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10/02/2025
PG&E NEM 3.0 and Solar Batteries: How California Homeowners Can Maximize Savings in 2025
If you live in Northern California, you’ve probably heard of PG&E’s NEM 3.0 program and the changes it brought to solar customers in 2023. Many homeowners are now asking the same question: Is solar still worth it in 2025?
The short answer is yes — but the way you design your system matters more than ever. Under NEM 3.0, solar plus a battery is the winning combination for lowering bills, improving energy independence, and protecting your home during outages.
In this guide, we’ll break down what changed, how it affects your PG&E bill, and why batteries like the Tesla Powerwall 3, Enphase IQ 10C, and FranklinWH aPower are becoming essential for California homeowners.
What Changed Under PG&E’s NEM 3.0?
Under the previous program (NEM 2.0), homeowners earned near-retail credit for each kilowatt-hour they exported back to the grid. That meant solar panels alone could dramatically cut electricity bills — even without a battery.
With NEM 3.0, the value of exported electricity has been reduced by roughly 75% on average. Instead of being credited at close to the retail rate, exported power is compensated at the “avoided cost” rate, which is based on wholesale electricity prices.
Daytime exports (midday) are worth much less.
Evening energy (4 p.m. – 9 p.m.) is expensive, and that’s when solar panels aren’t producing.
This shift makes it harder to save money with solar panels alone, because you’re sending energy to the grid when it’s cheap and buying energy back when it’s expensive.
Why Batteries Are the Key to Savings
The new rules change the math — but they also highlight the value of solar battery storage. A battery allows you to:
Store excess solar power during the day.
Use it in the evening when PG&E’s rates are highest.
Reduce exports at low daytime rates.
Cut peak demand charges.
In other words, batteries help you keep more of the energy you generate, shifting your savings from export value to self-consumption value.
Even better: batteries provide backup power during blackouts — something many Bay Area homeowners worry about, especially after recent wildfire seasons and earthquakes.
Incentives in 2025: ITC + SGIP
The cost of adding a battery has dropped significantly thanks to federal and state incentives.
Federal Tax Credit (ITC):
The 30% credit applies to solar and batteries through at least 2032.
Stand-alone batteries also qualify (even if you already have solar).
California SGIP (Self-Generation Incentive Program):
Rebates are still available in 2025, especially for homes in fire-threat or outage-prone areas.
Typical savings: $2,000–$5,000 per battery.
Together, these incentives can cut the upfront price of a battery system by 30–40%, making it a financially smart move under NEM 3.0.
Real-World Example: Bay Area Home
Let’s look at a simple case study.
System size: 7 kW solar + 10 kWh battery
Without battery: Home exports most power at midday when rates are low. Monthly bill reduction: ~40%.
With battery: Stored energy offsets evening rates (often $0.40–$0.50/kWh). Monthly bill reduction: ~65–70%.
Over a 10-year span, the homeowner saves thousands more by adding a battery. And during PG&E outages, the battery provides reliable backup for lights, refrigeration, internet, and even essential medical devices.
Choosing the Right Battery: Tesla, Enphase, or FranklinWH?
At Ally Electric & Solar, we install several top battery brands. Each has strengths depending on your home’s needs.
Tesla Powerwall 3
High capacity (~13.5 kWh per unit).
Built for whole-home backup.
Sleek design, widely recognized.
Enphase IQ Battery 10C
Modular — you can add units over time.
Works seamlessly with Enphase microinverters.
Good option for homes starting with a smaller system.
FranklinWH aPower + aGate
Strong load management features.
Robust warranty and growing popularity in California.
Flexible for both new installs and retrofits.
Which is best? It depends on your household usage, backup needs, and budget. Our team helps homeowners compare options with clear side-by-side analysis.
Beyond Savings: Energy Independence and Resilience
While much of the NEM 3.0 discussion is about dollars and cents, the bigger picture is energy independence.
Batteries make you less dependent on PG&E’s shifting rate structures.
You gain peace of mind during outages — whether from wildfires, storms, or earthquakes.
Electrification trends (EVs, heat pumps, induction stoves) mean households will rely even more on electricity. Pairing solar with storage ensures you’re ready for that future.
Final Thoughts
PG&E’s NEM 3.0 has changed the landscape, but it hasn’t made solar a bad investment. It’s simply shifted the smart strategy from solar alone to solar plus battery storage.
