All-in-One vs Modular Home Energy Storage Systems: Which Solution Fits EV Charging Applications? | OLINK Energy Storage Manufacturer

All-in-one home energy storage systems can be installed in 1–2 hours and work well with single 7 kW EV chargers. Modular stackable systems can scale from 10 kWh to over 30 kWh and support 11–22 kW multi-EV charging. For projects with uncertain future growth, modular designs can reduce upgrade costs by up to 40% compared with replacing a fixed all-in-one unit.

Article Overview

Architecture comparison: Understand the core differences between all-in-one and modular energy storage systems from a procurement perspective.

Six-dimensional comparison: Compare installation, scalability, output power, cost, maintenance, and space requirements.

EV charging considerations: Examine power matching, expansion for multiple parking spaces, and peak-valley electricity price arbitrage.

Selection guidance: Use the decision tree and evaluate a third option—the stackable integrated architecture.

Why System Architecture Matters More in EV Charging Applications

When configuring an energy storage system for an EV charging project, choosing between an all-in-one and a modular system is never simply a matter of preference. The decision directly affects the project’s initial investment, installation hours, future expansion costs, and after-sales complexity.

We have worked with many procurement teams and engineering contractors who initially selected an all-in-one system for convenience. However, after adding a second EV, they discovered that neither the power nor the capacity could be expanded. The entire system had to be replaced, resulting in significant losses.

EV charging differs from ordinary residential backup power. It involves continuous discharge under high loads, creating more demanding requirements for output power and usable capacity.

A 7 kW single-phase EV charger represents a continuous 7 kW load. When evening household electricity consumption is added, a small energy storage system with only 5 kW of output will usually be insufficient. Meanwhile, 11 kW and 22 kW three-phase charging places even higher demands on the system’s power rating and parallel connection capability.

Therefore, we recommend answering three questions during the selection stage:

Current charging demand: How many EVs need to be charged now?

Future expansion: Will more charging spaces be added within the next one or two years?

Application type: Is the project a residential single-charger installation or a commercial multi-charger deployment?

Different answers will lead to completely different optimal system architectures.

If you are selecting equipment for a specific project, you can first review our home energy storage system solutions to understand the configuration range of OLINK’s complete residential energy storage portfolio before continuing with the detailed comparison below.

All-in-One vs Modular: The Fundamental Differences Between the Two Architectures

Before discussing system selection, it is important to understand the fundamental logic behind these two architectures.

Many customers ask whether all-in-one and modular systems are simply different ways of stacking batteries. In practice, their structural differences directly affect installation efficiency, expansion flexibility, and after-sales costs.

Structural Characteristics of All-in-One Energy Storage Systems

An all-in-one energy storage system integrates the battery modules, hybrid inverter, battery management system, energy management system, circuit breakers, and communication modules into a single cabinet.

Pre-wiring and system testing are completed before delivery. At the project site, installers only need to connect the PV, AC output, and communication cables before commissioning the system.

Advantages: Fast installation, lower compatibility risks, unified warranty coverage, and a clean appearance.

Limitations: Fixed capacity and power, limited expansion potential, and whole-unit servicing may be required when an internal component fails.

For commercial buyers, the core value of an all-in-one system is standardized delivery. The same product, installation process, and after-sales procedure can be applied across multiple projects.

This provides excellent consistency during large-scale deployment and reduces the technical requirements placed on installation teams.

Structural Characteristics of Modular and Stackable Energy Storage Systems

A modular energy storage system separates the inverter, battery packs, BMS, and distribution box into independent units. Each module can be selected, expanded, or replaced independently.

A stackable system is an advanced form of modular architecture. Its standardized battery modules are installed directly on top of one another while sharing one inverter control and management system.

Advantages: Capacity can be increased as required, power can be upgraded, individual modules can be repaired without affecting the entire system, and investment can be divided into phases.

Limitations: For traditional modular systems, it is more components, more complicated wiring, longer commissioning times, and potential communication compatibility issues between different brands.

For experienced installers and system integrators, modular systems provide greater flexibility and lower long-term costs. However, this requires professional system selection and installation capabilities.

