Can Solar Inverters Work without Batteries?

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Solar inverters have really taken off in popularity in recent years as has renewable energy. Basically it is a device that converts solar power into AC so appliances and electronics can use it. But do you need batteries to run an inverter?

If your solar panels are connected to a power grid, the inverter can run without batteries. If you are off the grid, batteries are needed to store solar power.

Types of Solar Inverters

While solar inverters can function without batteries, there are situations when you might need it. To get a better idea, we have to consider the different types of solar inverters available.

Battery Inverter

You can use a battery inverter to store energy produced by solar panels. You can install these inverters whether you are on or off the grid.

For safety reasons, you cannot use solar panels in case of a grid failure. If the inverter and solar panels were active and generating electricity, it would endanger the people fixing the power lines.

Grid tied solar panels can reduce your power bill, but you can’t use it during a power failure. With a battery inverter, you can store solar energy and use that to power your home.

My pick: Ampinvt 6000W Pure Sine Wave Inverter

String Inverter

In this system, solar panels are joined together in a string and connected to a single, central inverter. Central or string inverters are the most widely used today due to the low cost and efficiency.

Once the string inverter is configured, it converts the energy produced by solar panels into AC. If you’re on a budget or new to solar, a string inverter is a good option.

Micro Inverter

Micro inverters have the same function as string inverters. The difference is that each solar panel has a micro inverter. In a string inverter setup, all the solar panels use one inverter.

In this system, a micro inverter is installed under each solar panel. If you have 30 solar panels, there are 30 micro inverters. However, newer inverters are now capable of supporting up to 4 solar panels.

Micro inverters are more expensive than string inverters, but it is more efficient. Because each solar panel has its own inverter, if one panel gets shaded, it won’t affect the rest.

With a string inverter, all the solar panels are connected to it. If debris cover one of the panels, energy production goes down for all the solar panels.

My pick: Renogy Pure Sine Wave Inverter 3000W

Hybrid Inverter

This is a microinverter that you can use on or off the grid. It comes with a battery charger, which allows you to store solar energy in batteries.

Hybrid inverters have a mechanism that can power appliances in case of a grid failure. This will only work however, if your solar system can be activated during a power outage.

My pick: PowerMr 3200W Hybrid Inverter

The bottom line is you have a lot of options. If you are still deciding, knowing the advantages and disadvantages of solar is essential.

Does My Solar Inverter Need a Battery?

Okay, so now we’re familiar with the various inverter types. But how do you know if your system needs a battery or not?

It depends on how your solar panels are configured. How much solar power you want to use is another factor.

First a quick recap of how inverters work with solar panel systems: solar panels produce direct current (DC). This current is stored in the battery. The inverter converts the DC current into AC, powering appliances.

Grid Tied Solar Panels

If your solar system is connected to a power grid, batteries are not required. It’s not necessary for solar panels to store power in a battery. The current goes directly into the inverter and is turned into AC.

It is possible to install batteries in a grid tied system. This is useful if you want backup power in case of emergency. While you cannot use solar panels in case of an outage, a filled battery bank can run appliances.

Off Grid Solar Panels

If your home isn’t connected a grid, batteries are a must. Otherwise you won’t have any power at night or when it rains, snows, the sky is overcast etc.

Solar panels can only produce power when the sun is out. In a grid tied system that’s not an issue. You can go solar at day and back to the grid at night.

If you are off the grid, you’ll need another source to keep the power on at night (or when it rains). With batteries, you can store solar energy and use it when the sun is not there.

How Long Can Solar Inverters Run?

If your solar panels are tied to the grid, an inverter will run as long as there is power. It can draw from the solar panels or from the grid, depending on your setup.

If your inverter is connected to a battery, you can calculate its runtime with a simple formula.

Usable battery capacity (ah) x voltage = watt hours

Watt hours / load watt requirements x inverter efficiency = inverter runtime

Inverter efficiency refers to how much energy is lost during conversion. Modern inverters are 90-97% efficient, the higher the rating the better.

Usable battery capacity or depth of discharge (DOD) varies. Lead acid batteries have a 50% DOD, AGM around 70% and lithium batteries from 85-98%.

Suppose you have a 3000W 12V inverter with a 95% efficiency rate and a 12V 100ah lithium battery with a 90% DOD. You are going to load it with appliances that use 750 watts. How long will the inverter and battery last?

A 100ah battery with a 90% DOD means 90ah is usable, so:

90ah x 12V = 1080 watts

1080 watts / 750 watts = 1.44

1.44 x 95% = 1.368

The runtime is 1.368 hours for a 750 watt load.

You can use this formula for any inverter regardless of its size or efficiency rating. You just replace the values with the appropriate one for your system.

What Inverter Size Do I Need?

It depends on how much electricity you use and how much of that is going to come from solar. Here are some guidelines to help you get started.

Calculate Power Consumption

You can find this in your monthly power bill. Next, decide how much of that is going to run on solar power.

Are you going to use solar panels all day and switch to the grid at night? Do you want to use solar power most of the time? Or do you plan to disconnect from the grid entirely?

How you answer these questions will determine how many solar panels, batteries and inverter you will need. Staying on the grid will allow you to install a smaller solar system, but you won’t be energy independent.

Inverter Efficiency and Capacity.

Once you’ve determined how many watts you’ll run on solar, you can buy the right number of solar panels. Add 10-15% to the total as solar systems are not 100% efficient.

Decide on inverter size and type. You want to have reserve power available, so choose an inverter that has a bit more capacity than your total power consumption.

Choose Inverter Type

As to the type, it depends on many factors. If you are on a budget, a string inverter is the best choice. It is affordable and provides good performance.

Make sure your solar panels are regularly maintained. If a single solar panel is obstructed, it’s going to affect the whole system.

If you want maximum performance, buy micro inverters. It is a good investment if you want to get the best results from your solar system.

Keep in mind that inverters only convert power produced by solar panels. The amount of current generated will depend on the solar panels, and how much you can use depends on the battery capacity.