Case Study: Can You Add Battery Storage to an Existing Solar System in Delaware County
If you already have solar panels and have been asking yourself, can you add battery storage to an existing solar system, the short answer is yes. This is exactly what Scott S. in Aston, Delaware County, PA did with his TerraSol system.
Can You Add Battery Storage to an Existing Solar System?
Yes. Most solar systems can accommodate a retrofit battery. But how it gets done depends on one thing above all else: your existing solar inverter.
Your solar inverter is the component that converts DC electricity (what your solar panels produce) into AC power (what your home uses). The type of existing inverter you have determines which battery options are available, what the project will cost, and whether any additional equipment is needed.
In 2014, TerraSol installed a 10.5kW solar energy system for Scott S in Aston, PA. The system was comprised of 48 PV panels at 235W each, equipped with M215 Enphase microinverters. Scott’s project spanned multiple roofs, and microinverters allowed us to maximize power production.
Fast forward to 2022. A forward-thinking Scott wanted to add energy storage to his existing system. He contacted TerraSol again to assist him in meeting his goal.
This opportunity, while exciting, presented a challenge: how could we best utilize Scott’s current investment, which still has plenty of life left, and adapt it to one of today’s many cutting-edge energy storage options?
Carl Santoleri, a battery system designer at TerraSol, came up with a clever solution. He found that we could reprogram the Enphase inverters and install the Enphase Encharge battery system, allowing for seamless energy storage implementation for Scott.
TerraSol installed 2 Encharge 10 Batteries and the Enphase Grid interface panel. Now, Scott has 20kWh of power to back up his critical loads.
The system works seamlessly, sensing utility power outages and automatically switching to battery mode when they occur. Once the power comes back on, the system returns to normal, and the homeowner never sees a blip.
The ability to utilize the existing microinverters, eliminating the need to replace any existing equipment, made the project very affordable and fast, and Scott no longer has to worry about power outages.
Read the article: 3 Things You MUST Know About Solar Power & Small Businesses
Scott's Project: A Real Delaware County Battery Retrofit
Scott's existing system used Enphase M215 microinverters — not string inverters. This made the battery retrofit path direct.
Carl Santoleri, a battery system designer at TerraSol, found that the Enphase microinverters could be reprogrammed to work with the Enphase Encharge battery system. This eliminated the need to replace any existing equipment. Both the solar panels and the existing solar inverters stayed in place.
TerraSol installed two Encharge 10 batteries and the Enphase Grid Interface Panel. Scott now has 20kWh of stored energy available to back up his critical loads.
The system works automatically. When a power outage happens, it detects the loss of utility power and switches to battery mode. When grid power comes back, the system returns to normal. The homeowner never sees a disruption.
Because we worked within Scott's existing solar system — reusing the microinverters and simply adding the battery setup — the project was faster and more affordable than a full system swap. This is what a well-matched AC-coupled system retrofit looks like.
The key was that Scott's existing inverter technology was already part of a battery-ready ecosystem. Not every existing solar setup will have that same advantage, which is why a site assessment matters.
What Battery Options Work With Existing Solar Systems?
The right battery setup depends on your inverter type, how much storage capacity you need, and your budget. Here are the most common options for battery retrofits in Pennsylvania:
Enphase Encharge — Works natively with Enphase microinverter systems. AC coupled. Scalable, so you can start with one battery and add more later. Uses lithium iron phosphate chemistry, which has a longer cycle life and no active thermal management requirements.
Tesla Powerwall — A widely used home battery. AC coupled out of the box. Works with most existing solar setups regardless of inverter type. A practical choice if your system uses string inverters and you want to avoid a full inverter replacement.
SunPower SunVault — Designed for SunPower solar panel systems. If you had SunPower panels installed, this is the matched battery system.
Sol-Ark with Lithium Iron Phosphate Batteries — A better fit for homes wanting a DC coupled system or going fully off-grid. TerraSol has completed full off-grid projects with 163kWh of lithium iron phosphate battery storage and Sol-Ark inverters.
If you want a whole-home backup rather than just a critical load backup, a larger battery or multiple batteries will be required. A single 10–13 kWh battery handles critical loads: refrigerator, lights, outlets, and medical equipment.
Running a full home through an extended outage — including heat pumps, EV charging, and major appliances — requires significantly more storage capacity.
You can also check out our case study on the New Castle County home solar installation, where they didn't have to sacrifice the aesthetic or curb appeal of their home to have their solar system installed.
What Does Adding Battery Storage Cost in Delaware County, PA?
Installing a battery storage system costs about $15,228 on average nationally. Costs for a 10–13 kWh battery range from $6,000 to $23,000, depending on the battery brand, the installation complexity, and whether electrical panel work is required.
For Delaware County specifically, a 13 kWh battery system typically costs $16,575–$22,425 before incentives.
