I need a solar inverter that charges a backup battery during a grid outage.

Yes — what you’re looking for is generally called a hybrid solar inverter / inverter-charger. It can:

• Convert solar power to household AC.
• Charge a 48V battery from the solar panels.
• Charge the battery from the grid when desired.
• Automatically switch to battery power when the grid fails.
• Continue charging the battery from solar during the outage, assuming the inverter is designed for backup/off-grid operation.

For a typical U.S. home with 120/240V service, I'd focus on 48V battery systems with 120/240V split-phase output.

Good options

• SOL-ARK 12kW Hybrid Inverter - $4,499.00 (Home Depot + others)

• EG4 18KPV Hybrid Inverter - $4,444.44 (Off-Grid Source)

• AIMS Power 9.6kW Hybrid Inverter Charger - $1,990.00 (Walmart - AIMS Corp. + others)

• WattCycle 12kW Hybrid Inverter - $1,599.99 (WattCycle)

• SOL-ARK 12K-2P — premium, very capable whole-home option. It integrates the inverter, battery charging, solar MPPTs and backup functions. Current shopping results are around $3,850–$4,500.

• EG4 18KPV — another strong whole-home choice, with 12kW continuous output and up to 18kW of PV input.

• AIMS 9.6kW — somewhat less expensive and well suited if you don't need extremely large loads.

• WattCycle 12kW — substantially cheaper and advertises 120/240V split-phase, 48V batteries, 24kW maximum PV input and a 250A charger. It also lists UL 1741 testing/certification, but I'd verify the exact certification and permitting requirements with your installer/AHJ before using it for a permanently interconnected home system.

The important part: sizing

I wouldn't choose the inverter based simply on your solar-panel wattage. We need to size three things separately:

1. Inverter power (kW) — how many appliances you can run simultaneously.
2. Battery capacity (kWh) — how many hours you can run them during an outage.
3. Solar input (kW) — how quickly solar can recharge the battery.

For example, a 10–12kW inverter + 10–20kWh LiFePO₄ battery is a very reasonable starting point for many homes. If you only want essentials—refrigerator, lights, internet, furnace blower, etc.—you may need considerably less.

If you tell me your approximate budget, whether this is for your whole house or just essential circuits, and what you want to keep running during an outage (HVAC, well pump, electric stove, water heater, etc.), I can narrow this down to the right inverter and battery size.

To keep your backup batteries charged by solar panels during a grid outage, you need a hybrid solar inverter (sometimes called an all-in-one hybrid inverter/charger). Unlike standard grid-tied inverters—which automatically shut down during a blackout for safety reasons—hybrid inverters can isolate your home from the grid, power your essential loads, and safely route solar energy back into your storage batteries.[1][2]

Top-tier hybrid inverters capable of seamless battery charging and backup during grid outages include:

Widely considered the gold standard for robust whole-home backup. It features a lightning-fast transfer time, massive surge capacity (easily starts heavy appliances like a 5-ton AC unit), and an all-in-one pre-wired design that handles solar, battery, and generator integration smoothly.[1]

A high-power, highly scalable 48V split-phase hybrid inverter. It accepts massive PV input, features multiple MPPTs for flexible solar array configurations, and works seamlessly with 48V LiFePO4 battery banks for off-grid or emergency backup.

If you prefer a modular, semi-portable, or fast-install ecosystem rather than traditional wall-mounted electrical stacks, this unit paired with a smart home panel provides automatic sub-20ms switchover and heavy-duty solar/battery integration.[1]

A premium choice if you are looking for European engineering and system-design flexibility. It offers everything from a basic backup plug for essential loads up to full three-phase whole-home backup capabilities when paired with the right switches and batteries.

To help narrow down the best model for your setup, could you tell me:

• Do you need whole-home backup or just critical loads (refrigerator, lights, Wi-Fi)?
• What is your current or planned solar array size (in kilowatts)?
• Do you already own a specific battery model or voltage (e.g., 48V or high-voltage)?

Yes — what you’re looking for is a hybrid solar inverter / inverter-charger. It can:

• Convert solar power to household AC.
• Charge a battery from solar.
• Charge the battery from the grid when desired.
• Automatically switch to battery power when the grid fails.
• Keep selected circuits—or potentially the whole house—running during an outage. Hybrid inverters are specifically designed for this grid/solar/battery/backup combination.

Good options

• Sol-Ark 5K Hybrid Inverter - $2,080.99 (Renewable Outdoors)

• EG4 FlexBOSS18 13kW Hybrid Inverter - $2,999.00 (Renewable Outdoors)

• Solis S6 9.6K 48V Hybrid Inverter - $4,710.00 (self2solar)

• Renogy 48V 3500W Inverter Charger - $769.99 (The Home Depot)

• Sol-Ark 5K — a strong choice for a smaller residential backup system; 48V battery architecture and 120/240V capability.

