Sizing Your Inverter for Your Solar Power System: The Basics
Today, we're continuing the educational theme and diving into the final step of properly sizing an entire solar power system: sizing your power inverter.
If you've been following this series of lessons, you're already on the right track to understanding solar power. If not, we recommend checking out our previous lessons where we discussed basic solar terminology, sizing your battery bank, and building your solar panel array. Trust us, they’re not as boring as they sound.
If you have been following along and you’re ready to expand your knowledge, let’s get started and dive right into understanding inverters!
Why Is Sizing Your Inverter Important?
Think of your inverter as being like the heart of your solar power system. It converts the DC (Direct Current) electricity generated by your solar panels into the AC (Alternating Current) electricity that your home appliances and portable devices can actually use. Without an appropriate power inverter, you’re basically just stuck with a battery bank that isn’t much better than a few car batteries.
On top of that, choosing the correct size of power inverter is crucial for the overall efficiency and power output of your entire solar power system. Yep, it’s that important!
Step-by-Step Guide to Sizing Your Inverter
While it may sound complicated, sizing an inverter doesn’t need to be some mysterious process. You may need to review our previous lessons, but once you have, just follow these four simple steps:
Step 1: Determine Your Total Power Consumption (Wattage):
You’ll need to start by identifying how much power you need to run all of your appliances and devices at once. For example, let's say your total power consumption is 1,700 watts. This is the crucial number you'll need to use in order to properly size your inverter.
We already discussed how this can be calculated in our battery sizing lesson. If you need a quick refresher, check out our Sizing Battery Capacity video.
If you don’t take the time to do this step correctly, there’s a good chance your system won’t be capable of running everything at the same time, which can be frustrating and limiting in real-world situations.
Step 2: Check Your Solar Panel Array Size (in Watts):
Next, look at the size of your solar panel array. This is the total wattage of all of your solar panels, which you also should have determined if you followed along with our previous lessons.
Let’s say your combined solar array is 2,500 watts, you'll want an inverter that can handle at least this level of input power. If you do not have an inverter that can handle this, some of the power your solar panels generate will be wasted.
Step 3: Determine Your Voltage Requirements (120V vs. 240V):
Determine whether your system will be running at 120 volts or 240 volts. Most of your basic home appliances run on 120V, but some of the more demanding appliances and power tools may require 240V power. Just check ahead of time and save yourself the headache.
Step 4: Choose the Right Size Inverter:
Now, let's find an inverter that meets your needs.
In the example we used above, we determined that we need to supply 1,700 watts of power at the same time. In this type of situation, we would recommend selecting an inverter that offers a bit more capacity than your exact needs, such as a 3,000-watt inverter. This gives you room to expand your system in the future and it ensures that you won't max out your system if you decide to add more appliances at a later point.
For input, you'll need to match or exceed your solar panel array size. Again, let’s say you have a 2,500 watt solar array, look for an inverter that can handle at least this amount of input. As always, it's always good to have extra capacity for future expansion.
Example Inverter Selection
We found a great inverter on the EG4 website that has an output of 3,000 watts and has a solar input capacity of 5,000 watts. This is perfect because it not only meets the current needs of our example scenario, it would also enable future expansion.
On top of that, we actually found the same inverter on Signature Solar’s website for under $700, making it even cheaper than shopping through EG4 directly!
Remember, it’s almost always more cost effective to just buy a bigger component than you need in the beginning than it is to replace it in the future.
Extra Considerations for Choosing Your Inverter Voltage
As we mentioned, most inverters are designed to handle either 120V or 240V. If you're only running 120V appliances, a single 120V inverter will suffice. However, if you plan to run 240V appliances, you might need to pair two inverters together, or opt for a hybrid inverter that can handle both voltages.
Grid-Tied vs. Off-Grid Systems
If your goal is to sell excess solar power back to the grid, keep in mind that many places are phasing out or reducing incentives for this.
For example, California's NM 3.0 Program has significantly reduced the payments for solar power fed back into the grid. Given this trend, we’d recommend considering an off-grid or hybrid system instead of going with a grid-tied inverter.
Our Final Words
Sizing your inverter might seem like a daunting task, especially when you’re scrolling through online retail shops and finding hundreds of different options, but with the right information, it's actually pretty straightforward.
Remember to calculate your total power needs, check your solar panel array size, and choose an inverter that offers a bit more capacity than you need right now. You’re already doing yourself a huge favor just by reading up on this stuff before you buy, so give yourself a pat on the back.
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