With the 30% federal tax credit and SGIP rebates still in place, 2025 is an excellent year to invest. By adding storage, you can:
Maximize bill savings.
Gain resilience during outages.
Future-proof your home for the electrification era.
Call to Action
At Ally Electric & Solar, we specialize in designing solar + battery systems tailored to California homes. Whether you’re considering the Tesla Powerwall 3, Enphase IQ 10C, or FranklinWH aPower, our team can help you choose the right solution for your budget and lifestyle.
Contact us today for a free consultation and see how much you can save under PG&E’s new rules.
9/30/2025
Heat Pumps and Solar PV + Energy Storage: Are They a Good Match?
In recent years, homeowners across California and beyond have been exploring how to cut energy costs and reduce carbon emissions. Two technologies often come up in the same conversation: heat pumps and solar photovoltaic (PV) systems with energy storage (ESS). But how do these solutions relate, and is combining them really the right move for every household?
What Are Heat Pumps?
A heat pump is an electric appliance that can both heat and cool a home by transferring heat rather than generating it directly.
Heating mode: extracts heat from the outside air (even in cold weather) and moves it indoors.
Cooling mode: works like an air conditioner, removing heat from indoors and releasing it outdoors.
Because they move heat instead of producing it, heat pumps can achieve efficiencies of 200%–400%, compared to around 90% efficiency for electric resistance heaters or gas furnaces.
How Much Electricity Do Heat Pumps Use?
Electricity consumption depends on:
System size (measured in tons or BTUs).
Climate zone (mild Bay Area vs. colder mountain regions).
Home insulation and ducting.
On average:
A typical residential heat pump uses 2,000 to 4,000 kWh per year for heating and cooling.
That translates to 15%–30% of a household’s total annual electricity use in California.
In colder climates, usage can be higher, especially if backup resistance heating is needed.
For comparison, the average California household consumes about 6,500–7,000 kWh annually (without electric vehicles or large electrification loads). Adding a heat pump can increase that number by 25%–50%, depending on usage.
Why Pair Heat Pumps With Solar + ESS?
Offset Higher Electricity Demand
Without solar, switching from gas heating to a heat pump can cause a noticeable jump in your electric bill.
A properly sized solar PV system can offset most or all of the added consumption.
Take Advantage of Efficiency
Heat pumps are already efficient compared to gas furnaces or electric resistance heating.
Running them on solar power makes heating and cooling nearly emissions-free.
Resiliency With Storage
Energy storage systems (like Tesla Powerwall or Enphase IQ Battery) allow homes to keep heating or cooling during outages.
In California, where blackouts and Public Safety Power Shutoffs (PSPS) are a concern, this adds peace of mind.
Peak Shaving
Many utilities have time-of-use (TOU) rates, with higher costs in the late afternoon/evening.
Pairing a heat pump with storage lets homeowners shift usage and avoid peak pricing.
Is It Always a Good Solution?
It depends on your situation:
Good fit if:
You live in a region with mild winters (like most of California).
You’re planning to replace aging HVAC equipment or gas furnaces.
You want to reduce reliance on fossil fuels and improve indoor comfort.
You already have or plan to install solar PV with sufficient capacity.
Potential challenges:
In very cold climates, heat pumps may need backup resistance heating, which increases energy use.
Upfront costs for both a heat pump and a solar + storage system can be significant.
System sizing is critical — undersized solar arrays may not cover the added load.
The Bottom Line
Heat pumps and solar PV + ESS are complementary technologies. Heat pumps make homes more energy-efficient and all-electric, while solar plus storage ensures that extra demand is met sustainably and resiliently. For many California homeowners, combining the two is a smart long-term strategy — but the right solution depends on climate, home size, and budget.
Before making the switch, it’s best to consult with both a licensed HVAC contractor and a solar professional who can model your home’s projected energy use and recommend the right system size.
9/24/2025
Earthquakes Remind Us: Why Solar + Battery Systems Are Essential for Bay Area Homes
Just a few days ago, the Bay Area was shaken by a 4.3-magnitude earthquake near Berkeley/Pinole. While this was a moderate event, it served as an important reminder that we live in an earthquake-prone region where power outages can occur at any time. As an electrical engineer working with residential energy systems, I see firsthand how families are left vulnerable when the grid fails — and why solar panels combined with energy storage systems (ESS) are no longer a luxury, but a necessity.
