Home Generator Sizing Guide for California

Choosing the right size for your home generator is the most crucial step in ensuring you have reliable backup power. It’s all about making sure you have enough power (running watts) for everything you need to keep on, plus enough of a kick (starting watts) to handle the initial jolt from big appliances like your air conditioner. The goal is to perfectly match the generator's capacity to your home’s real needs, so you aren't overspending on a unit that's too powerful or risking damage with one that's too small.

Why Getting the Generator Size Right Is So Important in California

Living in California means being ready for the unexpected. We've all experienced Public Safety Power Shutoffs (PSPS) during wildfire season or watched the grid strain under a summer heatwave. In this environment, a generator isn't just a luxury; it's an essential tool for keeping your home safe and functional.

But just buying a generator isn't enough. Picking the right size is what truly makes a difference when the power goes out.

An undersized generator is a recipe for disaster. If you try to power more than it can handle, it will overload. That strain can damage the generator's engine and sensitive components, leaving you with a costly repair bill. Even worse, an overloaded generator produces unstable electricity that can easily fry the electronics in your computers, TVs, and modern appliances.

On the other hand, buying a generator that’s too big is simply a waste of money. You'll pay more upfront for the unit and installation, and it will burn through more fuel than necessary every time it runs. That inefficiency adds up, making your backup power solution far more expensive than it needs to be.

The Rush for Reliable Home Power

This isn't just happening in California; homeowners everywhere are seeking energy independence. As power grids face increasing strain from extreme weather and high demand, more people are investing in their own backup systems.

The global market for home standby generators was worth around USD 8.5 billion in 2024 and is expected to nearly double by 2034. You can read more about this growing market to see what's driving this trend. It’s clear that people are realizing that having control over their own power is a key part of modern home security.

The sweet spot is a generator powerful enough to run your essentials and a few comforts without struggling, but still efficient enough that you’re not wasting money on capacity you’ll never use.

We created this guide to simplify the process for California homeowners. We’ll walk you through how to figure out your true power needs—from keeping critical medical devices online to running the AC on a blistering day. Getting the size right from the start ensures your investment pays off with dependable power whenever you need it most.

Ready to find the perfect generator size for your home? The team at RC Generators and Electric specializes in helping homeowners in Los Angeles and Ventura County. Contact us today for a personalized consultation

Calculating Your Home's Real Power Needs

Figuring out exactly how much power your home needs is the most important step in choosing the right generator. Don’t worry about complex electrical jargon—think of this more like creating a simple power budget. It's all about deciding what you absolutely need to keep running versus what you can live without for a while.

The best way to start is by making a list. We’ll sort your appliances into three categories to make it easy.

• Essentials: These are your non-negotiables. Think refrigerator, freezer, sump pump, and any critical medical equipment. For many of us here in California, a well pump is also on this list. A few lights for safety are a must, too.

• Comforts: These are the items that make an outage much more comfortable. We're talking about your Wi-Fi router, television, computer, and maybe a fan or a small window AC unit to take the edge off the heat.

• High-Demand Items: Now we get to the power-hungry appliances. Your central air conditioner, electric clothes dryer, electric stove, or a large water heater fall into this category. Powering these big items requires a much larger—and more expensive—generator.

Once your list is sorted, it’s time to figure out how much power each item actually uses.

Finding Your Running and Starting Watts

Every appliance has two different power ratings you need to know: running watts and starting watts.

Running watts are what an appliance needs to run continuously. Starting watts (also called surge watts) are that extra jolt of power a device with a motor needs for a few seconds to start up. This is where most people get confused.

You can usually find these numbers on a sticker or data plate right on the appliance. If it's not there, the owner's manual is the next best place to look. Getting both numbers is critical, because that initial starting wattage is often what overloads a small generator.

This infographic gives a great visual of the power assessment process, starting with a look at your home's electrical panel.

