Learn more about off-grid inverters for solar and wind

FAQ about off-grid inverters

What types of off-grid inverters are available?

There are several types of off-grid inverters available, and the most common types include:

  1. Stand-alone Off-Grid Inverter: This type of inverter is designed to work independently in an off-grid system without any connection to the utility grid. It converts DC electricity from batteries or other renewable energy sources into AC electricity for powering household appliances and other AC loads. Stand-alone off-grid inverters usually have built-in charge controllers to manage the charging and discharging of batteries, and they may also have additional features such as voltage and frequency regulation, protection mechanisms, and monitoring capabilities.
  2. Hybrid Off-Grid Inverter: A hybrid off-grid inverter is a versatile type of inverter that can work in both off-grid and grid-tied systems. It can be connected to both renewable energy sources (such as solar panels or wind turbines) and the utility grid, allowing for seamless transition between grid-connected and off-grid operation. Hybrid off-grid inverters typically have advanced features such as grid-forming capabilities, battery management systems, and multiple operating modes, which provide greater flexibility and control over the system’s performance.
  3. Grid-Interactive Off-Grid Inverter: Also known as grid-parallel or grid-assist inverters, these inverters are designed to work in conjunction with the utility grid in an off-grid system. They allow for energy to be fed back into the grid when the renewable energy sources produce excess electricity, and they can also draw energy from the grid when the renewable sources are not generating enough electricity to meet the demand. Grid-interactive off-grid inverters typically have grid-tie functionality, which means they can synchronize with the utility grid’s voltage and frequency, and they may also have battery charging and discharging capabilities.
  4. Mobile Off-Grid Inverter: This type of inverter is designed for portable or mobile off-grid applications, such as RVs, boats, or camping. They are compact, lightweight, and usually come with built-in charge controllers and protection mechanisms to ensure safe and efficient operation in mobile environments. Mobile off-grid inverters may have lower power capacities compared to other types of off-grid inverters, but they are designed for mobility and ease of installation in temporary or mobile setups.
  5. Multi-mode Off-Grid Inverter: Multi-mode off-grid inverters are a type of hybrid inverter that can work in multiple modes, such as grid-tied, off-grid, and hybrid modes, providing maximum flexibility in different operating conditions. They are capable of switching between different modes automatically or manually, depending on the system’s requirements and the availability of energy sources. Multi-mode off-grid inverters are suitable for more complex off-grid systems that may need to operate in different modes depending on the changing energy conditions or user preferences.

It’s important to select the right type of off-grid inverter that matches your specific requirements and system configuration. Consulting with a qualified professional or an experienced installer can help you determine the best type of off-grid inverter for your particular off-grid system.

Grid forming off-grid inverter

A grid-forming off-grid inverter is a specialized type of power inverter that is capable of forming its own AC grid or microgrid in an off-grid or isolated electrical system. Unlike traditional inverters that require an external grid or AC source to establish voltage and frequency references, grid-forming inverters have the ability to autonomously generate stable AC voltage and frequency, allowing them to act as the primary power source in an off-grid system.

Grid-forming off-grid inverters typically have advanced features that enable them to operate in standalone mode without relying on an external grid, making them suitable for use in remote areas where there is no access to the utility grid or in situations where grid connection is not desired. They are designed to work with various energy sources, such as renewable energy systems like solar panels, wind turbines, or hydroelectric generators, as well as energy storage devices like batteries or other energy management systems.

One of the key features of grid-forming off-grid inverters is their ability to regulate the voltage and frequency of the AC output to ensure stable and reliable power supply to the loads in the electrical system. They are capable of forming their own AC grid, which allows them to maintain stable voltage and frequency within predetermined limits, even in the absence of an external grid. This grid-forming capability is essential for maintaining reliable operation of sensitive loads, such as electronic devices, motors, and appliances.

