Grid-tie systemsPV system design

Hunger for power: How to add solar panels to your system

Have you bought an electric vehicle? Or switched over from gas to electric heating? Or maybe just noticed that your solar system is no longer enough to power your house? Whatever the reason, you’ve faced the need to expand your solar system and add more solar panels. Let’s break down how to do it the right way. 

Do you really need to add more solar panels?

If you need more power, expanding your solar panel system is logical. But if your energy consumption pattern hasn’t changed but your system is no longer satisfying your needs, don’t rush to buy new panels. First, do a checkup.

How long has it been since you’ve cleaned your solar panels? Dust and dirt can decrease energy generation by up to 25%. Is everything all right with the wiring and the panels themselves? Perhaps squirrels chewed up some wires or a storm damaged some of the modules that knocked down the performance of the entire solar system. 

Before adding more solar panels, make sure that your existing solar system is running as it should. If you’re making the most out of it, but are still running out of power, here are three options you have.

Option 1: Rebuild your system from the ground up

If your system is an old one, has been experiencing frequent issues and has long outlasted its useful life, you can take it all down and build a new system from scratch. Modern solar panels are more space efficient than they used to be and age slower. Besides, they are cheaper — a solar system now costs 80% less than it used to 10 years ago. Read our article on best residential solar panels to get a better insight into the latest advancements.

Option 2: Add a separate system

If you’re not ready to part with your existing system, but are also not sure about upgrading it without messing it up, you can install a separate system. This system will not be connected to the existing system, so you don’t need to match anything. You can choose panels with any power output and either connect them to a separate string inverter or each panel to its own microinverter.

Option 3: Expand the existing solar system

Adding more solar panels may seem like the easiest option, but don’t jump to conclusions. The complexity and cost of this endeavor depends on what you decide to do with an inverter. 

Same inverter and extra panels

You can choose to keep the old inverter and add more panels to the string. Even if you have a 5kW system and your inverter is rated for 5000W, there is room to expand. The trick is that the actual power output of your panels is less than their rated power output stated in the spec sheet. That’s why your inverter can handle a 33% more powerful panel system. Adding too many extra panels though will result in clipping where an inverter gives out much less usable power that it receives from the array.

When you add panels to the same string, they have to be identical in voltage and power output and be installed in the same place. The specific feature of the single MPPT-input string inverter is that it keeps the power of the entire solar panel chain down to its weakest link. However, if your inverter has multiple MPPT-inputs, you can add a separate string that doesn’t have to be matching.

New inverter

If you are not sure if your old inverter can satisfy your growing demands, you may replace it with a new and more powerful one. And here you have two options.

You can either buy a more powerful but single MPPT-input inverter and then either buy exactly the same panels or find the ones that are similar in wattage, voltage and amperage, and install them in the same place as your old ones. Or you can buy a multiple-MPPT-input inverter and connect your old panel string to one input and your new panel string to the other input. In this case, you don’t need to match anything.

Microinverters

This is the easiest option for expanding. If you have microinverters, you don’t need to bother about anything at all. Just buy new panels, new microinverters, and pick a sunny spot for them.

Things to consider when adding solar panels

When expanding your solar system, you not only need to calculate the number of panels and inverter capacity required but also consider some other factors that may influence your decision to go with one way or another

Available roof space

The primary constraint when adding more solar panels may be the lack of space. Determine if you have enough unshaded roof space to accommodate the desired number of panels. It’s essential to ensure that your new panels will receive adequate sunlight throughout the day for optimal energy generation.

Estimate the load-bearing capacity of your roof. A single solar panel weighs between 40 and 60 pounds, plus additional mounting hardware. If you’re living in an old house, even this weight may be considerable.

40-60 lb

weight of a solar panel

Permissions and net metering

Will expanding your solar panel system require obtaining additional permits or submitting additional interconnection documents to your utility provider? This can depend on how many panels you’re adding, whether a new inverter is needed, as well as your local permitting requirements. Check with your utility provider to understand all the regulations and rules to avoid any legal issues.

If you have a net-metering option, calculate what’s more cost-effective: to draw electricity from the grid or buy new panels. If you opt to increase your system’s capacity, make sure it stays within the limits permitted by your net-metering policy, otherwise you may have problems with your energy provider.

Panel compatibility

If you are expanding your system by adding new panels to your old ones and mixing them within the same string, you need to make sure they have the same wattage, voltages, and amperage. If you have an old system, you may have trouble finding similar PV modules.

Let us do the math

 A1SolarStore Calculator helps you figure out the right size of a solar system for your home, choose the panels, and evaluate your savings from solar over the years.

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Years of experience in translation and a love of nature help Julia find the right words to encourage going solar. She joined the team in 2023 and is happy to make her contribution to a greener future.

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