Solar Panels

Adding Solar Panels to an Existing System: Is it worth it?

By:Michael Johns

You’re not alone if your electricity usage continues to grow every year.

The modern world continues to add a growing number of electrical devices into our homes.

As we shift away from the reliance on fossil fuels, this will only continue.

You may have already decreased your energy bills by installing a solar panel system but now it might be time to add more capacity.

Perhaps you’ve switched to an electric car or your family is growing.

Whatever the reason, it’s a good idea to look at the options to help cope with the increased electricity demands.

Unfortunately, adding in new solar panels isn’t as simple as the first installation and there’s several factors to consider.

Let’s go through all the factors before you start making any decisions.

P.S. You can also read How to Add a Portable Solar Panel to an Existing System

Can You Add Solar Panels to an Existing System?

A house with new solar panels added to old system
A house with new solar panels added to old system

Yes, adding solar panels to an existing system is possible. It is very common to increase the solar capacity of your home.

Of course, you’ll need to figure out the best way to complete the job, so it’s always best to work with a professional to get the correct solution.

It is worth noting that it can be hard to find installers willing to work on the job if it is only a small amount of solar panels. Usually, companies have a minimum number of panels they will install to make it financially viable. You should try to contact the original installer first as they will be the most likely candidate to easily do the work.

Adding to this, you’ll need to think about how much more energy you need, available space, compatibility, and other components. But don’t worry, we’ll look at these points next.

Energy Needs

The most important factor is how much additional electricity you need to generate. This will directly relate to how many additional solar panels you will need. 

To do this you can start by looking at your energy bills. You can analyze your statement to see how much electricity you’re drawing from the main grid and the production from your solar panels. You can even use Net Energy Metering to see how much credit your solar panels generate (or not).

You should quickly be able to see how much extra power you are using from the main grid. With this information, you can then start to work out how much extra solar power you need.

This should give you a good idea and you should pass on your bills to the installer so they can make detailed estimates. They will be able to take into account your location and amount of sunlight for added accuracy.  

When working energy needs out, you should be careful not to oversize your system. This will lead to excess expense and energy companies won’t pay you for generating too much electricity! All you will end up with is too much credit which eventually expires…

Available Space

Have you thought about whether you have enough space for additional solar panels?

A roof with no space on it for more solar panels
A roof with little extra space for solar panels

You might be thinking that only half your roof is covered, so it is just a case of installing more on the other side. The problem here is that solar panels need to be mounted in a specific direction and angle for greatest efficiency. 

If you look at your current setup you will notice that it points towards the sun. If you try to install panels on the opposite angle of your roof they won’t generate anywhere near as much power. A shaded solar panel can be 70% less efficient!

Running out of useful roof space means you’ll need to find another solution. Think about other sunny areas of your property such as garages, carports, sheds, and flat ground. (Solar panels can be mounted on the ground too).

Solar panels on garage
Find extra space on garage roofs


A big stumbling block can be compatibility. You can’t just slap any solar panels into an existing system. This is why it is best to use your original installer. They will be confident with working on the equipment and be able to supply the same type of solar panel you already have.

But what if those solar panels aren’t available anymore? Afterall, the originals could be decades old. Well, you want to match them as closely as possible with the same power and cell structure. Many installers won’t even do a job as they can’t source the same solar panels, plus they don’t want to interfere with existing systems and warranties.

Inverter Size

It’s obvious to say but extra solar panels mean generating extra power. You must ensure that the other components in your setup can handle the boot.

This is particularly important with the inverter. A power inverter is designed to deliver a certain maximum wattage as it converts the DC to AC electricity. It is likely you will need to upgrade your inverter to cope with the added power your home is drawing via the solar panels.

If your solar panels use microinverters then this won’t be a problem. A microinverter is connected to each individual panel to make the electrical conversion. You can simply add more solar panels with microinverters.

How to Add Solar Panels to an Existing System

There’s a couple of things you will need to do to get your extra solar panels installed. This includes finding an installer, permits, and interconnections.

Finding an Installer

Without doubt the biggest challenge to adding more solar panels is finding a company willing to do the job. If the work is too small or complicated many installers will simply say no. You might find that everyone you call will reject the work as they don’t work on systems they don’t sell.

Reasons installers say no:

  • Job too small
  • Don’t work on systems they don’t sell
  • Warranty issues on existing system
  • Don’t have compatible solar panels

It is always best to speak to the original installation company to complete the work. If you are still struggling to find someone, ask the manufacturer for a list of companies that stock your solar panels in the area.

Permitting and Interconnecting

As your electricity production interacts with the main grid, you will need to contact your energy supplier. It will require you to submit interconnection documents which includes key information including number of solar panels, inverter details, and local permits. You will likely have to submit a new application and have a reinspection if you introduce a significant amount of extra power.  Any good installer should help you through this process.

Consider Adding Batteries

While you’re thinking about making adjustments to your solar panels, consider incorporating solar batteries. 

Solar batteries allow you to store electricity generated by your solar panels. This gives you the comfort of a power backup when there is a power outage.

Batteries can also help save you money when you are on a Time-of-Use (ToU) tariff. Energy suppliers often have higher prices when electricity demands are higher, for example in the evening (also when solar panels stop working). At these expensive peak times, you can draw energy from your batteries. This allows you to offset against the main grid and reduce bills.

Pros and Cons of Adding Solar Panels

At first it might seem like it can only be beneficial to have more solar panels. 

Of course, you will be able to generate an increased amount of electricity but there’s a number of other pros and cons to weigh up. Let’s go through them.

Advantages of Adding Extra Solar Panels

  • Increased electricity
  • Cheaper energy bills
  • Environmentally friendly
  • Added self reliance
  • Extra power for things like electric vehicles 

Disadvantages of Installing Extra Solar Panels

  • Hard to find installers
  • Expensive upfront cost
  • Oversized solar systems can be wasteful (Energy companies won’t pay you money, they will issue credit which eventually expires.)

Final Words on Adding Solar Panels to an Existing System

As you can see there’s a lot to consider when adding solar panels to an existing system.

It is always useful to speak to the original installer as they’ll have an easier time making the adjustments.

If you’re looking to add extra solar power to reduce bills and support more electricity usage then it’s definitely worth looking into.

Just take the time to think about if you have enough sunny space for the extra equipment. 

And be aware, that an oversized solar panel system that always generates more electricity than you can use will cost you in the long run! Building up credit with your energy company is only useful if you use enough electricity to spend it.