Sizing the inverter: What size inverter do I need?

Solar panels are used to convert the sun’s energy into electricity, which can be used to power any electrical appliance. However, to make the electricity usable for many of these appliances, you need an inverter.

While inverters are a necessary piece of equipment for solar set-ups, they come in a range of sizes (or capacities), and choosing the right one can be a little tricky. In fact, one of the most common questions we hear from customers is: “What size inverter do I need?”

This article aims to help you answer this question. Read on to learn more about what inverters do and how to go about sizing an inverter for a solar system.

Do I need an inverter?

If you have a solar system, then yes, you do need an inverter. Inverters are a vital part of any solar energy set-up as they convert the direct current (DC) generated by the panels into alternating current (AC).

Without an inverter installed in your solar system, you would only have access to DC electricity coming directly from your panels. AC is the form of energy used by the grid and what powers most household appliances, so the inverter makes your solar energy usable.

What can I run with a solar inverter?

The majority of household appliances and a lot of commercial equipment run on AC electricity. There are several reasons for this. For example, DC electricity loses more energy in the form of heat, so it is more expensive and difficult to transport. It is also related to safety, with DC electricity carrying a greater risk of fire.

Some common examples of appliances that run on AC power include:

• Air conditioners

• Power tools such as drills, grinders, sanders, and saws

• Refrigerators

• Televisions

• Computers

• Electric lights

• Microwaves

• Blenders and other kitchen appliances

• Washing machines and dryers

• Dishwashers

One big exception to this is any device or appliance that is powered using a battery. Battery-powered items rely on DC for charging, meaning mobile phones, laptops, and electric cars all require a DC input.

How do I choose the size of the inverter?

Inverters for solar range in size, so it can be difficult to know which is the right fit for your solar set-up. Thankfully, it’s not quite as complex as it may seem at first. Solar inverters are rated in watts (W), as are solar panels themselves, making it relatively simple to match the correctly sized inverter to your system. However, there are a variety of other factors you should take into account when choosing your inverter size.

The rating of your photovoltaic (PV) array

The main thing you’ll need to consider when choosing the size of your solar inverter is the size of your solar array. The purpose of an inverter is to convert the DC electricity produced by your solar panels into AC so it can power a range of common appliances. This means the inverter has to be able to deal with the quantity of energy it’s receiving from the panels.

As a basic estimate, you should try to roughly match the size of the inverter to the size of the solar array. Solar arrays are generally rated in kilowatts (kW), so you can easily match the ratings. For example, you may have a 3 kW solar array installed on your roof, so the ideal inverter size is likely to be around 3 kW as well (or 3,000 W). The ratings don’t necessarily need to match exactly, but it should give you a good general idea.

Helpfully, manufacturers will usually provide a comparison table with recommended array capacities that can be matched with a specific inverter. It’s important to pay attention to these recommendations as failing to follow them could have implications for your warranty.

The size of your building

The size of your building is important when sizing an inverter for a solar system. This is because the capacity of your solar array is directly linked to the number of panels you can fit in your array, and solar panels are usually mounted on a building’s roof. Therefore, building size is a key factor in array capacity and, consequently, inverter size.

Learn about our Mini Inverter products.