• EG4 FlexBOSS18 — better if you want substantially more power for whole-house loads; it's a 48V split-phase hybrid system.

• Solis S6 9.6K — a good middle ground for a larger residential installation.

• Renogy 48V 3500W — more budget-oriented, particularly for essential loads rather than an entire house.

For a U.S. home, I would generally favor a 48V split-phase hybrid inverter + LiFePO₄ battery if you're building a system from scratch. 48V is widely used for residential hybrid systems, and LiFePO₄ is currently the dominant battery chemistry for this type of storage.

The important part is sizing the inverter and battery together. For example, a 5 kW inverter doesn't mean a 5 kWh battery: 5 kW is instantaneous power, while kWh is how long the battery can supply that power.

If you tell me (1) your solar-panel wattage, (2) whether you want the whole house or just essentials during an outage, and (3) roughly how many hours you want backup, I can recommend the appropriate inverter size and battery capacity.

A hybrid solar inverter manages your solar panels and charges your backup battery during a grid outage.[1]

Watch this overview to understand how whole-home hybrid and backup systems manage outages and solar charging:

9:49 EASIEST Grid-Tied Solar Battery Back Up System 49K views  · 7 months ago YouTube · Martin Johnson - Off Grid Living

Key Features to Look For

• Hybrid Capability: Standard grid-tied inverters shut off during blackouts for safety. You specifically need a "hybrid" or "off-grid/backup" inverter that isolates your home (anti-islanding) to safely power and recharge batteries using solar panels when the grid is down.
• Transfer Time: Look for a fast switch time (measured in milliseconds) so your lights and computers do not flicker or reset when the grid drops.
• Battery Voltage Compatibility: Make sure the DC voltage of the inverter matches your battery bank (commonly 48V for whole-home setups).

If you want to narrow down your choices, let me know:

• What is your estimated peak wattage or daily energy usage?
• Do you already own a specific battery model or brand?

To keep your essential appliances running and your batteries charged during a blackout, you need a hybrid solar inverter (sometimes called an all-in-one solar inverter-charger). Unlike standard grid-tied inverters that shut down for safety when the power grid goes down, a hybrid inverter isolates your home (via an automatic transfer switch/UPS function) and uses your solar panels to actively juice up your battery bank while feeding your home loads.[1][2][3]

Top-performing options on the market depend on your power scale and budget:

• Sol-Ark 12K-2P / 18K-2P Go to product viewer dialog for this item.: Widely considered the gold standard for whole-home resilience. It's an all-in-one heavy-hitter featuring lightning-fast switching, massive surge capacity, generator integration, and seamless compatibility with a wide range of 48V lithium batteries. You can view specs or options via Home Depot's Sol-Ark 12kW Listing.[1][2]
• EG4 12kPV Hybrid Inverter Go to product viewer dialog for this item.: An extremely popular, cost-effective choice for robust residential backup. It provides split-phase 120/240V power, rapid <10ms transfer time during grid failures, closed-loop communication with prominent lithium batteries, and high scalability. Check retailer availability on ShopSolar.com's EG4 12K PV Page.[1]
• ECO-WORTHY 5kW / 10kW All-In-One Inverter Go to product viewer dialog for this item.: A budget-friendly, highly integrated option ideal for smaller setups, cabins, or essential-circuit backups. It features dual MPPT controllers and built-in UPS switching to jump into battery mode the moment the grid drops. Explore details on the Eco-Worthy Official Store.[1][2]

To help narrow down which inverter fits your setup, tell me:

• Do you want to back up just essential circuits (fridge, lights, Wi-Fi) or your entire home?
• What is your approximate solar array size (in kW) or planned battery voltage/capacity?

Yes — what you want is a hybrid solar inverter/charger, not a standard grid-tied solar inverter.

It should:

• Use solar panels to power the house and charge the battery.
• Keep the battery charged from the grid when appropriate.
• Automatically disconnect from the grid during an outage and run your backup loads from battery + solar.
• Ideally provide 120/240V split-phase output for a U.S. home.
• Support a lithium/LiFePO₄ battery with BMS communication.

Good options

• EG4 FlexBOSS18 13kW Hybrid Inverter - $2,999.00 (Renewable Outdoors)

• Solis S6 12K 48V Hybrid Inverter - $5,140.00 (self2solar)

• Sol-Ark 15K-2P Hybrid Inverter - $5,199.00 (Walmart - Premier Goods Trading Co)

• EG4 6000XP 48V Inverter Charger - $1,549.00 (US Solar Supplier)

• EG4 FlexBOSS18 — a strong choice for whole-home backup; 48V split-phase and UL1741 certified.