How Earthquakes Affect the Grid
During an earthquake, even a moderate one:
Utility infrastructure is vulnerable. Power lines, substations, and transformers can be damaged, leaving neighborhoods in the dark.
Gas pipelines pose safety risks. This makes electric cooking and heating a safer and more reliable option during emergencies.
Restoration can take days. Depending on the severity, PG&E crews may need hours — even weeks — to restore service to all customers.
For homeowners, that means no lights, no internet, no heating, and no way to safely store food unless they have a backup system.
Why Energy Storage Systems (ESS) Matter
When paired with solar panels, battery storage systems like the Tesla Powerwall 3, Enphase IQ, or FranklinWH aPower give families independence from the grid.
From an engineering perspective, here’s what these systems can provide after an earthquake:
2+ Weeks of Critical Power: A well-sized battery can keep essential loads running — refrigeration, lighting, phone charging, internet routers, and medical equipment — for up to two weeks when managed carefully.
Safe Cooking & Heating: Electric induction cooktops, microwaves, or small space heaters can run off stored solar power, eliminating reliance on gas.
Automatic Isolation from the Grid: Modern ESS units include rapid shutoff and islanding capability, which means when the grid goes down, your home seamlessly switches to backup power.
Recharge Daily with Solar: Unlike a gas generator that needs constant refueling, a solar + battery system recharges every morning — ensuring sustainability for as long as the grid is down.
Real-World Resilience for Bay Area Families
Living in the Bay Area means preparing for the unexpected. With earthquakes, wildfires, and storms becoming more common, resilience isn’t optional — it’s essential.
Families who invest in solar + battery systems are not just saving on monthly utility bills; they are also investing in:
Peace of mind during natural disasters
Energy independence from PG&E’s outages and rate hikes
A cleaner, safer alternative to gas generators
Final Thoughts
The Berkeley/Pinole earthquake is a reminder that the grid is fragile, but your home doesn’t have to be. With solar panels and a properly designed energy storage system, you can keep life moving — cooking meals, heating your home, and staying connected — even when the lights go out across the city.
At Ally Electric and Solar, we specialize in designing and installing solar + battery systems that protect families during outages. If you’d like to learn how to make your home more resilient against earthquakes and other emergencies, contact us today for a free consultation.
9/18/25
How Does the NEM 3.0 Application Work?
When you apply for solar or add a battery in PG&E’s territory, your contractor (like Ally Electric and Solar Inc.) files an Interconnection Application. This is how it works:
Submit Interconnection Application
System details (panels, inverters, batteries) are entered into PG&E’s portal.
Required documents: site plan, single-line diagram, spec sheets.
PG&E Review
PG&E checks that your system complies with Rule 21 interconnection standards.
They confirm system size, safety ratings, and that your main panel can handle the system.
Permission to Operate (PTO)
Once approved and inspected, PG&E issues PTO.
This is the official green light for you to run your solar + storage system and start receiving NEM 3.0 credits.
What Does This Mean for Homeowners?
Under NEM 3.0:
Payback is longer without storage → Solar alone saves less because export credits are lower.
Solar + Battery is the new standard → A battery allows you to store daytime power and use it at night, making your system pay off faster.
Energy Security → Batteries provide backup power during PG&E outages.
How Ally Electric and Solar Inc. Can Help
At Ally Electric and Solar Inc. (Richmond, CA – CSLB #806465), we’ve guided hundreds of Bay Area families through the PG&E application process. We handle:
Preparing and submitting your NEM 3.0 interconnection application.
Designing systems that maximize self-consumption under new rules.
Installing trusted batteries like Tesla Powerwall, Enphase IQ, FranklinWH.
Panel upgrades and permitting for seamless integration.
Take Action Now
The sooner you apply, the sooner you can lock in savings and protect your home from rising PG&E rates.
Contact us today to get started with your NEM 3.0 solar + storage consultation.
510-559-7700
info@allyelectricandsolar.com
www.allyelectricandsolar.com
CSLB License #806465
FQAs
1. If I sell excess energy to PG&E, will PG&E charge me for it?
No — PG&E does not charge you for exporting your excess solar energy. Instead, under NEM 3.0, they give you export credits on your bill. The difference is that these credits are now much lower (around 5–8¢ per kWh) compared to the near-retail credits homeowners received under NEM 2.0. That’s why using your own solar energy or storing it in a battery provides greater savings than sending it back to the grid.
