Solar batteries, explained
A battery turns daytime solar into nighttime power, backup during grid outages, and — in Texas — the key that unlocks the Oncor rebate. Here is how home storage works and how to size it right.
A solar battery stores surplus daytime solar to use at night or during an outage. In Texas it does three jobs: backup power during ERCOT grid events, self-consumption when your buyback rate is weak, and unlocking the Oncor rebate of up to $9,000 — which requires storage. Most home batteries today use safe, long-lasting LFP chemistry, hold 10–14 kWh each, and are sized to your goal (essentials-only vs. whole-home backup). The specs that matter are usable capacity, continuous power, round-trip efficiency, and warranty.
Why add a battery to solar
Solar panels only make power when the sun is up. A home battery stores the extra energy your panels produce during the day so you can use it at night, during a power outage, or when the grid is straining. Without storage, that surplus flows to the grid and you depend on your buyback plan to get credited for it. With storage, you decide when to use your own power.
There are three big reasons batteries have become mainstream:
Backup power
After high-profile grid failures, homeowners increasingly want to keep the lights, fridge, and AC running during outages. A battery does that automatically.
Utility rebates
Where offered, storage rebates require a battery. No battery, no rebate — which often pays for much of the battery itself.
Self-consumption
If your net-metering credit is low, storing and using your own power is worth more than exporting it cheaply.
How a solar battery works
A home battery is a stack of rechargeable lithium-ion cells, plus electronics that manage charging, safety, and how it talks to your solar system. During the day, surplus solar charges the battery; in the evening or during an outage, the battery discharges to power your home. A hybrid inverter (or the battery's built-in inverter) handles the conversions and decides, minute by minute, whether to pull from panels, battery, or grid.
The big technical choice is battery chemistry, because it drives safety, lifespan, and cost.
Two chemistries dominate home storage
LFP (lithium iron phosphate) is now the most common for home batteries — very safe, long cycle life, and tolerant of daily full use. NMC (nickel manganese cobalt) is more energy-dense (more storage in a smaller box) but runs hotter and is used in some older or more compact units. For most homes, LFP is the preferred choice today.
Battery types & how they connect
Beyond chemistry, batteries differ in how they tie into your solar system — which affects efficiency and how easily one can be added to an existing array.
- DC-coupled. The battery connects on the DC side, before conversion to AC. Fewer conversions means slightly higher efficiency — ideal when you install solar and storage together.
- AC-coupled. The battery has its own inverter and connects on the AC side. Easier to add to an existing solar system, with a small efficiency trade-off.
- Whole-home vs. partial backup. A whole-home setup backs up everything; a partial (critical-loads) setup backs up essentials like the fridge, some lights, and internet — cheaper and often enough.
- AC battery units like the Tesla Powerwall bundle the battery and inverter together; modular systems like Enphase IQ let you stack capacity in smaller increments.
Common home batteries: Tesla Powerwall, Enphase IQ Battery, FranklinWH, LG, and SolarEdge. The Powerwall is the most recognized name, and Powerwall-certified installers are widely available.
How to size a battery
Battery size is measured in kilowatt-hours (kWh) of energy (how much it stores) and kilowatts (kW) of power (how much it can deliver at once). You need enough of both: energy to last through the evening or an outage, and power to actually run what is plugged in.
- Decide your goal. Backup essentials only, or run the whole house (including AC) through an outage? That sets the size.
- Check your evening usage. How many kWh you use after sunset determines how much storage covers a normal night.
- Match power to your big loads. Central AC and EV charging need high continuous kW — undersized power means the battery cannot run them even if it has energy left.
- Plan for incentives. Size the system so it qualifies for any local storage rebates with a participating installer.
The battery specs that matter
| Spec | What it means | Good range |
|---|---|---|
| Usable capacity (kWh) | Energy you can actually use per charge | 10–14 kWh / unit |
| Continuous power (kW) | How much it can run at once | 5 kW+ |
| Depth of discharge | Share of capacity safely usable | 90–100% (LFP) |
| Round-trip efficiency | Energy returned vs. stored | 90%+ |
| Cycle life / warranty | Charge cycles & years guaranteed | 10 yr / ~70% retained |
Solar battery brands worth knowing
A handful of brands dominate home storage, and they differ in capacity, power output, how they connect, and — importantly — warranty terms. Here are the names you will actually be quoted in DFW.
| Brand | Usable capacity | Continuous power | Warranty |
|---|---|---|---|
| Tesla Powerwall 3 | ~13.5 kWh | 11.5 kW | 10 yr |
| Enphase IQ Battery 5P | 5 kWh (stackable) | 3.84 kW | 15 yr |
| FranklinWH aPower | 13.6 kWh | 10 kW | 12 yr |
| LG / others | ~10–16 kWh | 5–7 kW | 10 yr |
| SolarEdge Home | ~10 kWh | 5 kW | 10 yr |
Nearly all current home batteries use safe, long-life LFP chemistry. Specs are representative 2026 figures — confirm exact numbers on your proposal.