• Solis S6 12K — particularly interesting if you want a modern hybrid system; the S6 family supports 9.6–16 kW, 200A pass-through, and battery storage.

• Sol-Ark 15K-2P — premium option if you want a powerful, expandable system.

• EG4 6000XP — better suited to essential-load backup rather than a large whole-house system.

For example, the EG4 12kPV is a 48V split-phase hybrid inverter with up to 12 kW of solar input, 8 kW continuous output, generator support, and UL1741/SA/SB certifications.

The battery is just as important

The inverter's kW rating determines how much you can run simultaneously; the battery's kWh capacity determines how long you can run it.

For example, a 10 kWh battery theoretically provides about:

• 1 kW load → ~10 hours
• 2 kW → ~5 hours
• 5 kW → ~2 hours

Real-world runtime will be somewhat lower because of inverter losses, battery reserve, temperature, etc.

If you tell me (1) your solar-panel wattage, (2) which appliances you want running during an outage, and (3) roughly how many hours/days of backup you want, I can size the inverter and battery and recommend a specific setup.

Yes — what you’re looking for is a hybrid solar inverter / battery inverter that can operate in backup (islanding) mode. A normal grid-tied inverter will shut down when the utility fails; a properly designed hybrid system can keep selected circuits—or the whole house—powered from the battery and solar.

Good options

• Sol-Ark 15K Hybrid Inverter - $5,299.00 (Renewable Outdoors)

• Solis S6 10kW Hybrid Inverter - $2,059.00 (self2solar)

• Solis S6 7.6kW Hybrid Inverter - $1,469.00 (self2solar)

• Solis S5 5kW Hybrid Inverter - $942.11 (VoltaconSolar)

• Sol-Ark 15K — a strong choice if you want whole-home 120/240V backup, substantial surge capability, and flexibility with batteries. The current listing shows 12 kW battery output and 200A pass-through.

• Solis S6 — worth considering for a new solar + battery installation; it comes in several power levels and is designed around energy-storage applications.

• 5–7.6 kW class — appropriate if you're backing up essential loads rather than trying to run the entire house.

For a California home, I'd generally favor a UL-listed, grid-interactive hybrid system from an established manufacturer over the very inexpensive generic 48V inverters. A professionally installed system also needs the appropriate transfer/islanding equipment and battery compatibility; the inverter, battery BMS, solar array, and electrical panel all have to work together.

The battery size is just as important as the inverter. For example, a 10 kWh battery can theoretically supply a 5 kW load for about two hours, before accounting for conversion losses and reserve capacity.

If you tell me (1) whether you already have solar, (2) your existing inverter model, (3) what you want to keep running during an outage—AC, refrigerator, well pump, etc.—and (4) roughly how many hours/days of backup you want, I can narrow this down to the right inverter + battery combination and current prices.

To keep your home powered and your batteries charging via solar panels during a grid outage, you need a hybrid solar inverter (sometimes called a multi-mode or all-in-one inverter charger). Standard grid-tied inverters automatically shut down during a blackout for safety reasons (anti-islanding), whereas hybrid inverters can isolate from the grid, power your home, and actively pull energy from your solar array to recharge your backup battery bank.

Top-tier options available on the market range from whole-home industrial systems to modular all-in-one units:

Add to list Sol-Ark 15K-2P or 12K-2P Hybrid Inverter – Widely considered the gold standard for robust, whole-home residential backup. It features lightning-fast switchover times (~ 5 ms), massive surge capacity, high-voltage PV inputs, and seamless integration with a wide variety of 48V lithium battery banks.[1][2]

Add to list Tesla Powerwall 3 – An integrated all-in-one unit combining the battery and a high-efficiency solar inverter into a single sleek package designed specifically for seamless backup.

Add to listEG4 FlexBOSS21 – A next-generation split-phase hybrid inverter engineered for heavy-duty whole-home backup and flexible solar harvesting, offering high PV capacity and native 48V battery compatibility.

Add to list EcoFlow DELTA Pro Ultra X – A modular, highly scalable plug-and-play style whole-home backup solution that pairs high-output inverter capabilities with expandable LFP battery stacks and rapid auto-switchover.[1]

Add to list Sungrow Hybrid Inverters – Excellent all-around grid-interactive hybrid units providing flexible battery pairing and reliable dedicated emergency backup outputs.