The Fundamental Difference from a commercial Procurement Perspective

Procurement customers frequently ask us which architecture is less expensive. This question cannot be answered with a single statement.

The equipment price of an all-in-one system may be higher, but its installation time is only one-third to one-half that of a traditional modular system. This can reduce the overall project delivery cost.

Modular equipment may offer a lower equipment price, but on-site wiring and commissioning require more labor hours, increasing installation costs.

All-in-one means convenience first: It is suitable for standardized projects, fast delivery, and projects supported by installation teams with average technical capabilities.

Modular means flexibility first: It is suitable for customized projects, applications requiring future expansion, and projects supported by experienced technical teams.

The real decision factors: Customer profile, project scale, and expected growth over the next three years.

A Comprehensive Six-Dimensional Comparison

Concepts alone do not provide an intuitive comparison. The following section compares all-in-one and modular systems across six dimensions: installation, scalability, output power, cost, EV compatibility, and after-sales service.

You can use this comparison directly when presenting solutions to customers.

Installation Complexity and Labor Hours

Installation speed is the most obvious advantage of an all-in-one system.

Two electricians can usually install and commission a standard residential all-in-one system within half a day to one day. A traditional modular system requires the separate installation of the inverter, battery cabinet, and distribution box.

Installers must then complete the DC wiring, communication configuration, and system commissioning. The entire process normally requires one to two days.

All-in-one system: The system is pre-wired and pre-tested at the factory. Only the PV, AC, and communication main cables need to be connected on-site. Commissioning takes approximately 1–2 hours.

Modular system: Each component is installed independently. On-site work includes DC wiring, CAN/RS485 communication configuration, and protection parameter settings.

Difference in labor hours: Installation time for an all-in-one system is approximately 30%–50% of that required for a traditional modular system. The difference becomes more significant in large-scale projects.

However, stackable modular designs have advanced rapidly in recent years.

In OLINK’s stackable design, the battery modules are plug-and-play. Adding modules does not require the communication or protection parameters to be reconfigured. Its installation complexity is already very close to that of an all-in-one system.

Expansion Flexibility

Scalability is the primary advantage of modular systems.

The capacity and power of most all-in-one systems are fixed. A small number of models support limited expansion, such as adding another 5–10 kWh. However, expansion is restricted by the inverter and voltage platform, and the system eventually reaches its maximum capacity.

All-in-one system: Expansion capability is limited. Usually, only one or two expansion packs can be added. Beyond that limit, the complete system may need to be replaced.

Modular or stackable system: Capacity can be increased module by module, such as from 10 kWh to 15 kWh, 20 kWh, or 30 kWh, provided the inverter has sufficient capacity.

Significance for EV applications: When upgrading from one EV to two EVs or from 7 kW to 11 kW charging, a modular system may not require the core equipment to be replaced.

OLINK’s stackable modules use a standardized design. Every module has the same capacity and standardized interfaces.

Customers can initially purchase the basic capacity and add more modules six months later when a second EV is introduced. The modules are plug-and-play, making expansion highly convenient.

Output Power and EV Charging Compatibility

In EV charging applications, output power deserves more attention than battery capacity.

Many customers focus only on kWh and overlook kW. As a result, they install a high-capacity but low-power energy storage system.

When the 7 kW EV charger starts, the system immediately reaches its maximum output. Other household appliances must then draw electricity from the grid, preventing the energy storage system from delivering its full value.

7 kW single-phase charging: An energy storage system with only 5 kW of output is insufficient, especially when household loads are included. A model with at least 7 kW of output is recommended.

11 kW or 22 kW three-phase charging: A three-phase energy storage system or multiple systems connected in parallel are required. Modular parallel configurations provide greater flexibility.

Power expansion: All-in-one systems are limited by the inverter installed in each unit, resulting in fewer high-power options. Modular systems can connect multiple units in parallel to increase total output power.

OLINK’s modular solutions support multiple systems connected in parallel. Their continuous output capability can increase with the system configuration, supporting EV charging applications at 11 kW, 22 kW, and even higher power levels.

