In short: a battery pays off with solar when your utility pays little for exported power, when evening electricity is expensive, when a rebate helps, or when you want backup in outages. With full retail net metering and a reliable grid, it’s mostly peace of mind. Installed batteries averaged about $1,159 per kWh on EnergySage in 2026.
This page helps you decide whether to add storage to a new or existing solar system: when it makes money, when it doesn’t, how batteries connect (AC or DC coupling), how to size one and what it costs. For brands, runtimes and battery-only setups, our home batteries section goes deeper.
Solar plus battery at a glance
- Popular now: 46% of new U.S. home solar systems in Q2 2026 came with a battery (Wood Mackenzie, September 2026).
- But mostly in some places: in 2024, 57% of new California home solar systems had a battery, versus 8% across all other states combined (Berkeley Lab).
- Typical size: 13.5 kWh median, most between 10 and 20 kWh (Berkeley Lab, 2024 installs).
- Cost: about $1,159 per kWh installed, or $15,647 for a 13.5 kWh battery (EnergySage, updated August 2026).
- No federal homeowner credit for batteries installed after December 31, 2025 (IRS, 25D).
Why solar alone doesn’t keep your lights on
Most people are surprised by this. A standard grid-tied solar system shuts down when the grid goes down; the Department of Energy explains that inverters disconnect during grid disruptions. To keep power during an outage, you need a battery plus equipment that separates your home from the grid (often called a gateway, system controller or backup switch). That’s often the main reason people add storage in outage-prone states. In 2024, U.S. customers averaged about 11 hours without power, the most in ten years, largely because of hurricanes (EIA).
When a battery pays off with solar
| Your situation | Does a battery help? | Why |
|---|---|---|
| Net billing: exports credited below retail (California, Arizona and other states) | Often yes | Storing midday solar and using it in the evening is worth more than exporting it cheaply |
| Time-of-use or hourly pricing with pricey evenings | Often yes | The battery covers the expensive hours |
| A battery rebate or demand-response program | Yes, if you meet the rules | Upfront rebates or yearly payments cut the net cost |
| Frequent or long outages | Yes, for backup | Solar can recharge the battery during multi-day outages |
| Full retail net metering and a reliable grid | Rarely on money alone | The grid already acts as a free “battery” for your exports |
Examples of programs we’ve checked:
- Illinois: ComEd pays a $300 per kWh rebate for a battery paired with solar, if you join its Hourly Pricing rate; Ameren Illinois ties its storage rebate to Peak Time Rewards or hourly pricing (Citizens Utility Board fact sheet, March 2026). See Illinois.
- Connecticut: the Energy Storage Solutions program pays an upfront incentive plus yearly performance payments for letting the utility use your battery at peak times (program rules from April 1, 2026). See Connecticut.
- Massachusetts: ConnectedSolutions pays battery owners for summer peak events. See Massachusetts.
For backup, the states with the most outage minutes in 2024 were South Carolina (3,136 minutes per customer), North Carolina (1,441), Florida (1,322) and Texas (1,271), counting major storms (EIA-861). Each state page explains its net metering rules too.
AC-coupled vs DC-coupled batteries
Solar panels make DC power, your home uses AC, and batteries store DC. How the battery connects decides how many times the power is converted, and how easy it is to add to an existing system.
| AC-coupled | DC-coupled (hybrid inverter) | |
|---|---|---|
| How it connects | The battery has its own inverter and connects on the AC side, next to your existing solar inverter | Panels and battery share one hybrid inverter on the DC side |
| Best for | Adding a battery to solar you already have | New solar-plus-battery systems, or when the old inverter needs replacing anyway |
| Efficiency | Solar power that’s stored gets converted more times, so a little more is lost | Fewer conversions when charging straight from the panels |
| Examples | Enphase IQ Battery 10C, made to work with Enphase IQ and M Series microinverters | Tesla Powerwall 3, which has a built-in solar inverter for up to 20 kW of panels |
Either way works well. What matters more is that the battery is compatible with your inverter and your utility’s rules, and that it’s installed by someone certified for that brand. Ask the installer which setup they propose for your home and why.
How to size a battery for your solar
Start with the job you want the battery to do. Two numbers matter: capacity (kWh, how much energy it stores) and power (kW, how much it can deliver at once, including the surge to start motors).
- Evening self-use (net billing or time-of-use): size to the power you use from late afternoon to bedtime. Most home batteries installed in 2024 held 10 to 20 kWh, and the median could run for 2 hours at full power (Berkeley Lab).
- Backup for essentials: a fridge, freezer, lights, Wi-Fi, phones and a sump pump can use roughly 3.5 kWh a day in our worked example in how long home batteries last. One battery plus daytime solar recharging can carry essentials through a long outage.
