How to select a solar inverter?


Whether you are setting up your new home or planning to restore old appliances, what are the most crucial decisions you should consider? If you have thought of installing a solar inverter, choosing the right one carries a lot of weight.

Installing a solar inverter is a long-term investment. Moreover, it is one of the key segments of a home solar power system. Hence, opting for the right one will let you sleep peacefully. However, among the sprawling number of brands and different categories, how would you land up for the right one?

Here, in this article, I will discuss all the crucial factors that impact your buying decision. I will also put light on the power requirement of your home appliances.

What are the different types of inverters?

An inverter converts Direct Current to Alternative Current. It consists of solar panels, a charge controller, battery bank and inverters. Hence, these major pieces of equipment work all together to light up your house efficiently. Interestingly, the PV panel generates Direct Current, and the inverter converts it into AC.

Alternatively, the alternating current feed the commercial electrical grid network. Likewise, the solar inverter contains huge capacitors to store the excess power and enhance the output waveform. To understand the intricate mechanism of inverters you should be aware of the three distinct types of solar inverters:

Standalone inverter

Standalone inverters work through an isolated system. It draws up the energy from the battery installed in the system. The photovoltaic arrays help to charge the battery. However, unlike grid-tie, the system is not interfaced with the utility grid.

Grid-tie inverter

Grid-tie inverter is consists of a special circuit to match the voltage and frequency of the grid. As it is connected to the utility grid, it supplies power to the grid. Moreover, the phase matches the utility supply. It can detect the presence of a grid. Hence, it gets connected to the utility grid when it can sense the presence of the grid.

Battery backup inverter

As the name suggests, it gets energy from the battery. Hence, it is interfaced with an onboard charging system to control the battery charge. Moreover, this inverter system is capable of exporting the excess energy back to the grid. In case of any power outrage, it supplies AC for selective loads. This inverter is known as a hybrid inverter.

Apart from these classifications, there are three other varieties based on their energy generation output:

Sine wave: local utility generator produces sine wave output. There is an in-built rotating AC machinery that triggers the production of the sine wave output. Most of these inverters used as domestic utility supply are sine waves. Moreover, sine wave power is expensive than the other two.

For example, Motors and microwave ovens produce energy to run the motor when connected to sine wave power.

Modified sine wave: It is almost like a square wave; however, it generates a low-efficiency current. A modified sine wave has a flat top, which might cause an occasional trigger into the waveform.  Moreover, it is rougher than pure sine thus, generates a distinct sound while running the motor.

For example, Lights, tools, TVs, computers can work with this interface system.  

Square wave: the waveform is generated in a square form. A square wave inverter is also known as a digital inverter. It generates AC output; however, it is not enough to run any large appliances. Moreover, it generates a humming sound, which also restricts its usability.

As you know, most of the electrical appliances we use at our home run on Alternative Current. Hence, sine wave inverters are the best choice when it comes to operating home appliances. However, it is important to note that one needs to maintain a solar inverter properly; otherwise, it would drain a colossal amount of electricity.

How to choose the right solar inverter for your home?

To choose the right inverter, you should have basic knowledge regarding the terms. If you are not aware of them, get some idea from the following lists:

Safety certification: Safety certification is a ‘MUST’ to have. It shows the inverter is certified by a testing laboratory.

Watts: It determines the power used by the device. If you have a 120 watts device, it means the device needs 20 amps at 12 hours. Hence, it shows the product of amps and volts.

Watt-hours: people often get confused about the watt-hours and watts. It shows how many watts and how many hours a device consumes. If a 100-watt bulb runs for 8 hours, it means it consumes 900 watt-hours.

AMPs: this metric shows the measure of electrical current at the very moment. It uses the number 1 coulomb per second.

AMP-hours: Amp-hour is the primary measure of the battery capacity. Most of the inverter users use the battery.

Efficiency: efficiency denotes the ratio of input and output power. Generally, an inverter cannot achieve 100% efficiency. Moreover, the efficiency of the inverter completely depends on the load. Hence, an inverter has an efficiency graph.