Unit Cost and Project Pricing

The following cost breakdown explains why equipment price alone does not provide a complete comparison.

Equipment cost: The price per kWh of an all-in-one system is usually higher than that of modular battery packs because the inverter and management system are integrated.

Installation cost: All-in-one systems require fewer labor hours, reducing labor costs by approximately 30%–50%.

Expansion cost: A modular system only requires additional battery modules during future expansion. Expanding an all-in-one system may require the entire unit to be replaced, creating a higher sunk cost.

Maintenance cost: An all-in-one system provides unified warranty coverage through one supplier. A modular system may involve warranties from multiple suppliers.

Therefore, the calculation should consider total lifecycle cost rather than only the initial purchase price.

For small projects that will not require expansion, an all-in-one system may provide a lower total cost. For projects with expected growth, a modular system is usually more cost-effective over the long term.

Maintenance and After-Sales Complexity

After-sales maintenance is another factor that procurement teams can easily overlook.

All-in-one system: Customers work with one supplier and receive unified warranty coverage. However, the failure of an internal component may require the complete unit to be returned to the factory, resulting in longer downtime.

Modular system: A faulty module can be replaced independently without affecting the operation of other components, improving overall system availability.

Multi-brand modular system: When a traditional modular system combines several brands, customers may need to contact multiple suppliers for after-sales support. This increases communication and coordination costs.

A balanced solution is to select a stackable modular system from one brand, such as OLINK’s stackable solution.

It provides unified warranty coverage and a single after-sales contact while retaining the maintenance advantages of modular architecture. If one module fails, only that module needs to be replaced. The entire system does not need to be returned.

Installation Space Requirements

Space is an important consideration for residential and small commercial projects, especially in garages and equipment rooms where the available area is limited.

All-in-one system: A single cabinet has a small footprint. A vertical unit normally occupies approximately 0.3–0.5 square meters and can be installed against a wall.

Traditional modular system: The inverter, battery cabinet, and distribution box are installed separately. This requires more space and additional room for wiring.

Stackable modular system: Vertical stacking provides a footprint similar to that of an all-in-one system while allowing battery capacity to be increased.

Therefore, modular systems should not be rejected simply because space utilization is important.

A stackable system can occupy almost the same floor area as an all-in-one system while providing much greater capacity flexibility.

Three Special Considerations for EV Charging Applications

Returning to the specific requirements of EV charging, the selection logic differs from that of an ordinary residential energy storage system.

EV charging has unique power and capacity requirements. The following are the three most important considerations.

Charging Power Matching: Selecting a System for 7 kW, 11 kW, and 22 kW Charging

The power rating of the EV charger directly determines the required output power of the energy storage system.

The following provides a clear matching reference.

7 kW single-phase EV charger: This is the most common specification for residential charging. The energy storage system should provide at least 7 kW of continuous output while reserving another 2–3 kW for household loads. Therefore, an actual output of 8–10 kW provides a more reliable configuration. A single all-in-one system can support the application if its output power is sufficient.

11 kW three-phase EV charger: This specification is commonly used in villas and small commercial projects. It requires a three-phase energy storage system, with a recommended starting capacity of 15 kWh. Modular solutions provide more advantages in three-phase applications because parallel connection and future expansion are easier.

22 kW three-phase EV charger: This configuration is generally used in commercial projects with multiple parking spaces or for fleet charging. The energy storage system should provide more than 20 kW of output power. A modular parallel configuration is normally required because a single system may be unable to support the complete load.

If you are unsure how to configure a specific project, you can consult our technical team.

We will develop a solution based on the number of EV chargers, their power ratings, and the average daily charging duration.

Expansion Paths for Multi-Parking-Space and Multi-EV Applications

An increasing number of residential and small commercial projects face the same challenge: only one EV is currently in use, but a second or even third EV may be added within the next one or two years.

In this situation, the expansion path of the energy storage system becomes particularly important.

Starting with one EV but having a clear expansion plan: A basic modular system is recommended. Battery modules can be added later, while sufficient inverter capacity should be reserved from the beginning.