As the image shows, a solid power assessment is the foundation for getting your generator size right the first time.

A Practical California Home Example

Let's walk through a real-world scenario. Imagine a family in Ventura County dealing with a summer power outage. They’ve decided they want to power their essentials plus a few key comforts.

Here’s how they’d figure it out:

• Step 1: Add up the running watts. They list everything they want to run at the same time and add up the running wattage.

  • Refrigerator: 700 watts

  • Sump Pump: 1,050 watts

  • A few LED Lights: 100 watts

  • Wi-Fi Router & Modem: 20 watts

  • Television: 150 watts

  • Total Running Watts: 2,020

• Step 2: Find the highest starting watts. Next, they look at all their motor-driven appliances and find the single highest starting wattage. Their refrigerator needs 2,100 watts to start, and the sump pump needs 2,150. Since it's very unlikely both will start at the exact same moment, they only need to account for the biggest one.

  • Highest Starting Watts: 2,150 (from the sump pump)

• Step 3: Do the final math. Now, they add the total running watts to that single highest starting number.

  • 2,020 (Running) + 2,150 (Starting) = 4,170 Total Watts

This family needs a generator that can provide at least 4,170 watts to handle their specific needs without being overloaded.

Key Takeaway: The most common mistake is only adding up the running watts. You must account for the highest starting wattage in your calculation to prevent your generator from shutting down every time a large appliance kicks on.

To help you get started, here’s a quick reference chart with wattage estimates for common household items. Keep in mind these are just averages—always check your specific appliance for the most accurate numbers.

Common Household Appliance Wattage Cheat Sheet

This table should give you a solid starting point for your own calculation. For a deeper dive into the numbers, you can explore the details on this comprehensive generator sizing page.

Calculating your home's power needs takes a little effort, but it’s the only way to be sure you’re investing in a system that will actually work when you need it. If you're feeling unsure about your numbers or just want a professional to handle it, our licensed electricians are here to help. Contact RC Generators and Electric for an expert assessment in the Los Angeles and Ventura County areas.

Decoding Generator Wattage Ratings

Once you have a list of your home’s power needs, it's time to look at generators. You’ll see a big number advertised, like 9,000 watts, and it’s tempting to think that’s how much power you’ll get all the time.

The reality is a little different. Understanding what those numbers really mean is key to choosing a generator that won't let you down.

Running Watts vs. Starting Watts

The two most important figures are running watts and starting watts. The easiest way to think about them is like a long-distance runner versus a sprinter.

• Running Watts (or Rated Watts): This is your long-distance runner. It's the continuous, steady power the generator can produce for hours on end. This number is the true measure of a generator's sustainable power.

• Starting Watts (or Surge Watts): This is your sprinter. It’s that short, powerful burst of extra energy needed to get motors spinning in appliances like your refrigerator or AC unit. This surge capacity only lasts for a few seconds and is always higher than the running wattage.

So, that flashy 9,000-watt generator might only provide 7,500 running watts. The bigger number is great for marketing, but the running watts tell you what it can actually handle for the long haul.

The 20% Buffer Rule: An Essential Safety Margin

After you’ve matched your total required watts to a generator’s running watts, there’s one last important step: building in a safety buffer. A good rule of thumb is to pick a generator with at least 20% more capacity than your calculation.

For example, if you figured out you need 8,000 watts, you should look for a generator that can deliver at least 9,600 running watts.

This buffer isn't about overspending; it's about protecting your investment. Pushing a generator to its maximum capacity puts constant strain on the engine. That leads to more wear and tear, higher fuel consumption, and a shorter lifespan.

Adding that extra cushion ensures the generator runs efficiently without being overworked. It also gives you the flexibility to plug in an extra lamp or charge a phone without risking an overload. You can learn more about how all the parts work together by reading our guide on how a home generator works.