Grid-forming off-grid inverters may also have advanced communication and monitoring capabilities, allowing for remote control, monitoring, and integration with other components of the off-grid system, such as renewable energy sources, energy storage systems, and load management devices. This allows for efficient energy management, system monitoring, and integration with smart grid or remote management systems.

Grid-forming off-grid inverters are typically used in more complex off-grid systems, such as microgrids, remote communities, or industrial applications, where reliable and autonomous power supply is required. They provide greater control, flexibility, and stability to off-grid electrical systems, and are often used in conjunction with other components, such as renewable energy sources, energy storage systems, and load management devices, to create reliable and sustainable off-grid power solutions. As grid-forming technology continues to advance, it holds great potential for enabling more sophisticated and advanced off-grid power systems in the future.

Stand alone off-grid inverter

A standalone off-grid inverter, also known as a standalone or stand-alone inverter, is a type of power inverter that is designed to work independently in an off-grid or isolated electrical system without any connection to an external utility grid. It converts DC (direct current) power from energy sources such as batteries, solar panels, wind turbines, or hydroelectric generators into AC (alternating current) power that can be used to power AC loads.

Standalone off-grid inverters typically have built-in features that enable them to function without relying on an external grid, making them suitable for use in remote areas where there is no access to utility power, or in situations where grid connection is not desired or not available. They are commonly used in off-grid systems such as remote cabins, RVs, boats, and other applications where autonomous power supply is required.

Here are some key features of standalone off-grid inverters:

  1. Battery Charging: Standalone off-grid inverters are typically capable of charging batteries, which store excess energy generated by energy sources like solar panels or wind turbines. They usually have built-in battery chargers that can efficiently charge the batteries from the DC energy generated by the energy sources, allowing for energy storage and use during times when the energy sources are not producing enough power.
  2. AC Output: Standalone off-grid inverters convert the DC power from the energy sources into AC power that can be used to power AC loads, such as household appliances, tools, or other electrical devices. They usually provide a stable and reliable AC output with the appropriate voltage and frequency to power the loads in the off-grid system.
  3. System Monitoring and Protection: Standalone off-grid inverters often come with built-in monitoring and protection features that help to ensure the safe and efficient operation of the off-grid system. These features may include over-voltage protection, over-current protection, short-circuit protection, and temperature protection, among others. They may also have monitoring capabilities, such as LED displays or communication interfaces, to provide information about the system’s performance, battery status, and other parameters.
  4. Load Management: Some standalone off-grid inverters may also have load management features, allowing for prioritization or control of loads based on their importance or energy availability. This can help optimize the use of available energy and prevent overloading of the system.
  5. System Integration: Standalone off-grid inverters can be integrated with other components of an off-grid system, such as energy sources, batteries, charge controllers, and other devices, to create a complete off-grid power solution. They may have communication interfaces or protocols that allow for remote control, monitoring, and integration with other system components, enabling efficient energy management and system operation.
  6. Inverter Efficiency: The efficiency of a standalone off-grid inverter is an important factor to consider, as it can affect the overall performance and effectiveness of the off-grid system. Higher efficiency inverters are generally preferred, as they can convert more of the DC energy from the energy sources into usable AC power, reducing energy losses and maximizing the available power for use in the loads.

Standalone off-grid inverters come in different sizes, capacities, and specifications to suit various off-grid power system requirements.

What voltage should i use in an off-grid power system?

The voltage to be used in an off-grid power system depends on various factors, including the specific requirements of your power system, the type of loads you want to power, the capacity of your energy sources (such as solar panels or wind turbines), and the distance between the energy sources and the loads. Here are some common considerations for determining the appropriate voltage for your off-grid power system:

  1. Load Requirements: Consider the voltage requirements of the loads you want to power in your off-grid system. Different appliances and equipment may have different voltage requirements, and it’s important to choose a voltage that matches the majority of your loads to ensure compatibility. For example, in North America, most household appliances are designed to run on 120V or 240V AC, while in other parts of the world, different voltages may be standard.
  2. Energy Source Capacity: The capacity of your energy sources, such as solar panels or wind turbines, can also influence the voltage of your off-grid power system. Higher voltage systems are often used for larger energy sources with higher capacity, as they can reduce energy losses over long distances and minimize voltage drop. However, lower voltage systems may be more appropriate for smaller energy sources with lower capacity.
  3. Distance and Wiring Considerations: The distance between your energy sources and loads, as well as the type and length of wiring used, can affect the voltage of your off-grid system. Higher voltages may be necessary for longer distances or higher power loads to minimize losses due to resistance in the wiring. It’s important to consult with a qualified professional or use appropriate sizing tools to determine the right wire gauge and voltage for your specific system to ensure efficient and safe operation.
  4. System Efficiency and Safety: Higher voltage systems can sometimes be more efficient in terms of reducing energy losses during transmission and distribution, but they may also pose higher safety risks, such as increased risks of electrical shock or fire hazards. It’s important to consider the safety implications of the voltage chosen for your off-grid system and ensure that it meets local electrical codes and safety standards.

Common voltage options for off-grid power systems include 12V, 24V, 48V, and higher voltages depending on the system size and requirements. Lower voltage systems (such as 12V or 24V) are commonly used in smaller off-grid systems with lower power demands, such as small cabins or RVs, while higher voltage systems (such as 48V or higher) are often used in larger off-grid systems with higher power demands, such as remote homes or industrial applications.

Selecting the appropriate voltage for your off-grid power system requires careful consideration of various factors, and it’s recommended to consult with a qualified professional or an experienced installer to determine the best voltage option for your specific needs and requirements.

How is an off-grid inverter different from a grid-tied inverter?

A grid-tied inverter takes DC power from solar panels, turns it into AC, and sends it into the grid for credit. Grid-tied inverters are simpler and easier to wire since there are usually only two main components—the inverter itself and your solar panels. (Some grid-tied systems are starting to incorporate energy storage, but most don’t have any batteries at all.)

But an off-grid inverter needs a battery bank to function.

Here’s how it works: your solar panels feed DC power into the batteries. Then your inverter takes that power and “inverts” it, creating AC power for your home. This works essentially like a miniature power grid.

(In case you’re curious, no, your inverter won’t deplete your batteries provided your system is set up and designed right. The battery bank gets recharged by your solar panels and a charge controller, and by a backup generator in the winter months.)

As you might imagine, off-grid systems are more complicated, thanks to additional components like the charge controller, battery monitor, and additional AC and DC circuit breakers. All of these things tend to make off-grid systems more difficult to wire and install. It can also be a challenge to buy off-grid equipment because there are a lot of associated accessories: remote controls, battery monitor, breakers and enclosures, surge suppressors, and so on.

Picking the right parts can be confusing enough—but there’s no more critical decision than buying the right inverter.

How to Pick the Best Off-Grid Inverter?

The first thing to think about is how much power you need. Fortunately, sizing off-grid inverters is straightforward if you know what appliances you’re going to use. Add up the wattage of all your lights and appliances to calculate the number of watts you’d need if everything was used all at once. (No, you’re not likely going to use everything, but this is an easy way to be safe.)

Don’t forget to consider the voltage—although most appliances run on 120Vac, some appliances, such as well pumps, require 240Vac. Example: Let’s say you need 1,000 watts for your fridge, 500 watts for lights, and 200 watts for your phone & TV. That adds up to 1,700 watts. In this case, we’d suggest a minimum inverter size of at least 2,000 watts to give you a little extra headroom. (After all, you may add appliances in the future.)

What are the common off-grid solar inverter sizes?

What is the most popular size we sell in our inverter store? 4kW followed by 10kW. Different models and brands are available in various sizes and most of them can be stacked together for higher power output.