Uncertain whether another EV will be added: An all-in-one system can be selected initially, but its maximum expansion capability must be confirmed. Some all-in-one systems cannot be expanded, while others support one or two additional battery packs.

Commercial multi-parking-space projects: A modular stackable solution should be selected directly. Total capacity can be planned according to the number of parking spaces and charging power, allowing deployment and investment to be completed in phases.

One villa project we completed followed this path.

The customer initially owned only one Model Y and installed a 15 kWh all-in-one system. The customer later purchased an EQE and upgraded from one 7 kW charger to two chargers, making the original capacity insufficient.

Fortunately, the selected system supported expansion. Adding one expansion pack resolved the issue.

Capacity Expansion for Peak-Valley Electricity Price Arbitrage

If the project is located in a region with a significant difference between peak and off-peak electricity prices, such as Europe, Australia, or certain provinces in China, the energy storage system can be used for more than EV charging.

It can charge during off-peak periods and discharge during peak periods to reduce electricity costs.

EV charging only: Capacity can be configured based on daily driving energy demand multiplied by approximately 1.2–1.5.

EV charging plus peak-valley arbitrage: Capacity must cover the combined total of EV charging demand and peak-period household electricity consumption. The required capacity is normally 30%–50% higher than that of an EV-charging-only application.

Advantages of modular systems: Modular architecture provides a clearer advantage in arbitrage applications. Capacity can be adjusted according to local electricity pricing policies, allowing more battery modules to be added when the potential savings are greater.

Calculating the return on investment and optimizing capacity for peak-valley electricity price arbitrage requires professional analysis.

If required, we can conduct an ROI assessment to determine which capacity offers the shortest payback period.

Selection Decision Tree: Quickly Evaluate Your Project

After reviewing these comparisons, how should you make the final selection?

The following decision logic allows you to evaluate the most suitable option according to your project conditions.

One EV + 7 kW Charging → An All-in-One System Is Sufficient

Conditions: Only one residential EV, an EV charger rated at 7 kW or below, and no clear plan to add a second EV within the next one or two years.

Recommended solution: An all-in-one system with 10–15 kWh of capacity and 7–10 kW of output power.

Reason: Fast installation, controllable cost, and simple operation and maintenance. It can fully support daily charging for one EV and residential backup power requirements.

Two EVs + Future Expansion → A Modular System Provides Greater Flexibility

Conditions: Two EVs are already in use, or there is a clear plan to add a second EV within one year. Charging power is between 7 kW and 11 kW, and the investment will preferably be divided into phases.

Recommended solution: A modular stackable system starting at 15–20 kWh, with expansion capacity reserved for 30 kWh or more.

Reason: Purchase the initial capacity first and add modules when necessary. This avoids excessive initial investment while allowing the system’s power to be upgraded accordingly.

Commercial or Multi-Parking-Space Projects → Modular Stackable Systems

Conditions: Three or more EVs, 11 kW or 22 kW charging, centralized charging across multiple parking spaces, or a project that may be constructed in phases.

Recommended solution: A modular energy storage system supporting multiple units connected in parallel. Total capacity should be calculated according to the number of parking spaces multiplied by the charging energy required per vehicle.

Reason: Commercial projects require higher capacity and power and often need phased construction. Modular architecture offers a clear total cost of ownership advantage.

Still unsure? Send us your project information. Our solution team will provide a tailored system selection recommendation and quotation within 24 hours.

A Third Option: Stackable Integrated Design

You may have noticed that traditional all-in-one and modular systems both have advantages and limitations. Choosing either architecture involves certain compromises.

Is there a solution that combines the installation convenience of an all-in-one system with the expansion flexibility of a modular system?

Yes. This is OLINK’s stackable integrated design.

Installation is as simple as an all-in-one system: The base unit, which contains the inverter and control unit, is combined with stackable battery modules in a vertical installation. Only the main cables and stackable modules need to be connected on-site, reducing connection points and commissioning time.

Expansion is as flexible as a modular system: The battery modules are standardized and plug-and-play. The BMS and communication settings do not need to be reconfigured. Adding one module increases the system capacity by one level.