- Whole-home backup: the average U.S. home used about 29.6 kWh a day in 2022 (EIA), and central air, well pumps and electric ranges need high surge power. Expect two or three batteries and a check of each one’s starting current: Tesla lists 185 LRA for Powerwall 3, Enphase up to 90 A for the IQ Battery 10C.
Our battery backup calculator turns your appliances and hours into a capacity estimate. Treat it as a starting point; the installer’s load calculation is what counts.
What adding a battery to solar costs
| Brand (EnergySage, H1 2026 quotes) | Average $/kWh | Typical size | Typical installed price |
|---|---|---|---|
| Tesla | $967 | 13.5 kWh | $13,055 |
| Enphase | $1,429 | 10 kWh | $14,290 |
| FranklinWH | $1,232 | 15 kWh | $18,480 |
Across all brands, EnergySage’s average was $1,159 per kWh, or $15,647 installed (updated August 2026); its H1 2026 market report put quotes at $1,130 per kWh, partly due to new foreign-sourcing rules. Berkeley Lab found solar-plus-battery systems had a median price $1.7 per watt higher than solar alone in 2024. Adding a battery later usually means more labor and wiring than including it from the start, and an older inverter may need replacing. Full cost detail: home battery cost.
The federal 30% credit (25D) ended for batteries installed after 2025. If you lease, the leasing company may still claim a business credit and pass some value on to you (EnergySage). Local rebates like Illinois’ $300 per kWh can make a real dent: on a 13.5 kWh battery that’s $4,050 (our arithmetic).
Battery with solar, battery alone, or a generator?
Solar is what turns a battery from a one-time reserve into something that refills itself. Without panels, a battery charges only from the grid, so in a long outage it runs down and stays down; EnergySage notes that payback for a standalone battery is hard to calculate. With solar, a sunny day can refill much of what you used overnight, though cloudy stretches and winter cut that sharply. If you don’t have solar and mostly want backup, compare home batteries without solar and the generator vs home battery guide: a standby generator runs as long as fuel flows, but it burns fuel, needs regular service and must stay outdoors. Some homes combine both, using the battery for short outages and quiet nights and the generator for long storms.
Installation: what to expect
Adding storage means a site visit, a design (which circuits are backed up), electrical permits, often a fire code review of where the battery goes, an inspection and an update to your utility interconnection. NREL found solar-plus-battery projects took about 3 months longer than solar alone in 2023. The full process, permits and installer certifications are in home battery installation. Choosing between a battery and a generator for outages? See backup power options.
Get help adding a battery to solar
Tell us about your solar (or plans), your utility and what you want the battery for. Tell us about your project and we will connect you with a licensed, independent installer who serves your area. It is free, there is no obligation, and only the installer you choose gets your details. How it works.
Solar battery storage questions
Is a solar battery worth it?
It depends on your utility and your goals. A battery pays best where exported solar earns less than retail, where evening rates are high, or where rebates such as Illinois’ $300 per kWh apply. If your utility credits exports at full retail and outages are rare, a battery is mainly for peace of mind. Run your numbers with your actual rate plan.
Can I add a battery to my existing solar system?
Usually, yes. Most retrofits use an AC-coupled battery that connects beside your current inverter, so the panels stay as they are. Check your interconnection agreement and any lease terms first, and ask whether your inverter is near the end of its warranty: if so, a hybrid inverter with DC-coupled storage might make more sense.
How many batteries do I need with solar?
For evening self-use or backing up essentials, one battery of about 10 to 15 kWh is common; the 2024 median was 13.5 kWh (Berkeley Lab). For whole-home backup with central air or a well pump, plan on two or three, sized for both energy and motor-starting surge. Our battery backup calculator gives a first estimate.
Will my solar recharge the battery during an outage?
Yes, if the system is designed for backup. The battery’s gateway or controller disconnects your home from the grid, then lets the solar keep running and charging the battery. Without that equipment, grid-tied solar shuts off in an outage. Confirm with the installer that your design supports solar charging while off-grid.
Is there a tax credit for solar batteries in 2026?
Not for homeowners who buy. The IRS says the 25D credit isn’t available for property placed in service after December 31, 2025. Leasing companies may still claim a business credit and pass some value on. State and utility rebates continue in places like Illinois and Connecticut; check your state page and incentives.
Sources
Wood Mackenzie/ACP U.S. Energy Storage Monitor (September 2026); Berkeley Lab, U.S. Distributed Solar and Storage: 2025 Data Update (October 2025); EnergySage battery cost pages (July and August 2026) and H1 2026 market report; IRS Residential Clean Energy Credit; U.S. DOE solar inverter basics; EIA Today in Energy (December 2025), EIA-861 2024 reliability data and residential use FAQ; Citizens Utility Board Illinois rebate fact sheet (March 2026); Energy Storage Solutions Connecticut program changes (2026); Enphase IQ Battery 10C data sheet; Tesla Powerwall 3 data sheet; NREL timeline report (November 2025). Checked October 3, 2026.