.
Additional advantages of the ELEMAGIC‑16 LV include:
Safer: Cobalt‑free LFP chemistry with an intelligent BMS that provides comprehensive protection against overcharge, over‑discharge, over‑temperature, and short circuits.
Smart: Broad compatibility with major inverter brands via stable BMS hardware; optional Wi‑Fi module enables remote monitoring, adjustment, and firmware upgrades via a mobile APP.
Eco‑friendly: Non‑toxic, pollution‑free modules using recyclable materials.
Convenient: Floor‑standing design with wheels, and supports parallel connection of up to 15 units for easy capacity expansion.
3. System Design
PV Array Design
PV module layout should optimise tilt angle and orientation based on roof structure to maximise solar irradiation. The mounting system must account for roof load‑bearing capacity and safety. Depending on whether the roof is flat or pitched, modules can be flush‑mounted or elevated. The PV array should be connected to the inverter via multiple MPPT strings to enhance generation efficiency.
System Integration
Site Survey & Preparation
Conduct a thorough on‑site survey prior to installation to verify roof conditions and installation feasibility. Develop a detailed construction plan and safety measures to ensure a safe installation process.
Equipment Installation & Commissioning
Strictly follow the construction plan for installing all equipment, including PV modules, mounting structures, inverter, and batteries. Ensure all connections are correct and secure, and perform initial system commissioning.
Regular Inspection & Maintenance
Perform periodic visual inspections of PV modules, inverter, and batteries, checking for physical damage, electrical connection integrity, and operational status to ensure long‑term system stability.
Remote Monitoring & Optimisation
Leverage cloud‑based monitoring platforms to track system performance data and fault alerts in real time. Optimise operational strategies based on actual performance data to continuously improve overall efficiency and reliability.
Summary
In summary, the design process for a residential PV + storage project encompasses a full‑cycle scientific workflow: demand analysis, equipment selection, system design, standardised construction, and intelligent operation & maintenance. Each step must be executed with precision to achieve the dual goals of energy savings, emission reduction, and long‑term economic returns.
With EITAI’s reliable, smart, and high‑cycle‑life LFP battery solutions—in this case, two ELEMAGIC‑16 LV units—homeowners can achieve energy independence with confidence, backed by an industry‑leading 10‑year warranty package and round‑the‑clock technical support.