How to choose the best inverter for off grid solar system

Off-grid solar systems are an excellent way to harness the power of the sun and gain energy independence. When setting up such a system, one of the most critical components you'll need is an inverter.

Solar inverters are responsible for converting the direct current (DC) electricity produced by your solar panels into alternating current (AC) electricity, which is what your household appliances and devices use.

In this blog post, we'll delve into the key features and considerations for choosing the best inverter for your off-grid solar system.

 

 

Inverter sizing for solar system

Determining Inverter Rated Based on Your Power Requirements

Before selecting an inverter, you need to determine your power requirements. This involves assessing both your daily energy consumption and peak load.

• Daily Energy Consumption
  Calculate your daily energy consumption by listing all the appliances and devices you plan to power with your solar system. Note the wattage of each item and how many hours you expect to use them per day. This will give you an estimate of your daily energy needs.
• Peak Load Analysis
  Peak load analysis is crucial to ensure your inverter can handle the occasional high power demands of certain appliances, especially those with motors like refrigerators and pumps. Take note of the surge power requirements of inductive loads (such as motors and air conditioners) in order to appropriately size the inverter.

 

Matching the Inverter with Your Solar Power System

The inverter plays a pivotal role in converting the direct current (DC) electricity generated by your solar panels into alternating current (AC) electricity usable in your home. IBefore purchasing an inverter, it is important to read the product specification to ensure that the inverter aligns perfectly with the specific requirements of your solar array, battery system, and AC integration.

 

AC Integration

Firstly, the inverter should seamlessly integrate with your home's AC system. Consider these factors:

• Inverter Output Capacity
  The inverter's AC output capacity should align with your household's electricity demands. Oversizing or undersizing the inverter can affect system performance and efficiency.
• Compatibility with Household AC Voltage and Frequency
  The inverter's output voltage and frequency must match your local grid standards to avoid damaging appliances or encountering compatibility issues.

 

Battery System

It's vital to consider the inverter's compatibility with the battery's DC output. This compatibility is determined by:

• DC Output Voltage
  When incorporating a storage battery into your solar setup, it's crucial to specify the DC input voltage for your inverter. Common options include 12V, 24V, 36V, and 48V.
• Battery Type Compatibility
  Inverters are designed to work with specific battery types, such as lead-acid, lithium-ion, or other emerging technologies. Ensure that your inverter is compatible with your chosen battery technology.

 

Solar Array

Lastly, If your inverter comes with a built-insolar charge controller, it must be in harmony with the solar array's specifications.

For an in-depth understanding of selecting the right solar charge controller, it's highly recommended that you read the this choosing guide.

• Max PV Input Power
  The inverter's maximum power-handling capacity must match or exceed the total power output of your solar array. Choosing an inverter with a lower rating will result in wasted potential energy.
• PV Input Voltage Range
  The inverter's input voltage range must correspond to the voltage generated by your solar panels. An inverter with a flexible input voltage range can adapt to varying weather conditions and maximize energy conversion.

 

Different Inverter Types for Off-Grid Solar Systems

In this section, our primary focus is on inverters designed for off-grid solar systems. To delve deeper, please click the link to learn more about the various types of solar inverters available.

 

Catergorize By Waveform of the output current

Two primary inverter types are crucial in this context, each distinguished by the waveform of their output current: Pure Sine Wave Inverters and Modified Sine Wave Inverters.

• Pure Sine Wave Inverter
  Pure sine wave inverters produce a smooth, high-quality AC output similar to utility power. They are ideal for most solar systems, ensuring compatibility with sensitive electronics and appliances.
• Modified Sine Wave Inverter
  Modified sine wave inverters offer a more affordable option but produce a less refined AC output. While suitable for many applications, they may not be ideal for sensitive equipment.

Due to the versatility and compatibility of pure sine wave inverters, they are now the best choice for the majority of photovoltaic systems.

 

Classify by Inverter power supply

Next, let's categorize inverters based on their power source. They can be primarily divided into two types:

 

Power Inverter

A power inverter, also known as a battery inverter, is designed to convert the direct current (DC) from batteries into alternating current (AC) for your household appliances. They are commonly used in conjunction with solar charge controllers and find extensive application in completely off-grid solar power systems for RVs, boats, trucks, and more, ensuring a reliable power source, primarily sourced from batteries.

 

Off-Grid Hybrid Inverter/Inverter Charger

Hybrid inverter, commonly referred to as inverter chargers, are advanced power converters that seamlessly integrate multiple power sources. They convert DC to AC and enable input from backup generators or the grid, thanks to the built-in solar charge controller and AC charger, which allows them to recharge the battery bank when connected to an external AC power source, such as a generator or grid power.

Moreover, they support the configuration of charging and discharging priorities between power sources, making them a comprehensive solution for off-grid setups that may have intermittent grid connections. This ensures a seamless power supply and efficient battery charging capabilities.

The hybrid inverter offers a wide range of features. It is essential to grasp the inverter's key attributes before choosing an off-grid solar system, enabling you to make informed decisions tailored to your specific requirements.

 

Extra Inverter Features for Off-Grid Solar Systems

Taking PowMr inverters as an example, the features that influence your purchase decision are introduced below.

 

Single Phase vs. Split Phase vs. Three Phase

Single phase, split phase, and three-phase are three distinct electrical power distribution systems.

Single-phase, the simplest and common, has two conductors for residential and small commercial use, providing either 120 or 230 volts.

Split-phase, commonly used in North America, especially in the United States and Canada, is a variation with three conductors. It delivers 120 volts between each live and neutral and 240 volts between live wires for larger appliances.

Explainer Video on Split Phase Inverter

 

Three-phase power is a more complex system commonly used in industrial and commercial settings. It consists of three live (hot) wires and one neutral wire, although the neutral is often omitted in certain industrial applications. The voltage levels can vary, with common configurations being 208V, 240V, 480V, or higher.

 

Parallel Capability

A parallel inverter is a device that synchronizes multiple inverters via a shared communication bus to combine their outputs for meeting home or facility power requirements.

This feature is essential for off-grid systems that may need to grow over time. It allows you to add more solar panels and inverters as your energy needs increase, making it cost-effective and scalable.

 

Peak Shaving & Valley Filling

Peak shaving is a feature that helps reduce the cost of electricity in areas with time-of-use pricing. It involves storing excess energy generated during off-peak hours and using it during peak demand periods. This can significantly lower your electricity bills by avoiding high peak-hour rates.

Comprehensive Video Explanation of Time-of-Use Charging and Discharging

 

Number of MPP Trackers

Understanding the number of MPP trackers is vital when you have multiple solar arrays with different orientations. It ensures that your inverter optimally harvests energy from various panels, increasing overall system efficiency and energy production.

For smaller systems or those with a single string of solar panels, a single MPP tracker may suffice.

However, larger systems with multiple strings or panels facing different orientations benefit from inverters with multiple MPP trackers. These trackers improve the efficiency and performance of the system, ensuring you harness the maximum energy from your solar panels, especially in situations with shading or varying panel conditions.