Choosing the right size is one of the most important decisions you'll make for safety and performance. Most California homeowners find their needs fall somewhere between the 5kW to 20kW range. A typical household looking to power major appliances will often land on a 10kW to 15kW unit for comfort and security.

Not sure if you’ve calculated the right buffer? The experts at RC Generators and Electric can review your numbers and give you a professional recommendation. Get in touch with us for a free consultation.

Whole House vs. Essential Circuits Power Strategies

Once you’ve figured out your home’s wattage needs, the next big question is a strategic one: what, exactly, do you need to power when the grid goes down? This decision is the biggest factor in determining the right generator for your home. For most California homeowners, it comes down to two main approaches.

The first is the whole-house strategy. Think of this as the ultimate "set it and forget it" solution. A powerful standby generator is installed to seamlessly take over your entire home's electrical system. When an outage hits, the system kicks in automatically. Life continues as normal. The central air keeps running, you can still do laundry, and the home office stays online without a single hiccup.

This approach offers total convenience and peace of mind, which is especially valuable during long outages or for anyone who relies on consistent power, like those running a business from home

The Essential Circuits Approach

The second strategy is what we call the essential circuits method. This is a more targeted—and budget-friendly—way to handle power outages. Instead of hooking up the entire house, a smaller generator is connected to a sub-panel that only powers pre-selected, critical circuits.

You get to decide what’s most important. Typically, this includes things like:

• Refrigerator and freezer

• A few lights in key areas

• Essential medical equipment

• The furnace fan for heat

During an outage, only those specific circuits get power. You won't be running the central AC or the dishwasher, but your food will stay cold and you'll have light where you need it. It’s all about covering the core needs for safety and basic comfort.

Comparing the Two Strategies

Choosing between these two options comes down to balancing convenience against cost. A whole-house system is a major upgrade. It requires a larger, more expensive generator and a more involved installation. It's the best choice for anyone who wants zero disruption to their daily life.

On the other hand, the essential circuits approach uses a smaller generator, which keeps the purchase price and ongoing fuel costs lower. The installation is usually simpler, too. The trade-off is that you have to be mindful of what you can and can't use during an outage. For many homeowners, this is the perfect middle ground between being prepared and being practical.

To make this decision a little easier, we’ve put together a quick comparison.

Whole House vs. Essential Circuits Which Is Right for You?

Ultimately, both paths lead to reliable backup power. The key is picking the one that aligns with your family’s needs.

The right choice depends entirely on your lifestyle, budget, and what "comfort" means to you during an outage. There's no single right answer, only the best answer for your specific situation in California.

This decision also ties directly into the type of generator you’ll choose. For a deeper dive, check out our comparison of portable vs. standby generators, as this often goes hand-in-hand with choosing your power strategy.

Whether you’re leaning toward complete home backup or just covering the basics, defining your goals is a critical part of the process. It ensures the generator you choose will perform exactly as you expect when you need it most.

California Installation and Safety Considerations

You’ve done the math and picked out the perfect generator. Now for the most important part: getting it installed safely and legally.

Here in California, with our strict building codes and safety regulations, this is not a weekend DIY project. Professional installation by a licensed electrician isn't just a recommendation—it's a requirement.

An expert ensures your entire system is compliant with local laws in areas like Los Angeles and Ventura County, saving you from major headaches with inspections or insurance claims. They handle the permits and ensure every connection is solid, protecting both your home and your investment.

Fuel, Placement, and Noise Rules

Before any work begins, there are a few key factors to think about that are specific to our state. Your installer will walk you through the options, but it helps to understand the basics.

First up is the fuel source. The two main choices are natural gas and liquid propane. Natural gas is convenient because it taps right into your existing utility line, meaning you never have to worry about refueling. If you don't have access to natural gas, propane is an excellent alternative, though it does require a large storage tank on your property.

Placement is another big consideration. California has specific fire codes that dictate how far a generator must be from windows, doors, vents, and property lines. These rules are in place to prevent dangerous exhaust fumes, especially carbon monoxide, from getting inside your home.