Internal protection: the crucial components of the solar inverter must protect the system from overload. In case of any lighting surge and power-related complications, the internal protection system should have an automated infrastructure to save the entire cycle.

Thus, an automated sensor is integrated into the system that commands to shut down the operations. In fact, for lower supply voltage, the system also protects the internal aspects. This helps to mitigate the risk of damage.

How to size an inverter?

Just like the size of the sine wave has a lot to do with selecting the right inverter. Similarly, you need to understand how to size an inverter?. However, before understanding sizing, another important aspect is to learn how inverters are rated:

How are inverters rated?

Continuous watts: The rating of the inverter entirely depends on the watt capacity. Continuous watt is the entire amount of watts an inverter generally supports. A 2000 watt inverter can power up to 2000 watts. Hence, to run the entire system accurately, you need an equal solar system and inverter watt.

If you want to run a couple of electronic devices simultaneously, you should ensure your inverter has the required capacity.

Surge Watts: the second factor that determines the rating is the surge watts. This shows the amount of power that can be supported for a few moments. So, it is the momentary watts. Thus, if a 2000 watt inverter is rated at 4000 surge watts, it means it can handle upto 4000 watts momentarily.

Similarly, as per the previous metrics, the solar system should also have the highest capacity of 4000 watts. Otherwise, the devices would collapse internally, damaging the entire electrical circuit.  

How to calculate power requirements?

Before you buy an inverter, you better calculate the typical wattage rating. It will help you to opt for the suitable one for your home. To estimate the power requirements, you need to have a rough idea of the wattage.

Remember, unlike a generator, an inverter has its own limitations. Thus, you can’t run the entire home with all inverters. Moreover, if the power prerequisite exceeds more than 4000VA, an inverter can’t serve your requirements. Thus, the question is, to what extent an inverter can run your home appliances?

In fact, if you use all the appliances together, the battery won’t last more than a couple of years.  

  The wattage rating of typical home appliances

AppliancesRequired Power
Fan (Ceiling)50-75 watts
Fan (table)25-50watts
CFL18 watts
Computer80-150 Watts
Laptop20-75 Watts
LCD TV (32”)150 Watts
Refrigerator160-250 Watts
Tube Light40 Watts

Do you know the prerequisites of power requirement for stating and running power are different? During 18 watts, CFL can take around 25 watts of energy. Meanwhile, the power consumption shifts to 18 watts. On the other hand, appliances like refrigerators and washing machines can multiply the vitality compared to standard running power.

Hence, before choosing the right inverter, you should also keep an eye on the starting power.

Tips for choosing the right inverter

  • Sine wave inverter is always better. It offers better longevity and offers better efficiency.
  • Always choose the inverter with high capacity (you can also calculate the load).
  • Most importantly, the power consumption of the inverter should be low.
  • It should definitely consume low electricity from the grid.
  • The battery of the inverter should be great.

Now, it’s your take

To conclude, if you are aware of the above-discussed facts, I am certain you will land up with a wise choice. Try not to comprise with functionality over price because it’s a long-term investment. Finally, I would always recommend finding a quality brand that offers durability and high efficiency.

People also asked:  

How do I calculate what size inverter I need?

As per the general rule, the size of the inverter should be equal to the DC rating of your solar panel system. IF YOU INSTALL A 6Kw SYSTEM, THE PROPOSED INVERTER CAPACITY SHOULD BE AROUND 6000 W.

How big should my solar inverter be?

YOU NEED TO FIGURE THE SIZE OF THE FUSE AND DEVICE THE AC WATTS BY DC VOLTAGE. You might need a 375 amp fuse or bigger. In case you need 500 amp, it is better to go for a 5000 watt inverter.

Matt

I’m Matt, a computer and electronic embedded system developer. Currently, working as an electronic engineer. In my leisure time, I do love to blog about technology stuff. Specially, new advance high tech devices. Portable solar systems are one of topic that I love to investigate. They are becoming more powerful day by day which keep me alert.

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