2. Will I still get the 30% Federal Solar Tax Credit under NEM 3.0?
Yes. The 30% Federal Investment Tax Credit (ITC) is completely separate from NEM policies. It applies to both solar and battery systems installed through the end of 2025.
3. Is it still worth going solar under NEM 3.0?
Yes — but the strategy has changed. Solar alone saves less than it used to because export credits are lower. Pairing solar with a battery system allows you to store your extra energy and use it during expensive peak hours, which dramatically improves your savings.
4. Can I keep my old NEM 2.0 plan if I already have solar?
Yes. If your system was approved under NEM 2.0, you are grandfathered into that program for 20 years from your Permission to Operate (PTO) date. However, adding new solar capacity may trigger a new NEM 3.0 review. Adding only a battery (without increasing solar size) usually does not change your NEM 2.0 status.
5. How long does the NEM 3.0 application take?
After submitting your application and documents, PG&E typically takes 2–4 weeks to review. Once the city inspection is complete and passes, PG&E issues your Permission to Operate (PTO).
6. Can I charge my battery from the grid under NEM 3.0?
Yes, depending on the configuration. Systems like Tesla Powerwall and Enphase IQ Battery can be set to allow or prevent grid charging. Most homeowners in PG&E territory choose “solar-only charging” to comply with NEM requirements and maximize savings.
7. What happens if I use more electricity than my solar produces?
You’ll still receive energy from PG&E, and you’ll be billed at normal rates for that extra usage. Your solar + battery system helps reduce this by covering as much of your home’s load as possible.
Lower-Quality Equipment: The Shortcuts in Cheap EV Charger Installations
When it comes to EV charger installations, you might be tempted by lower prices, but often, they come with compromises that can cause more headaches down the road. Here’s what you need to know about some of the shortcuts that make cheap installs risky:
Cheap EV Chargers: Lower-priced chargers may lack important features like smart capabilities, safety certifications, or built-in protections. These chargers might not handle the power demands of modern EVs, or they may not last as long. Sure, the price is tempting, but you’re often trading reliability for a quick deal.
Inadequate Wiring: Budget installers sometimes use cheaper wiring, like aluminum wire instead of copper. Aluminum may save a few bucks upfront, but it’s much more prone to corrosion and expansion when temperatures fluctuate. This can lead to loose connections, overheating, and a higher risk of fire hazards. Copper wire, while a bit pricier, is much more durable and reliable for high-power systems like EV chargers.
Substandard Circuit Breakers: The circuit breakers used in cheaper installs may not meet safety standards, which can increase the risk of electrical fires or a system failure. Quality breakers are there to protect your home and the vehicle you’re charging, so don’t skimp on this important part.
Low-Grade Mounting and Enclosures: Cheap installations may also cut corners with the mounting brackets or enclosures that hold your charger. These might be made from materials that wear down more quickly or degrade in the weather, causing long-term problems and potential safety issues.
Lack of Compliance with Standards: Some low-cost installations might use non-certified equipment that doesn’t meet local or national electrical codes. Not only does this increase the risk of a malfunction, but it could also void your warranty or make it harder to get insurance coverage. Plus, many cities require a permit and approval for EV charger installations, especially if it involves electrical work. Skipping these legal steps can cause issues later, including fines or delays, and it can even affect your insurance claims if something goes wrong.
Top Energy Saving Tips for a Greener, More Cost-Effective 2025
As we step into the new year, one of the best resolutions you can make is to focus on reducing your energy consumption. Not only will this help lower your utility bills, but it will also contribute to a more sustainable future for the planet. Whether you're looking to save a little money or reduce your carbon footprint, here are some simple energy-saving tips to kickstart your 2025.
1. Embrace Solar Power
One of the most impactful ways to save energy and money is by switching to solar power. Solar panels can help you harness the sun’s energy to power your home, reducing reliance on the grid and lowering your electricity bill. Plus, many areas offer incentives and rebates that make installing solar even more affordable. Investing in solar energy is a long-term solution for reducing your environmental impact while saving on energy costs.