Local noise ordinances can also be a factor. Some communities have rules about how loud a generator can be and what hours it can operate. A professional installer will know the regulations in your city or county, ensuring your new generator doesn’t become a nuisance to the neighbors.

The All-Important Transfer Switch

The heart of any safe generator installation is the transfer switch. Think of this device as the brain of your backup power system. Its job is to safely disconnect your home from the utility grid before it connects to the generator.

Why is this so critical? It prevents a dangerous situation called "backfeeding," where electricity from your generator travels back into the utility lines. This could seriously injure or even kill line workers who are out there trying to restore power. A licensed electrician is required to install this crucial piece of equipment. Our guide on how to install a backup generator dives deeper into this essential process.

Getting these installation details right is the key to a reliable power solution you can count on.

If you're ready to take the next step, the licensed experts at RC Generators and Electric can manage every aspect of the process for you. Contact us today to schedule your professional installation in the Los Angeles and Ventura County areas.

You're Ready to Secure Your Home's Power

At this point, you have all the information you need to size your home generator with confidence. You know how to assess your appliances, calculate your total wattage (including that all-important surge!), and pick a strategy that makes sense for your family. Taking these steps is a huge move toward true energy independence.

This isn't just about numbers; it's about making sure your family stays safe and comfortable when the next power outage hits.

A thoughtful approach to sizing means you’ll invest in a system that’s just right—not too small and prone to failure, but not oversized and wasteful either. It’s the key to a smart, long-term solution.

If you're ready for the next step or just want a professional to double-check your calculations, our team is here for you. We can walk you through your specific needs and provide a clear, no-obligation quote for a professional, code-compliant installation right here in California.

Ready to get that peace of mind?

Get your free, no-obligation quote from RC Generators and Electric today!

A Few Common Sizing Questions We Hear All the Time

Even with a solid plan, a few questions always come up when homeowners are trying to size a new generator. Getting these details right can be the difference between a good guess and a perfect fit.

Let’s quickly cover a few of the things we get asked most often.

Can I Just Add Up the Wattage on All My Appliance Labels?

That's a great start, but it only gives you half the picture. The wattage on an appliance label is its running watts—the power it uses to operate continuously. What's missing is the starting watts.

Anything with a motor, like your refrigerator or air conditioner, needs a big jolt of extra power just to get going. This initial surge is often much higher than the running watts.

To get an accurate number, you need to:

1. Add up the running watts for everything you want to power at once.

2. Find the single appliance with the highest starting wattage.

3. Add that one starting wattage number to your total running watts.

This is the most common mistake people make. Forgetting about that initial power surge is the number one reason homeowners end up with a generator that’s too small.

Is a Bigger Generator Always Better?

Not necessarily. While we always recommend adding a 15-20% buffer for some extra room, going way too big is just wasteful. An oversized generator has to burn more fuel than necessary to produce the power you're actually using, which drives up your operating costs.

The goal isn’t to buy the biggest generator you can afford. It's to find the one that perfectly matches your calculated needs—plus a smart safety margin. This ensures your generator runs efficiently and lasts for years.

How Is Sizing Different for a Portable vs. a Standby Generator?

The math itself doesn't change, but your strategy will. A permanently installed standby generator is usually sized to power your whole house or, at a minimum, all of your essential circuits. Because it turns on automatically, the calculation is more comprehensive and includes a longer list of appliances.

A portable generator, on the other hand, is about picking and choosing. You're calculating the power needed for a handful of specific items you'll manually plug in with extension cords or a manual transfer switch. The load is much smaller and focused on just the absolute must-haves to get you through a temporary outage.

Feeling confident about your power needs? The licensed electricians at RC Generators and Electric can help you finalize your plan and ensure a safe, professional installation in Los Angeles and Ventura County.

Get Your Free Home Generator Quote Today!