Unified inverter control: All battery modules share one inverter and energy management system, providing high system efficiency, low communication latency, and unified protection logic.

Unified warranty contact: The complete system is manufactured by OLINK. Regardless of which module experiences a problem, customers only need to contact the OLINK after-sales team instead of coordinating with multiple suppliers.

The core concept behind OLINK’s stackable design is to keep the complexity of modular architecture inside the factory while providing simplicity to customers and installers.

Every battery module is calibrated and matched before leaving the factory. After the modules are stacked on-site, the system identifies and configures them automatically without requiring manual parameter settings.

This design is particularly suitable for EV charging applications.

A customer can begin with one EV and 15 kWh of capacity, then add another module to reach 30 kWh when a second EV is purchased. The inverter does not need to be replaced, the wiring does not need to be modified, and the expanded system can be used immediately.

If you would like to explore the technical details of these residential energy storage systems, you can visit our product page for detailed specifications and application cases.

OLINK Product Solutions

After explaining the selection logic, we can now return to OLINK’s product portfolio.

Many industry partners ask whether our stackable solution should be classified as an all-in-one or modular system. The following explains our product positioning and suitable application scenarios.

15 kWh All-in-One Solution

Our 15kWh all-in-one energy storage system is a primary model for residential single-EV applications.

Battery capacity and chemistry: 15 kWh LFP battery with a cycle life of more than 6,000 cycles.

Output power: Integrated hybrid inverter with 7–10 kW output, supporting a 7 kW EV charger and household loads simultaneously.

Installation method: Supports wall-mounted or floor-standing installation, with a footprint of less than 0.5 square meters.

Intelligent management: Built-in BMS and EMS, supporting remote app monitoring and peak-valley electricity price settings.

Certifications: Certified to IEC 62619, CE, and other applicable requirements for the EU and most international markets.

This model is particularly suitable for distributors and installers that require standardized, large-scale delivery.

It reduces training costs, increases installation efficiency, and simplifies after-sales support.

30 kWh Modular Stackable Solution

For multi-EV households and small commercial projects, our 30kWh modular battery storage system is a more suitable choice.

Stackable architecture: Uses OLINK’s stackable design, starting with one module and allowing additional modules to be added as required. The system supports expansion to 30 kWh and above.

Three-phase output: Provides 11–20 kW+ of output power and supports 11 kW and 22 kW EV charging applications.

Plug-and-play expansion: Battery modules can be added without professional commissioning. Installation teams can operate the system after basic training.

Parallel operation: Supports multiple systems connected in parallel and can be expanded to higher capacities for commercial multi-parking-space projects.

Unified after-sales service: Provides unified warranty coverage and after-sales service for the complete system, avoiding the compatibility and after-sales coordination issues associated with traditional multi-brand modular systems.

OEM/ODM Customization and Large-Volume Delivery Capabilities

As an energy storage manufacturer with its own factory, OLINK provides standard products as well as OEM and ODM customization services.

Production capabilities: OLINK’s production base in Huizhou provides vertical integration capabilities from battery cells to complete systems. Its monthly production capacity can support large-volume orders.

Customization support: Appearance, functions, and communication protocols can be customized to meet the specific requirements of different brands and markets.

Quality control and certifications: Full-process quality control is supported by an ISO 9001 quality management system. Products are certified to IEC 62619, CE, UN38.3, and other international standards.

Technical support: A professional technical support team provides assistance throughout the process, from solution design to installation training, helping partners expand their markets efficiently.

If you are looking for a reliable supplier of home battery storage systems, you are welcome to contact us for either standard product procurement or OEM customization.

Common Selection Mistakes and Risk-Avoidance Recommendations

After completing numerous projects, we have seen many common system selection mistakes. The following recommendations can help you avoid them in advance.

Comparing unit prices instead of total cost

All-in-one equipment may be more expensive but requires less installation labor. Modular equipment may have a lower purchase price but require more labor, while future expansion costs also differ. Price comparisons should consider total lifecycle cost rather than only the equipment price per kWh.