Tesla Powerwall 3
The most recognized home battery, with a built-in hybrid inverter and the highest continuous power output in its class.
Pros
- High 11.5 kW output — can start a big AC unit
- Built-in solar inverter (fewer parts)
- Strong app & huge installer network
Cons
- 10-year warranty trails some rivals
- Best value only with Tesla’s ecosystem
Enphase IQ Battery
A modular system you stack in 5 kWh increments, with the longest mainstream warranty at 15 years.
Pros
- 15-year warranty — best in class
- Modular: size it exactly to your needs
- Pairs seamlessly with Enphase micros
Cons
- Lower per-unit power output
- More units for whole-home backup
FranklinWH
A fast-rising whole-home system praised for smart energy management and strong output.
Pros
- Big 13.6 kWh capacity, 10 kW power
- 12-year warranty
- Excellent whole-home management
Cons
- Newer brand than Tesla/Enphase
- Fewer certified installers so far
LG, SolarEdge & others
Solid alternatives often quoted when they match your existing inverter brand.
Pros
- Integrate neatly with same-brand inverters
- Competitive pricing
- Proven LFP packs
Cons
- Mid-pack power & capacity
- 10-year warranty is the norm
Battery warranties: what to expect
A battery warranty is more nuanced than a panel’s because a battery wears as you use it. Good coverage protects you on three fronts at once — time, usage, and how much capacity is left at the end.
Years covered
Most home batteries are warrantied 10 years; Enphase leads at 15. This is the headline number — but read the other two.
Retained capacity
The guarantee that it still holds ~70% of original capacity at the end of the term. Higher is better.
Throughput / cycles
Some warranties also cap total energy (MWh) or cycles. With daily solar cycling, make sure the cap exceeds your real use.
| Warranty term | What it means | Typical | Best |
|---|---|---|---|
| Years | Calendar coverage | 10 yr | 15 yr |
| Retained capacity | Capacity left at end of term | 70% | ~80% |
| Cycle / throughput cap | Limit on total energy used | Varies | Unlimited cycles |
| Workmanship (installer) | The installation itself | 10 yr | 25 yr |
What to check before you sign
- Unlimited cycles? Some warranties stay valid only up to a set throughput. For daily solar use, “unlimited cycles” coverage is the gold standard.
- Retained-capacity number. 70% is standard; a guarantee closer to 80% means more usable storage in year 10.
- Labor included? Confirm the warranty pays to replace a failed unit, not just ship one.
- Whose name is on it? A reputable installer files battery claims for you and stands behind the install with their own workmanship warranty.
- Bankable brand. Storage is newer than panels — favor manufacturers with the scale to honor a 10–15 year promise.
The warranty shapes the value
Because a battery’s payback depends on it lasting, a longer, cycle-unlimited warranty with higher retained capacity is worth real money — sometimes more than a slightly lower sticker price. Weigh it alongside the battery cost when you compare quotes.
Batteries & storage incentives
This is where local incentives can change the math: some utilities and states offer storage rebates that require qualifying battery storage installed by a participating contractor. Where available, these can offset a large share of the battery's cost, making storage far more affordable than the sticker price suggests — which is why we tell readers to ask every installer about rebates they design solar-plus-battery systems around.
The 2026 reality
With the 30% federal tax credit expired, local incentives matter more than ever. A battery paired with any local storage rebate, favorable net metering, and backup protection during grid events is one of the strongest cases for solar right now. See whether it pencils out in our is-solar-worth-it guide.
Frequently asked questions
Do I need a battery with my solar panels?
What is the difference between LFP and NMC batteries?
How big a battery do I need for my house?
How long do solar batteries last?
Can a battery qualify for storage rebates?
Get matched with installers who design rebate-ready battery systems
Want backup power and the Oncor rebate? Up to four independently reviewed installers will size a battery to your home and quote it accurately. Upload a recent bill for an exact number.
- Pros who design rebate-eligible battery systems
- Upload a bill for an exact, accurate quote
- You choose who to hire — zero pressure