Battery retrofit

Already have solar? Add a battery.

Most national installers refuse to retrofit batteries onto systems they did not build. We do hundreds every year across CT, MA, and RI — AC-coupled, DC-coupled, original installer doesn't matter.

Get a free quote 203-903-4091

By the numbers

  • Existing systems Any brand · age
  • On-site time 1 – 2 days
  • Project timeline 3 – 6 weeks
  • Federal ITC 30% on battery
Why retrofit with us

Four reasons we'll touch the work other installers won't.

Battery retrofit is its own discipline. We built a team around it because solar systems do not stop existing the day their original installer goes out of business.

We take the systems we did not install

Most national installers refuse to touch a system they did not build. Teamsun retrofits hundreds of systems every year — original installer does not matter.

Both AC and DC coupling

AC-coupled retrofits (FranklinWH, Enphase) work with most existing inverters. DC-coupled (Tesla Powerwall 3) requires more careful integration. We handle both paths.

Program enrollment included

CT ESS and MA Connected Solutions both accept retrofitted batteries. Teamsun files the enrollment paperwork as part of every retrofit project.

30% federal ITC on the new battery

Per the Inflation Reduction Act, the battery portion qualifies for the federal ITC even when retrofitted onto an older solar system. We file the paperwork.

Compatibility

What plays nicely with what.

AC-coupled retrofits work with most modern systems. DC-coupled retrofits require careful integration. We diagnose during your site visit — no guesses.

Most string inverter systems

SolarEdge, SMA, Fronius, and Enphase microinverter systems from 2014 onward typically retrofit cleanly with an AC-coupled FranklinWH or IQ Battery.

Older inverters (pre-2014)

Some legacy inverters (early SunPower, Power-One, original Enphase M-series) require replacement before a battery can integrate. We diagnose during the site visit.

Microinverter systems

Enphase IQ6 and IQ7 systems pair best with the Enphase IQ Battery 5P for sunlight-backup capability and per-panel monitoring.

Retrofit-friendly batteries

Three batteries we retrofit weekly.

FranklinWH is the workhorse. Enphase 5P is the Enphase-system pick. Powerwall 3 is the case-by-case option that often pairs with a system upgrade.

Tier 1 battery

FranklinWH aPower

AC-coupled and inverter-agnostic. Best fit for most retrofits — works with nearly any existing string inverter or microinverter system without inverter replacement.

Capacity
13.6 kWh modular
Warranty
15 yr · 80% throughput
Tier 1 battery

Enphase IQ Battery 5P

AC-coupled stackable battery purpose-built for Enphase microinverter systems. Per-module monitoring and sunlight-backup capability.

Capacity
5 kWh per unit · stackable
Warranty
15 years
Tier 1 battery

Tesla Powerwall 3

Hybrid solar inverter and battery. DC-coupled, retrofits are case-by-case — usually requires replacing the existing string inverter. Best fit when paired with a system upgrade.

Capacity
13.5 kWh per unit
Warranty
10 years
Our approach

Our process,
refined through
9,000 installs.

Design
01.

Design

A 15-minute call, then a remote or on-site visit. Aurora-based design, panel and battery brand named on the proposal.

Build
02.

Build

Permits filed, utility interconnection submitted, and equipment staged at our Bristol warehouse.

Install
03.

Install

Local crew, local trucks. Most homes finished in 2 – 3 days. Final inspection scheduled before we leave.

Perform
04.

Perform

PTO from your utility, ITC and rebate paperwork filed, and 25 years of local service after the system goes live.

Your incentive stack

Federal, state, and utility
stacked.

On a typical $30K install in Connecticut, the total incentive stack lands between $13,000 and $17,000. We file every form with you.

Federal ITC

30%

Tax credit, claimed in the year of install. Locked through 2032.

CT ESS battery rebate

Up to $7,500

One-time check from CT Green Bank, paid through your installer.

Net metering

Full retail

1:1 offset on what your panels send back to Eversource or UI.