Underestimating future EV growth

Many customers believe they will only own one vehicle. Two years later, both partners may own an EV, and another may be purchased for a child. An energy storage system may operate for more than ten years, making growth in the number of EVs highly likely. Reserving some additional capacity is therefore advisable.

Ignoring installation space and floor load capacity

All-in-one and stackable energy storage systems are both heavy, with individual units often weighing between one and two hundred kilograms. The installation location must account for structural load capacity, transportation access, ventilation, and heat dissipation rather than only battery capacity.

Assuming that modular systems are always difficult to install

This is an outdated assumption. The installation complexity of a new-generation stackable modular design is already similar to that of an all-in-one system. These systems have fewer connection points, automatic module identification, and simplified commissioning. Do not allow an outdated perception to prevent you from selecting a more suitable solution.

Considering capacity but ignoring power

EV charging requires continuous high-power discharge. Combining 20 kWh of capacity with only 5 kW of output is like connecting a large water tank to a narrow tap. The stored energy cannot be delivered quickly enough, regardless of total capacity. Both kW and kWh must be considered during system selection.

FAQ

Q: What Is the Main Difference Between All-in-One and Modular Home Energy Storage for EV Charging?

A: All-in-one systems integrate the battery, inverter, and BMS into a single cabinet. They can be installed within 1–2 hours and are suitable for single 7 kW EV charging applications.

Modular stackable systems can scale from 10 kWh to more than 30 kWh through incremental battery modules. They support 11–22 kW multi-EV charging while reducing future expansion costs.

OLINK offers both architectures, including stackable integrated designs.

Q:  How Much Power Output Do I Need for a 7 kW EV Charger with Household Loads?

A: For a 7 kW single-phase EV charger plus household loads, which typically require 2–3 kW in the evening, choose a home energy storage system with at least 8–10 kW of continuous output.

A 15 kWh all-in-one system with 7–10 kW output generally supports a single-EV household. A 20–30 kWh modular system is more suitable for multi-EV households.

Q: Can I Expand an All-in-One Energy Storage System Later for a Second EV?

A: Most all-in-one systems have limited expansion capacity, typically allowing an additional 5–10 kWh.

For a second EV or an upgrade to 11 kW or higher charging, modular stackable systems are more suitable. Battery modules can be added incrementally without replacing the inverter.

OLINK’s stackable design supports plug-and-play module expansion to 30 kWh and above.

Q: Which Is More Affordable: All-in-One or Modular Home Energy Storage?

A: An all-in-one system has a higher equipment cost per kWh but can reduce installation labor costs by 30%–50%. This can make it more economical for small projects with fixed capacity requirements.

Modular systems may have lower equipment costs but require more initial installation labor. However, they can reduce long-term upgrade costs by up to 40% compared with replacing an all-in-one unit.

The final total cost depends on the project scale and future growth plans.

Q: What Certifications Should I Consider When Sourcing Home Energy Storage Systems?

A: Key certifications include IEC 62619 for battery safety, CE for EU market compliance, UN38.3 for transportation safety, and ISO 9001 for quality management.

OLINK’s Huizhou factory produces systems certified to IEC 62619, CE, and other international standards, supported by quality control throughout the production process.

Conclusion

There is no universally right or wrong choice between an all-in-one and a modular system. The correct choice depends on whether the architecture is suitable for the project.

One EV, 7 kW charging, and no planned expansion: Choose an all-in-one system for simpler installation and more controllable costs.

Multiple EVs, 11 kW or higher charging, and expected future growth: Choose a modular stackable system for a better long-term total cost of ownership.

Need the advantages of both architectures: Choose OLINK’s stackable integrated design for simplified installation, flexible expansion, and unified after-sales support.

As a Huizhou-based ev charging equipments and residential energy storage manufacturer, OLINK operates its own factory and maintains a complete quality control system.

The company has obtained ISO 9001, IEC 62619, CE, and other certifications. Whether you require standard products or OEM customization, we can provide reliable products and professional technical support.

If you are currently working on an energy storage project supporting EV charging, you are welcome to send your project requirements to our OLINK solution team.

We will provide a tailored system selection recommendation and quotation within 24 hours.