The 30% Federal Investment Tax Credit (ITC) applies to battery retrofits. If the battery is charged primarily by solar, you can claim the 30% credit on the cost of the battery installation. This can bring a $19,500 install down to around $13,650 out of pocket. Learn how to take advantage of the solar energy tax credit.
Additional cost factors for Delaware County homeowners:
Inverter compatibility: If your current inverter needs to be replaced to support battery storage, add $1,500–$3,000+ to the project. In Scott's case, no inverter replacement was needed.
Electrical panel upgrades: Some homes need panel work before a battery can be added. Your installer will identify this during the site evaluation.
Battery size: A smaller battery covers critical loads. Multiple batteries are needed for whole-home backup.
Battery prices have dropped considerably. In 2020, only 6% of residential solar systems included battery storage. By 2024, 25% of new solar installations included batteries. Lower battery prices and more frequent grid outages are both pushing that number higher.
If you are also interested in how we handle solar installation permits, you can check our case study on PA solar installation permits to learn how our TerraSol team handled it flawlessly.
Does Adding Battery Storage Affect Net Metering in Pennsylvania?
Net metering in Pennsylvania lets your solar panels send excess power to the grid in exchange for bill credits. Adding a battery does not eliminate net metering — it changes how you prioritize excess power.
With a battery, your system charges the battery first with excess solar energy. Once the battery is full, additional excess power flows to the grid under net metering as it normally would. You get the benefit of stored energy for nighttime use and outage backup, plus credits for anything your battery cannot hold.
Some homeowners also use battery storage to reduce electricity costs by drawing from stored energy during peak rate hours instead of pulling from the grid. As utility rates continue to rise, this kind of load shifting becomes more financially meaningful.
How Much Battery Storage Do You Need?
Battery size comes down to what you want to back up and for how long.
Critical loads only: A single 10–13 kWh battery covers a refrigerator, lights, phone charging, internet, and a few outlets through an overnight outage. Scott's setup — two Encharge 10 units for 20kWh total — gave him solid coverage for critical loads through multi-day outages.
Whole-home backup: Add in HVAC, electric water heating, heat pumps, or an EV charger, and you need significantly more storage. Plan for multiple batteries.
Extended outage coverage: Multi-day grid independence requires a full load analysis. You will need to know your average daily energy use, your solar production rate, and how many days of backup you want to be able to cover.
A qualified installer will review your actual solar production data, your home's energy usage, and your backup goals before recommending a battery size. Do not size a battery based on guesswork.
If you are interested in energy storage coupled with your existing PV system, please reach out to the TerraSol team today.
Is Your Existing System Ready for a Battery Retrofit?
Most existing solar PV systems installed in the past decade can support a battery addition. Here is what determines compatibility:
Inverter type:
Enphase microinverter systems: strong retrofit candidate, especially with Encharge batteries
String inverters under 10 years old: AC coupling with a standalone battery inverter (Powerwall, etc.) is usually the path
String inverters 10–15 years old: evaluate a hybrid inverter upgrade alongside the battery addition
Hybrid inverters already installed: easiest path to a DC coupled battery system
Electrical panel: If your panel is undersized or dated, battery installation may require panel work first. Not always the case, but it needs to be confirmed.
Roof and mounting: Your solar panels installed on the roof do not need to be touched. The battery system installs separately — in a garage, utility room, or on an exterior wall.
Permit and interconnection: Adding battery storage to an existing solar system requires a permit and an updated interconnection agreement with PECO. TerraSol manages all permit applications and utility coordination. Review the basics of how photovoltaic systems work before your consultation if you want to come in informed.
Why Delaware County Homeowners Are Adding Battery Storage Now
Power outages in southeastern Pennsylvania have increased. Between summer peak demand, winter storms, and aging grid infrastructure, grid reliability is a real concern.
More solar homeowners are choosing to add battery backup to their existing systems — not just as a precaution, but as a way to gain greater energy independence.
Beyond outage protection, battery storage helps reduce electricity costs by letting you draw from stored energy instead of grid power during peak hours. And with the 30% federal tax credit still in place, the after-incentive cost of adding a battery has come down meaningfully from where it was five years ago.
The industry data reflects this. In 2020, only 6% of home solar systems included battery storage. By 2024, that share reached 25% of new residential solar installations. For homeowners who already have solar panels installed, the question is no longer whether to add storage — it is when, and how to do it correctly.
See what a full residential solar installation looks like in Delaware County.
Get Started with a Battery Retrofit in Delaware County
If you already have solar panels in Delaware County or anywhere in southeastern Pennsylvania, TerraSol can evaluate your current system for a battery retrofit at no cost. We have been installing and servicing solar and battery systems in this region since 2009, and Scott's project in Aston is one example of how we approach adding storage to existing systems.
If you are asking yourself, " Can you add battery storage to an existing solar system, reach out to the TerraSol team today to find out exactly what your system qualifies for.