To help narrow down the best choice, let me know:

• Do you need whole-home backup (running heavy loads like central AC) or just critical loads (refrigerator, lights, internet)?
• What is your budget range or preferred battery size?
• Do you already have existing solar panels , or is this a completely new build?

Yes — what you want is a hybrid solar inverter / inverter-charger. It can:

• Run your house from the grid normally.
• Charge the battery from solar and/or the grid.
• Automatically switch to the battery when the grid fails.
• Continue using solar to charge the battery during an outage, depending on the system design.
• Provide 120/240V split-phase power for typical U.S. homes.

Good options I found

EG4 FlexBOSS18 13kW Hybrid Inverter

$2,999.00

Solis S6 12K 48V Hybrid Inverter

$5,010.00

BigBattery APEX 6.5K Hybrid Inverter

$1,490.00

EG4 6000XP 48V 6kW Inverter/Charger

$1,549.00

My picks:

1. EG4 FlexBOSS18 — strong choice if you want substantial whole-home backup. It's a 48V split-phase hybrid inverter with UL 1741 certification.
2. Solis S6 — a more conventional residential hybrid system; its U.S. model provides native 120/240V backup and can supply up to 11.4 kW continuously.
3. BigBattery APEX 6.5K — less expensive option if you're primarily backing up essential circuits rather than the entire house.
4. EG4 6000XP — another 6 kW-class option worth considering for a 48V battery bank.

For a higher-end system, the Sol-Ark 18K is another excellent candidate. It supports 48V batteries, 120/240V split phase, solar, battery, generator and grid integration, with UL 1741 SA certification. Home Depot currently lists it around $6,699 for the inverter alone.

One important distinction

If by "charges a backup battery during a grid outage" you mean the solar panels should continue charging the battery while the utility grid is completely down, make sure you buy a true hybrid/off-grid-capable inverter, not merely a grid-tie inverter with a battery.

Also, don't size the inverter just by your home's service size. For example, a 6 kW inverter can handle roughly 6,000 W of continuous load, while an 18 kW unit can handle substantially more. Your battery's kWh capacity determines how long you can run those loads.

If you tell me (1) your solar-panel wattage, (2) whether you want whole-house or just essentials, (3) your desired backup time, and (4) your approximate budget, I can narrow this down to 2–3 specific inverter + battery combinations.

To keep your backup battery charged via solar panels during a grid outage, you need what is known as a hybrid solar inverter (or a multi-mode inverter/charger). Unlike standard grid-tied inverters that automatically shut down during a blackout for safety reasons, a hybrid inverter isolates your home from the grid, keeps powering your loads, and routes surplus solar energy straight into your battery bank.

Top Hybrid Inverter Recommendations

Sol-Ark 15K / 8K — Widely considered the gold standard "workhorse" for residential backup. It has a massive surge capacity, handles whole-home backup easily (including heavy loads like well pumps or AC units), switches instantly during an outage, and integrates seamlessly with various 48V battery brands.

Tesla Powerwall 3 — An all-in-one unit featuring an integrated solar inverter and massive energy storage capacity. It's sleek, highly efficient, and automates whole-home or critical load backup smartly.

EG4 (18kPV or FlexBOSS21) — A very popular, cost-effective 48V split-phase hybrid choice for robust residential backup and high PV input capacity, well-supported by the DIY and professional solar community alike.

Enphase IQ8 Series with IQ Battery — Instead of a single central box, Enphase uses microinverters at the panel level coupled with an Enphase storage system. It offers unique grid-forming capabilities and modular expansion.

SolarEdge Energy Hub — A great DC-optimized string inverter choice if your roof layout has partial shading issues and you want streamlined battery management in a single unit.

Key Factors to Keep in Mind Before Buying

• Battery Compatibility: Hybrid inverters are often picky about communication protocols. Always check if the inverter officially supports the specific brand and voltage (e.g., 48V vs. high-voltage proprietary batteries) of the battery you plan to use.
• Whole-Home vs. Critical Loads Backup: Ensure the continuous wattage output of the inverter can handle what you intend to run. Backing up an entire home requires a 9kW to 15kW+ unit, whereas a smaller 5kW–6kW inverter may require a dedicated sub-panel for critical loads (fridge, lights, Wi-Fi).
• Split-Phase Output: If you live in North America and use standard US household power, make sure the inverter explicitly states it outputs 120V/240V split-phase so it can drive your large 240V appliances.[1][2]
• Code and Certifications: Look for UL1741 (or UL1741SB) certification, which is universally required by US utility companies and inspectors for grid-interactive backup systems.[1][2][3]

To help narrow down the exact model you need, could you share:

• Do you want to back up your entire house or just critical appliances?
• Do you already own or have a specific battery brand in mind?