CT property tax exemption

$300 – $700/yr

System value excluded from your assessment. Sales tax also exempt.

Where we work

9,000+ rooftops across three states.

Connecticut, Massachusetts, and Rhode Island. Every pin is a Teamsun install. We're licensed in ME, NH, VT, and FL too.

CT · 5,400+ installs MA · 2,900+ installs RI · 700+ installs
Check your town
What customers say

Trusted by homeowners
who value quality.

“Teamsun was the only crew that walked the roof, named the panel brand, and answered every question without checking with someone. Same lead tech came back a year later when I added a battery.”
Robert P. Homeowner · Glastonbury, CT
“Three of my neighbors had Teamsun, so I called them. The crew was on my street five days after I signed.”
David L. Homeowner · West Hartford, CT
“They knew the historic district secretary by first name. Saved us six weeks on permitting alone.”
The Hwang family Homeowners · Glastonbury, CT
“Same lead tech who installed it came back four years later to swap an inverter under warranty. No charge, no excuses.”
Sandra M. Homeowner · Worcester, MA
Retrofit FAQ

Questions homeowners ask about retrofitting.

My solar was installed by a company that no longer exists. Can you still retrofit?

Yes. We do not need the original installer to be in business. We pull your inverter make and model from the equipment label, run a compatibility check, and design the retrofit around what you have.

Will adding a battery void my existing solar warranty?

For AC-coupled retrofits with FranklinWH or Enphase, no — your existing inverter and panel warranties remain intact because we do not modify them. For DC-coupled retrofits (Tesla Powerwall 3) that require an inverter swap, we transition warranty coverage to the new equipment as part of the project.

How long does a battery retrofit take?

3 – 6 weeks from contract to commissioned. Site visit and design lock takes 1 week, electrical permit and utility update takes 2 – 4 weeks, and the install itself is 1 – 2 days on-site.

Do I qualify for CT ESS or MA Connected Solutions on a retrofitted battery?

Yes — both programs accept retrofitted batteries on existing solar systems. The enrollment paperwork is identical to a new install. Teamsun handles every form.

How much does a retrofit cost compared to a new install?

Retrofit pricing depends heavily on your existing system. AC-coupled retrofits onto modern string-inverter or microinverter systems are typically 20 – 30% less than a comparable new install because no PV work is required. DC-coupled retrofits requiring inverter replacement run closer to a full system upgrade.

Can I add a battery without solar?

Yes — standalone battery installs (no solar required) are eligible for the 30% federal ITC and CT ESS / MA Connected Solutions enrollment. We install standalone batteries for backup-only use cases regularly.

Will the battery back up my whole house during an outage?

A single 13.6 kWh battery (FranklinWH or Powerwall 3) typically backs up essential loads — fridge, lights, internet, well pump, gas-furnace blower — for 12 – 36 hours. Whole-home backup including AC and electric heat usually requires two stacked units.

What if my electrical panel is not battery-ready?

A small percentage of older homes need a service panel upgrade to add a battery. We diagnose during the site visit and quote both as part of one project — no surprises later.

Does Teamsun service the retrofitted system long-term?

Yes. Once we retrofit a battery, that system is on our service list. You call our Bristol office and a person picks up — same as if we had installed the original solar.

How do I know if a retrofit makes financial sense for me?

Three quick signals: you have time-of-use utility rates, you live in CT or MA where demand-response programs pay, or you have outage frustration that solar alone does not solve. We run the math during the site visit using your last 12 months of utility data.

Free quote

Ready to go solar?
Request a quote today.
It's free.

A 15-minute call with a designer who knows your town. No closer on the line. No follow-up unless you ask for one. $0 down options available.

Request a free quote 203-903-4091

Bristol office

A person picks up.
Mon – Fri, 8am – 6pm.

Service area

CT · MA · RI
Licensed in ME · NH · VT · FL

Free terms

$0 down, free consult.
No credit card required.