Inverter Sizing Tips—And How to Tell You Got the Wrong Size

Inverter Sizing Tips—And How to Tell You Got the Wrong Size

When you hear solar installers talk about the “size” of your equipment, they’re usually not talking about physical proportions. Rather, they’re referring to just how much power the equipment can generate or store. To get the right size of system, you’ll need to carefully calculate your home’s energy needs. That calculation can then be used to ensure you purchase the right size for all of your different solar equipment, including solar batteries that store energy for your home. But how do you perform those calculations? And how can you tell if you’ve bought the wrong size of solar inverter? Keep reading to find out.

How to Calculate Your Power Needs

As stated above, in order to buy the right size of solar equipment, you need to calculate how much power your home uses. Every inverter has a power rating that’s listed in watts. This rating shows just how much wattage it can supply to your home. In order to know if that’s enough, you’ll need to look at the wattage requirements of all the appliances and other electronic equipment in your home. In modern homes that have a lot of electrical devices, this can be a hefty list. However, it’s important that you not overlook any power-using device in your home, or else your calculations will be inaccurate.

Here are the wattage requirements for some common household appliances that you likely have in your home:

  • Refrigerator – 400 to 800 watts
  • Game consoles – 50 to 100 watts
  • TV – 60 to 120 watts
  • Microwave – 600 to 1200 watts
  • Central AC – 1200 to 1500 watts

Of course, you’ll also need to consider a number of other items that you don’t necessarily use every day, like your dishwasher, washing machine and clothes dryer, sump pump if you ever need it, and more. Obviously, remembering every single power-using item in your home can be difficult, so it may be a good idea to ask a professional solar power installer for assistance.

Additional Tips for Calculating Power Usage

Even if you’re meticulous, many homeowners who try to perform their own calculations will end up with a system that’s too small for their home’s needs. Here are a few tips that may help you to avoid this problem:

  • Consider the type of solar panels you have. Certain types of panels are more efficient than others, and that will impact the amount of energy that flows into your inverter (more on the importance of this in a moment).
  • Think about your surge power needs. In addition to basic power consumption, many appliances have surge power requirements, a brief pulse of a higher amount of power to start the appliance. Examples that commonly use surge power include HVAC units, refrigerators, and clothes dryers. If you don’t account for these needs, you may end up without enough power to start these appliances.
  • Increase your calculation by at least 10%. Once you’ve totaled up your wattage needs, add another 10% to 20%. This will help ensure that you have enough power for your home at all times, even when your power consumption spikes.

These extra tips can make all the difference when it comes to picking the right size of inverter.

How Do You Know If You Got the Wrong Size?

So, what will happen if you do all these calculations incorrectly, or if your power needs increase and your system no longer supports those needs? How will you know there’s a size issue with your inverter? The answer will depend on whether it’s just your inverter that’s inappropriately sized or your entire system. If your entire system is undersized, you will find yourself frequently experiencing brief power outages. Perhaps it happens when you try to use something with surge power, or maybe it’s just in the evenings, when your entire family is home and you’re using more electricity. But if the lights are constantly flickering or you’re struggling to get enough power to the appliances, you know your system is the wrong size.

However, if it’s only your inverter that’s undersized, then the wattage rating on the inverter won’t match the wattage output of your solar array. This means that your panels will be pumping more power into your inverter than it’s actually capable of handling. This typically leads to the inverter overheating, which can damage its components and lead to early breakdown of the components. This is why it’s incredibly important that you apply your wattage calculations to all the equipment in your system.

Typically, this mismatched sizing issue will occur when homeowners want to upsize their system by adding more panels, but they don’t upsize their inverter as well. This is why it’s important to look for new SMA inverters with an appropriate wattage rating if you ever decide to add more solar panels to your home.