In South Africa, loadshedding leaves many without power for extended periods. This highlights the crucial need for backup power systems to essential operations can continue during power outages. However, there is often a debate over whether low-voltage backup systems or high-voltage backup systems are the better choice.
Written by Arno Odendaal, Senior Technical Sales Engineer at Menlo Electric South Africa
The difference between high-voltage and low-voltage battery systems is based on the voltage range of the batteries. A high-voltage battery system typically operates at voltages greater than 100V DC, while a low-voltage battery system typically operates at voltages less than 60V DC.
High-voltage battery systems are commonly used in electric vehicles, where the high voltage allows for more efficient power transfer and the ability to use smaller, lighter wiring. They also allow for faster charging times and greater energy storage capacity.
On the other hand, low-voltage battery systems are commonly used in smaller portable devices such as mobile phones, laptops, and handheld tools. They generally have a lower capacity and power output but are more cost-effective and easier to implement in smaller devices.
Low-voltage Residential Backup Systems
Low-voltage residential backup systems are typically based on DC technology and are usually installed as a battery backup for solar power systems or as a standalone system. These systems generally range from 24V to 48V DC and provide power for essential household appliances during a power outage.
Pros
Lower voltage inverters and batteries tend to be less expensive than high-voltage systems
Low-voltage systems are more flexible when it comes to installation options. This is because they typically have a lower minimum voltage requirement than high-voltage systems, which means they can work with a wider range of inverters
More efficient and cost-effective for smaller homes with low power consumption
Easy to install and maintain
Cons
Higher installation costs: The components needed for a low-voltage system can be more expensive, which can drive up installation costs.
Limited scalability: Low-voltage systems can also be more limited in terms of scalability, as they typically can’t be easily expanded beyond a certain point without significantly increasing the number of batteries required.
Less power output than high-voltage systems, which means they can only power essential appliances and not entire homes
Not suitable for high power consumption homes or commercial buildings
High-voltage Residential Backup Systems
High-voltage residential backup systems are typically designed to provide power to an entire home during a power outage. These systems usually operate at 230V AC and use a high-voltage battery, to provide power to the entire house. The high-voltage batteries used in these systems typically range from 100V to 600V DC and can provide reliable backup power when the main grid goes down.
Pros
Efficiency: High-voltage battery systems are generally more efficient than low-voltage systems, which can help reduce energy waste and increase cost savings over time. Lower internal resistance is one of the key advantages of using a high-voltage battery system. This means that the battery can deliver power more efficiently and with less waste heat, resulting in better overall performance and longer lifespan. Additionally, high-voltage battery systems have better thermal dynamics, meaning they can dissipate heat more effectively, which is important for preventing overheating and ensuring safe operation.
Smaller footprint: High-voltage battery systems require smaller cables and can have a smaller physical footprint compared to low-voltage systems.
Scalability: High-voltage battery systems can be more easily scaled up or down to accommodate changing energy needs.
Higher power output: High-voltage battery systems can deliver more power output compared to low-voltage systems, making them better suited for high-power applications.
More advanced technology: High-voltage battery systems often use newer, more advanced lithium-ion battery technology, which can provide longer lifespans and better performance compared to older low-voltage systems.
Cost-effectiveness: High-voltage lithium-ion battery systems may be more cost-effective than low-voltage systems. This is because the components required for a high-voltage battery system are generally less expensive than those required for a low-voltage system, such as DC busbars, cables, and fuses.
Cons
Higher component costs: High-voltage battery systems typically have higher battery and inverter costs compared to low-voltage systems.
Safety concerns: High-voltage battery systems can pose a safety risk if not installed and maintained properly. They may require additional safety features and precautions to mitigate this risk.
Limited compatibility: High-voltage batteries are not yet compatible with as many inverters as low-voltage batteries.
Environmental concerns: Like low-voltage systems, high-voltage battery systems rely on lithium-ion batteries, which can have environmental impacts if not disposed of properly. Additionally, the production of high-voltage batteries may require more energy and resources compared to low-voltage batteries.
Cost Comparison
The cost of a residential backup system can vary depending on a number of factors, such as the type and size of the system, the brand, and the location. However, as a general rule of thumb, high-voltage residential backup inverters and batteries tend to be more expensive than low-voltage inverters and batteries.
To give you an idea of the cost difference, a high-voltage system could cost around R150 000 to R200 000, while a low-voltage system may cost between R100 000 to R150 000. However, it’s important to note that the cost can vary depending on the specific components and installation requirements for each system. While the upfront cost of a high-voltage battery system may be higher due to the cost of the battery and inverter, the component costs like DC busbars, cables, and fuses are lower.
In addition to the initial cost of the system, it’s important to consider the ongoing costs of maintenance and replacement of components, such as batteries, which can be a significant expense over time. Additionally, high-voltage batteries are the newest technology, which means they offer advantages such as higher efficiency, longer lifetimes, and faster charging times. These factors should also be taken into consideration when evaluating the overall cost and benefits of a low-voltage versus high-voltage residential backup system.