  • 1kW or less: are ideally suitable for small, part-time cabins for things like lights, phone charger and other small appliances in your cabin or home
  • 1kW – 2kW: small cabins with lights, phone, TV and a fridge.
  • 2kW – 4kW: cabins and small, energy efficient homes
  • 4kW – 10kW: most of off-grid home in Europe and USA, capable of powering most of the residential well pumps as well.
  • 10kW – 16kW: larger off-grid homes, farms, ranches and small commercial buildings, shops.
  • 16kW +: commercial building and larger homes, mansions.

Which to consider: pure sine wave instead of modified sine wave?

ou may hear some manufacturers talk about pure sine wave inverters. You don’t need to understand exactly how these work—it’s enough to know that the power that’s put out by a pure sine wave inverter is “cleaner” than what you’d get from a modified sine wave inverter.

Pure sine wave inverters deliver higher quality power output, similar to (or better than) our power grid. Modified sine wave inverters are cheaper, but they deliver lower-quality power output.

For this reason, modified sine wave inverters can cause issues with certain appliances. Motors, pumps and compressors run hotter and wear out more quickly. Certain sensitive appliances like computers can be damaged, or they may not work at all. These inverters also typically cause background noise on a stereo, and reduced video and audio quality for certain TVs.

That’s why we don’t recommend modified sine wave inverters for most applications; most of our off-grid customers are use pure sine wave inverters to avoid these potential issues.

Need a quick way to tell the difference? Look at your inverter’s total harmonic distortion (THD) rating. THD is an indicator of power quality output and will be listed on the spec sheet of any decent inverter.Rule of ThumbTo avoid running into trouble, choose a pure sign wave inverter with THD of 5% or less.

What elso to consider when choosing an off-grid inverter?

Look at the Technical Specs

Here are some other technical specs to consider:

  • Efficiency. This is a measure of how much power from the batteries your inverter delivers to your home when it’s operating in perfect conditions. A good peak efficiency rating is around 94% to 96%.
  • Self-consumption, or no-load current draw. How much power will your inverter consume just sitting there? Obviously you want this to be as low as possible.
  • Surge capacity. How much short-term overload can the inverter handle before it “trips?” Some appliances, like pumps or fridges, need as much as 2x–3x their running power to start up.
  • Battery charger output. Many off-grid inverters include a battery charger, which is used to recharge your batteries during the winter months with a backup generator. The battery charger will have a rating, usually measured in amps. Most decent off-grid inverters will have a battery charger in the range of 50-100 amps DC.
  • Temperature range. Inverters are sensitive to extreme heat. Pay careful attention to the temperature range if you plan on installing your system in your garage or anywhere it could be exposed to temperature extremes.
  • Warranty. Warranties start at 1 year and typically range from 3-5 years, with a few manufacturers offering a 10 year warranty extension option.

You can normally find information on all these features on the product spec sheets. Check with your solar tech for help comparing and picking the right inverter.

Research Features

Your inverter may need special features. Look into these ones:

  • Battery charger. A charger allows your system to be charged from a backup AC generator. Most bigger inverters include this; these are called “inverter/chargers.”
  • Grid-tied capability. Some off-grid inverters have the added capability of feeding power into the grid, here are a few examples:
    • Victron Quattro or the Victron Multiplus
    • Outback FXR/VFXR
    • Outback Radian
    • SMA Sunny Island

    This capability is useful if the grid becomes available in the future, or if you are setting up a grid-tied system with battery backup.

  • Automatic generator start. Usually you’ll need an add-on accessory for this, although some inverters or charge controllers can take care of it.

Read up on the manufacturer

Knowing about the inverter manufacturer is also important. Check into their history and reputation. Off-grid inverters need to be on all day, 365 days a year, for several years at a time—so you’ll want to choose one from a manufacturer with a reputation for reliability.

In our experience, there are only a handful of companies making high quality inverters for this purpose:

Do not forget price!

You also need to look at the price of the inverter system (including all required components)—as well as the features you get for that price. Make sure to compare the price of all required components, including the remote control, circuit breakers, mounting plate, and anything else required to install the system.

Learn more about off-grid living on the Off-Grid Blog and check our Solar PV Blog!

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