2. Upgrade to Energy-Efficient Appliances
Older appliances tend to use more energy, so upgrading to energy-efficient models is a smart move. Look for appliances with the ENERGY STAR label, which indicates they meet strict energy efficiency standards. Replacing old refrigerators, washing machines, and air conditioners with energy-efficient ones will reduce your energy consumption and help save you money over time.
3. Seal Leaks and Insulate Your Home
Heat loss and air leaks can account for a significant portion of your energy bill, especially during the colder months. Check around windows, doors, and ducts for leaks and seal them with weather stripping or caulking. Adding insulation to your attic, walls, and floors will also help keep your home warm in winter and cool in summer, reducing the need for excessive heating or cooling.
4. Use Smart Thermostats
A smart thermostat allows you to set your home’s temperature based on your schedule, reducing the time your heating or cooling system runs unnecessarily. You can program it to lower the temperature when you're away and increase it before you come home, ensuring you're not wasting energy when you're not around. Many smart thermostats can also be controlled remotely via your smartphone, making it easier to manage your home's temperature efficiently.
5. Switch to LED Lighting
LED lights are far more energy-efficient than traditional incandescent bulbs. They use up to 80% less energy and last significantly longer. Consider switching all of your home’s lighting to LED bulbs to reduce your energy consumption and avoid frequent replacements. It’s a simple upgrade with a big impact on your energy bill.
6. Unplug Devices When Not in Use
Many electronics and appliances continue to draw power even when they’re turned off. This is known as "phantom energy" or "standby power." To avoid this, unplug devices like chargers, toasters, and coffee makers when you’re not using them. Alternatively, you can use power strips to make it easier to disconnect multiple devices at once.
7. Wash Clothes in Cold Water
Washing clothes in hot water uses a significant amount of energy, so switching to cold water can help reduce your energy bill. Cold-water detergents are just as effective as hot water ones, so there’s no need to sacrifice cleanliness. Additionally, whenever possible, try air-drying your clothes instead of using the dryer.
8. Limit Use of Space Heaters and Air Conditioners
Space heaters and air conditioners are often energy-intensive. Instead, try to adjust the temperature in your home to a comfortable level without relying on these devices. In the winter, layer up with warm clothing and use blankets to stay cozy, and in the summer, consider using fans instead of constantly running the AC.
9. Use Power-Saving Mode on Electronics
Many modern electronics come with power-saving modes or settings that automatically reduce energy consumption when the device is idle. Be sure to enable these features on your TV, computer, or gaming consoles to minimize energy use when they are not in active use.
10. Consider Solar-Powered Gadgets
If you're interested in even more ways to reduce your energy consumption, consider using solar-powered devices such as garden lights, chargers, or even outdoor appliances. These devices rely on the sun’s energy, allowing you to harness renewable energy without adding extra costs to your utility bill.
Final Thoughts
Saving energy doesn’t have to be complicated or expensive. With a few small changes and smart upgrades, you can reduce your energy consumption, lower your utility bills, and contribute to a more sustainable world. Start implementing these tips in 2025, and you'll see the benefits in both your wallet and the environment.
Your friends at Ally Electric and Solar are always here to help you find the best energy-saving solutions for your home. Interested in learning more about solar power or other energy-efficient upgrades? Reach out to us at 510-559-7700 and let's make 2025 your most energy-efficient year yet!
How Many Circuits Can a Single Powerwall 3 Backup? Exploring the Limits and Possibilities
"Wondering how many circuits a single Tesla Powerwall 3 can back up? The answer depends on your home's energy consumption and backup needs. With a capacity of 13.5 kWh and a continuous output of 11,500W, a Powerwall 3 can support several essential circuits, but the number varies based on the total power demand. Learn how to calculate your backup power needs and when to consider adding additional Powerwalls for larger systems."
When considering a home energy storage solution like the Tesla Powerwall 3, one of the most common questions homeowners have is how many circuits it can back up. After all, the goal of investing in solar power and storage is to keep essential appliances running during power outages or when energy prices surge. But how do you determine the number of circuits that can be supported by a single Powerwall 3?
In this blog post, we’ll explore the key factors that affect how many circuits you can back up with the Powerwall 3, and how to calculate your home’s energy backup needs.
