You’ve probably typed “solar panel calculator” into Google a dozen times and gotten wildly different answers. One website says 5 kW, another says 12 kW, and you’re left more confused than when you started.
Here’s some info that might help: the size of your solar system isn’t determined by your home’s square footage or what your neighbor installed. It comes down to how much electricity you actually use, how much sun hits your roof, and what you plan to do with your home in the next few years.
After installing solar systems throughout Los Angeles, Ventura, and Orange Counties since 2007, AWS Solar has helped many homeowners figure out exactly what they need. Not what sounds impressive. Not what some online calculator spits out. Just what makes sense for their bills and their goals.
Let’s walk through the real factors that determine your system size.
Your Electric Bill Tells the Whole Story
Most people start by asking about their roof size or how many panels fit up there. That’s backwards.
Start with your Southern California Edison bill (or whichever utility you use). Flip to the page showing your annual kilowatt-hour (kWh) usage. That number is the foundation of everything.
Homes we work with typically use anywhere from 400 to 1,200 kWh per month, depending on size, air conditioning habits, and how many people live there. That’s a huge range, which is why cookie-cutter recommendations rarely work.
If you’re using 700 kWh monthly (8,400 kWh annually), you’d need roughly a 6 kW system to cover that usage. Jump to 1,000 kWh per month? You’re looking at closer to 9 kW.
For those considering a solar roof installation in Los Angeles, understanding your baseline usage is where it all begins.
Southern California’s Solar Sweet Spot
Good news: you live in one of the best places in the country for solar production.
Systems here generate about 1,500 to 1,800 kWh per installed kilowatt each year. That means a 6 kW system produces roughly 9,000 to 10,800 kWh annually. Compare that to cloudier regions where production drops to 1,200 kWh per kW, and you’ll see why California homeowners can get away with smaller, more affordable systems.
Your exact production depends on:
- Roof orientation (south-facing is ideal, but east and west work fine)
- Shading from trees or nearby buildings
- Panel efficiency and system design
We always conduct a site evaluation to measure these factors rather than rely on estimates. Shading from one tree can drop your production by 20% if panels are placed poorly.
What Size System Do Most Homes Actually Need?
Let’s cut through the theory and look at real numbers. Based on current consumption patterns in our service areas, here’s what we typically see:
| Monthly Usage | Annual Usage | System Size Needed |
| 400-600 kWh | 4,800-7,200 kWh | 4-6 kW |
| 700-900 kWh | 8,400-10,800 kWh | 6-9 kW |
| 1,000-1,200 kWh | 12,000-14,400 kWh | 9-12 kW |
For context, the average system size we’ve quoted recently in Los Angeles hovers around 10 kW. That reflects homes with moderate to high usage, often including air conditioning, pools, or home offices.
Smaller, energy-efficient homes or condos might only need 4-5 kW. Larger family homes with multiple AC units and appliances running all day? Easily 10-12 kW.
Adding an Electric Vehicle Changes Everything
Planning to buy an EV or already charging one at home?
Daily charging adds about 300 to 500 kWh to your monthly usage. That translates to an extra 3 to 5 kW of solar capacity if you want to offset those charging costs.
Many homeowners underestimate this. They size their system based on current usage, then realize six months later that their new Tesla is pulling power they didn’t account for. We help coordinate solar panels and EV charging for homes so everything works together from day one.
If an EV is on your radar within the next few years, plan for it now. Adding more panels later is possible but often more expensive than doing it right the first time.
Why California’s Net Billing Rules Matter for Sizing
Here’s where things get a bit technical, but it directly affects how big your system should be.
California switched to Net Billing (NEM 3.0) in 2023, and it’s still the rule in 2026. Under this policy, the credits you earn for sending excess solar power back to the grid are about 75% lower than they used to be.
What does that mean for you?
Oversizing your system without battery storage doesn’t make much financial sense anymore. If you install a 15 kW system but only use 10 kW worth of energy, that extra production gets exported to the grid at a reduced rate. You won’t see the savings you expect.
Instead, we generally recommend:
- Sizing to match your annual consumption (100-150% if you’re adding electrification like heat pumps or EVs)
- Pairing your system with battery storage to capture daytime solar production for evening use
- Avoiding massive oversizing unless you have verified future needs
Battery storage has become a key piece of the puzzle. It lets you store excess daytime energy and use it at night when rates are higher. Under current policies, that’s often where the real savings come from.
Don’t Forget About Battery Storage Incentives
While the federal 30% tax credit for solar ended after December 31, 2025, California’s Self-Generation Incentive Program (SGIP) still offers rebates for battery storage.
Depending on your location and household income, you could receive:
- Up to $1,100 per kWh for battery storage in equity-eligible programs
- Additional pairing incentives for combining solar with batteries
These incentives can significantly reduce the upfront cost of adding storage, making it easier to maximize your solar investment. Since SGIP funding is limited and allocated on a first-come basis, it’s worth exploring sooner rather than later.
