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  • Melissa Deaver

Adding Solar Panels To An Existing System

The average homeowner's energy consumption can change over time due to various factors. Perhaps more energy efficient appliances have been installed, an EV charger was added or heat pumps. Any scenario wherein you may be adding more to your current load brings up a great question - can I increase the size of my array after initial installation? The short and simple answer is, yes! Absolutely.


When to Expand Your Array

Expanding your current array is always possible, but it may not always be practical. Whether the array is rooftop mount or ground mount, you will need to ensure you have the space to support the additional panels. This may require some reconfiguration of your existing system. If your original system is a string inverter set up, then the capacity of that inverter would need to be determined. There's a chance that the inverter would need to be upgraded or supplemented, which can be an expensive task. If you are interested in adding battery storage to your expansion as well, then a larger inverter may be necessary.


Impacts of Solar Panel Expansion

The number one goal in expansion is to increase your power production and therefore reduce your electricity bill. Beyond that, however, there are several factors that will be affected by expanding an existing array that may impact your decision on whether or not to make the move.


Inverter Upgrades

A microinverter system is much easier to expand, because upon adding more panels to your array, you would simply add the microinverter to each panel. If you are upgrading a string inverter, the capacity would need to be assessed. If it cannot handle adding the additional panels to the current system, an upgrade would be necessary.


Net Metering

Upon expanding an array, the utility company must be notified in order to update the interconnection agreement. There have been several changes in the past years to the net metering programs, so it's important to look into these within your state and determine how this may affect you. Some states have decreased the amount they compensate customers for solar production. Older systems are grandfathered into these rates, but if you were to upgrade your system, you may be at risk of losing your initial rate.


Solar Incentives

Expanding a system usually means that you are excluded from many of the benefits offered when you first installed your array. You cannot, for example, claim another federal tax credit for the expansion if you have already claimed it for the original array.


Battery Storage

If you are considering expanding your current system, it may also be a good time to consider adding battery storage. Depending on the battery, a new inverter may be required.


When is Solar Panel Expansion a Bad Idea?

Expansion may not be a good idea if you are already matching your energy production with your solar array. Most utilities will only offer net metering up to a certain point (i.e. MidAmerican Energy offers up to 125% of usage). After that point, any extra power produced will go back into the grid without compensation to you.


Alternatives to Solar Panel Expansion

If expanding the number of panels isn't an option for you, there are other alternatives to increase production.


Reduce Shading

Check around your current array to see if there is opportunity to expose the panels to more sunlight. Sometimes cutting a few branches off a tree can increase energy production.


Add Power Optimizers

If the PV system has a string inverter and no power optimizers, then these can be added on afterward to increase production.


Replace Existing Panels

The efficiency of panels has increased dramatically over the last several years. It may be worth looking into higher wattage panels. If you had installed a 250 watt panel, for example, trading these out for a 450 watt panel would certainly boost your production.



Expanding an existing system can be expensive, but for some homeowners will be worth the investment. Take the time to sit down with a trusted installer and go over your options before making a decision.



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