It’s important to weigh the pros and cons of each system and consider factors such as power consumption, home size, and budget when deciding on which type of system is right for your needs.
Here’s a rough cost comparison:
A popular premium low-voltage inverter and MPPT all-in-one power solution – 48V 5000VA with a premium low-voltage 15kWh battery and 12 x 550W solar modules:
All-in-one inverter/MPPT: R55 000
Low-voltage 15kWh battery: R110 000
12 x 550W solar modules: R54 000 (assuming R4 500 per module)
Installation and miscellaneous costs: R30 000
Total cost: R249 000
A popular low-voltage more affordable 5KW hybrid inverter with a more affordable 14,3kWh battery and 12 x 550W solar modules:
5KW hybrid inverter: R29 000
Low-voltage14,3kWh battery: R87 000
12 x 550W solar modules: R54 000 (assuming R4 500 per module)
Installation and miscellaneous costs: R30 000
Total cost: R200 000
A premium high-voltage hybrid inverter with 15kWh of high-voltage batteries and 12 x 550W solar modules:
Premium high-voltage hybrid inverter: R25 000
Premium high-voltage batteries: R108 000
12 x 550W solar modules: R54 000 (assuming R4 500 per module)
Installation and miscellaneous costs: R30 000
Total cost: R217 000
It is important to note that these are rough estimates, and the actual cost may vary depending on factors such as location, installer fees, and availability of components.
Low-voltage vs high-voltage
Here are some reasons why someone might choose a low-voltage backup system:
Lower component costs: In general, the components for low-voltage systems are less expensive than those for high-voltage systems, which can make them more cost-effective for some users.
Easier installation: Low-voltage systems can be easier and less complex to install than high-voltage systems.
More options: Low-voltage systems have been around longer and there are more options available on the market. This means that there may be more choices available to suit specific needs and preferences.
Safety: Low-voltage batteries can be safer than high-voltage batteries in certain situations. Since low-voltage batteries typically operate at lower voltages, they may pose a lower risk of electrical shock or fire in the event of a malfunction or mishandling. However, it’s important to note that all batteries, regardless of voltage, can pose safety risks if not handled properly. It’s important to follow manufacturer guidelines and safety protocols when installing, using, and maintaining any type of battery system.
Greater compatibility: Low-voltage systems are generally more compatible with a wider range of solar panels, which can make them easier to integrate into existing solar setups.
Here are some reasons why someone might choose a high-voltage backup system over a low-voltage backup system:
More energy storage: High-voltage battery systems are typically larger and have more energy storage capacity than low-voltage systems, making them a good choice for larger homes or properties with higher energy demands.
Better efficiency: High-voltage systems can be more efficient due to the use of high-voltage batteries and inverters, which can reduce energy losses during conversion.
Futureproofing: High-voltage systems use newer technology and are likely to become more common in the future. Investing in a high-voltage system now may be a good way to future-proof your home or property.
Reduced installation costs: While the hardware for high-voltage systems can be more expensive, the installation costs may be lower due to the simplicity of the system and the reduced need for additional components.
High-voltage batteries can be safer than low-voltage batteries in some ways. For example, they require smaller wiring and connectors, which reduces the risk of electrical fires or short circuits. Additionally, high-voltage systems often have built-in safety features, such as circuit breakers and fuses, to help protect against overloading or other malfunctions. However, high-voltage batteries also pose their own unique safety risks, such as electrocution and the risk of explosion or fire if not installed and maintained properly. It’s important to follow all safety guidelines and manufacturer recommendations when working with high-voltage batteries.
In conclusion, both low-voltage and high-voltage residential backup systems have their pros and cons. Low-voltage systems are more cost-effective for smaller homes with low power consumption, are more flexible when it comes to installation options, and are easy to install and maintain.
On the other hand, high-voltage systems are more efficient, have higher power output, can be easily scaled up or down to accommodate changing energy needs, and often use newer, more advanced lithium-ion battery technology. High-voltage hybrid inverters, being relatively new in the market and employing advanced technology, have been designed to accommodate higher amperages from solar modules.
As the size of solar modules continues to increase, so does the amperage, and high-voltage hybrid inverters can handle this demand effectively. Low-voltage hybrid inverters were designed for use with smaller solar modules that were available at the time. With the introduction of larger solar modules, these inverters may not be able to handle the higher amperages that come with them, and as a result, may not be able to keep up with the evolution of solar technology.
When considering which system to choose, factors such as power consumption, building size, budget, future-proofing and ongoing maintenance costs should be taken into consideration. While high-voltage systems have a higher upfront cost, they offer advantages such as higher efficiency, longer lifetimes, and faster charging times, which could result in cost savings in the long run.
Ultimately, the choice between low-voltage and high-voltage residential backup systems depends on the specific needs and preferences of the user. It is important to carefully evaluate the pros and cons of each system and consult with a professional to determine the best fit for your situation.