TESLA Powerwall 3 installation
The Powerwall 3: Key Features at a Glance
To understand how many circuits a Powerwall 3 can support, it’s important to first review its core specifications:
Energy Capacity: 13.5 kWh (13,500 watt-hours)
Continuous Output: 11,500W
Peak Output: Up to 22,000W for short bursts (1 second)
Load Starting Capability: Can handle up to 150 amps for brief periods (1 second)
The energy capacity (13.5 kWh) tells you how much energy the Powerwall 3 can store and provide, while the continuous output (11,500W) indicates how much power it can supply to your home at any given moment. The load starting capability is particularly important for appliances like air conditioners or refrigerators, which require a higher surge of energy when they start up.
How Does Powerwall 3 Backup Work?
To figure out how many circuits can be backed up, we need to consider several factors:
Energy Consumption of Your Home’s Circuits
The total number of circuits a Powerwall 3 can back up depends on the energy consumption of those circuits. A typical home might have a range of circuits, including:Essential circuits: These might include lights, refrigerators, HVAC systems, and medical equipment.
Non-essential circuits: Things like TVs, small appliances, and other non-critical devices.
Each circuit will consume a certain amount of power, usually measured in watts (W) or kilowatts (kW). For example:
A refrigerator might consume 100-200 watts on average, but it will require a surge of power when starting up.
An air conditioning unit could consume around 1,000 watts or more depending on the size.
Total Power Demand and Powerwall 3’s Limits
The Powerwall 3 can provide a continuous output of up to 11,500W. This means that the total power demand from the circuits you wish to back up should not exceed this limit at any given moment. For example:If you want to back up a refrigerator (200W), lights (100W), and a few small appliances (500W), the total continuous demand would be around 800W, well within the Powerwall 3’s capacity.
However, if you're trying to back up high-demand circuits like an air conditioner or large electric oven, you’ll hit the limit much sooner.
Energy Duration
Another key factor is the duration you want to back up your circuits. While a Powerwall 3 can handle significant loads, it only has a total energy storage capacity of 13.5 kWh. For instance:If your total load is 1,000 watts (1 kW), the Powerwall could theoretically back up these circuits for 13.5 hours (13.5 kWh / 1 kW = 13.5 hours).
If your total load is 3,000 watts (3 kW), the backup duration would drop to 4.5 hours.
Therefore, the more circuits you wish to back up, the quicker the energy will be consumed. This is why multiple Powerwalls might be required for homes with high energy demand or for longer backup durations.
How Many Circuits Can Be Backed Up with One Powerwall 3?
To provide a practical answer, let’s break it down:
Basic Setup (Low Power Load): If you’re only backing up a few basic circuits like lights, a refrigerator, and a couple of small appliances, a single Powerwall 3 may be sufficient. For example, with a load of 800 watts, it could run for up to 16 hours (13.5 kWh / 800W).
Moderate Power Load: For more demanding circuits—like a refrigerator, a well-pump, and HVAC system—a Powerwall 3 might be able to support these for a few hours, but it would depend on the exact load. For instance, if your backup load is 3,000 watts, expect around 4.5 hours of backup time.
High Power Load: If you’re trying to back up high-draw circuits like an electric oven, large air conditioning units, or electric heaters, the number of circuits you can back up will be very limited by the Powerwall’s 11,500W continuous output.
In short, a Powerwall 3 can support 1 to 3 typical home circuits, depending on your household’s power usage. But the more circuits you want to back up, the more critical it is to calculate the total power demand to ensure that the backup system is adequate for your needs.
When Do You Need More Than One Powerwall?
If your home’s energy needs exceed the capabilities of a single Powerwall, you can add additional Powerwalls to expand your backup capacity. Tesla allows you to install up to 10 Powerwalls in a single home system, which can cover even the highest power demand for long periods.
For larger homes or those with more demanding backup needs, installing multiple Powerwalls will increase both the total energy storage (kWh) and the number of circuits you can back up. Tesla’s advanced energy management system also ensures that the system will seamlessly switch between grid and battery power as needed, without disruption.
Conclusion
The number of circuits a single Powerwall 3 can back up depends primarily on the total power demand of your home’s circuits and how long you want to maintain power. While the Powerwall 3’s 11,500W continuous output and 13.5 kWh storage capacity are powerful, they may not be enough for large homes with high energy needs. For most average homes, however, a Powerwall 3 will easily back up a few key circuits for several hours.
If you need more coverage, you can always expand your system with additional Powerwalls. The ideal solution depends on your unique energy usage and backup priorities.