If you’re considering batteries, consult with a licensed contractor to determine eligibility and current funding availability.
Business Solar Sizing Works Differently
Residential solar is straightforward: match your annual usage, plan for future needs, done.
Commercial solar requires analyzing your business’s specific load profile. Do you run heavy machinery during the day? Operate mostly in the evening? Have seasonal demand spikes?
Businesses with high daytime energy use (think warehouses, retail stores, or offices) align perfectly with solar production. You’re using power when the sun is shining, which maximizes your savings without needing as much battery capacity.
On the flip side, restaurants or entertainment venues with evening-heavy operations might need larger battery systems to store daytime solar for nighttime use.
System sizes for businesses typically range from 20 kW to well over 100 kW, depending on square footage and operations. We always recommend a detailed energy audit before moving forward with commercial installations.
How We Help You Get the Right Size
Every home is different. Every electric bill is different. That’s why we don’t rely on online calculators or one-size-fits-all recommendations.
Here’s what a proper sizing consultation with AWS Solar looks like:
1. Review Your Utility Bills
We examine at least 12 months of usage to account for seasonal variations. Summer AC loads can be double your winter usage, so annual data matters.
2. Conduct a Site Assessment
We measure your roof’s dimensions, check for shading, and evaluate structural capacity. Not all roofs can handle every system size, and some have better solar access than others.
3. Discuss Your Future Plans
Are you adding an EV? Planning a home addition? Considering a pool? These factors influence your system size more than most people realize.
4. Model Your Production
Using site-specific data, we calculate how much energy your system will actually produce. We don’t guess. We model it based on your exact roof orientation, shading, and local weather patterns.
5. Present Your Options
We show you different system sizes, explain the tradeoffs, and let you decide what fits your budget and goals. Some homeowners want to offset 100% of their usage. Others are happy with 80% if it saves money upfront.
The goal is to give you enough information to make a confident decision, not to push you toward the most expensive option.
What Happens If You Size It Wrong?
Too small, and you’re still paying hefty electric bills every month. You’ll wonder why you bothered going solar in the first place.
Too large without storage, and you’re exporting power at low rates under NEM 3.0. You’ve spent more money than necessary for minimal additional benefit.
Getting it right means balancing your current usage, future plans, and budget. That’s where working with an experienced local contractor makes all the difference. We’ve sized numerous systems across Los Angeles, Ventura, and Orange Counties, and we’ve seen what works and what doesn’t.
Ready to Find Out What You Actually Need?
Forget the guesswork. Let’s look at your actual bills, evaluate your roof, and design a system that makes sense for your home and your budget.
AWS Solar has been serving Southern California since 2007, and all our work is handled by our in-house crews. No subcontractors. No surprises. Just reliable installations backed by nearly two decades of experience.
Whether you’re looking at solar panels alone or pairing them with battery storage and EV charging, we’ll help you figure out exactly what you need.
Contact AWS Solar today for a free consultation. We’ll review your energy usage, assess your property, and give you a clear recommendation based on real data, not sales tactics.
Frequently Asked Questions
How do I calculate what size solar system I need for my home?
Start with your annual kWh usage from your utility bills. Divide that number by the expected annual production per kW in your area (typically 1,500-1,800 kWh/kW in Southern California). That gives you a baseline system size. Factor in future needs like EV charging or home additions, and consider pairing with battery storage under current net billing rules.
What’s the average solar system size for homes in Los Angeles County?
Based on recent installations, the average residential system size in Los Angeles County is around 10 kW. However, actual needs vary widely based on usage, ranging from 4-6 kW for smaller or highly efficient homes to 12+ kW for larger homes with high electricity consumption or EV charging.
Do I need a bigger system if I charge an electric vehicle at home?
Yes. Home EV charging typically adds 300-500 kWh to your monthly electricity usage, requiring an additional 3-5 kW of solar capacity to offset those costs. If you plan to buy an EV soon, it’s usually more cost-effective to size your system accordingly from the start rather than adding panels later.
Is it worth oversizing my solar system in California?
Not without battery storage. Under California’s current Net Billing rules (NEM 3.0), excess energy sent back to the grid earns significantly reduced credits. Oversizing your system without storage means you’re paying for production you won’t fully benefit from. Most homeowners see better returns sizing to their actual consumption and adding batteries.
Are there still solar incentives available in California in 2026?
The federal 30% Residential Clean Energy Credit expired after December 31, 2025, so it no longer applies to new installations. However, California’s Self-Generation Incentive Program (SGIP) still offers rebates for battery storage, with equity-eligible programs providing up to $1,100 per kWh for storage and additional solar pairing incentives in qualifying categories.How long does it take for a solar system to pay for itself in Southern California?
Payback periods vary based on system size, electricity rates, usage patterns, and whether you include battery storage. With proper sizing and current electricity rates in SCE territory, many homeowners see payback in 6-10 years. A licensed contractor can provide a more accurate estimate based on your specific situation.