How is a generator's size determined using a generator sizing guide?

A generator's size is determined by a load calculation. This process adds the total Running Watts of all essential appliances and then adds the single largest Starting Watt (Surge) requirement (usually the AC unit) to find the total Kilowatt (kW) need. GenStar provides this service free of charge in Central Florida.

How does the Generac generator sizing guide use load shedding?

The Generac generator sizing guide uses Smart Management Modules (SMMs) to perform load shedding. This means a smaller generator can cover more circuits by prioritizing power and temporarily turning off (shedding) non-critical appliances when a high-surge item, like a central AC, starts. This makes the system more cost-efficient.

What is the key sizing feature of a KOHLER generator sizing guide?

The key sizing feature for a KOHLER generator is its robust PowerBoost™ technology. This ensures superior motor-starting capability and provides fast, clean, and reliable power, which is ideal for sensitive electronics and multiple large motor loads common in Central Florida homes.

How does the Briggs & Stratton generator sizing guide handle power management?

Briggs & Stratton uses the Symphony® II Power Management System. This intelligent system manages high-wattage appliances by prioritizing power to essential circuits, which allows for a smaller, more affordable generator to effectively cover the home's most important backup power needs.

What size generator do I need for my business in Sanford, FL?

The size depends on the business's critical load, including servers, POS systems, and essential lighting. Commercial generator load calculation is complex and requires a professional audit of Tier 1 (critical) systems. GenStar specializes in providing custom commercial solutions for Generac and Tradewinds systems.

How to Choose the Right Size Generator for Your Home or Business (Load Calculations)

Never run out of power again! Choosing the correct generator size ensures your home or business stays fully powered during outages. If the generator is too small, it won’t power your essential appliances. If it’s too large, you pay more for power you don’t use.

The best way to get it right is by using a precise generator sizing guide and performing proper load calculations.

GenStar Generator Services, your trusted electricity partner in Sanford, FL, specializes in correctly sizing and installing systems from top brands like Generac, KOHLER, and Briggs & Stratton. We ensure your system is safe, efficient, and ready when you need it.

Generator Sizing Guide: What It Is and Why It’s Important

Selecting the right generator is more than picking a brand or fuel type. The size of your generator determines how much of your home or business you can power safely during outages. Using a generator that is too small can lead to overloaded circuits, while a unit that is too large may be an unnecessary investment.

Central Florida’s frequent storms and unpredictable power outages make generator sizing critical. A standby generator sizing guide helps you calculate your total electrical load, ensuring essential appliances, HVAC systems, and business operations continue seamlessly.

Here’s what you need to consider:

Essential vs. Whole-Home Coverage: Do you want to power only critical circuits, or the entire home or office?
Startup Loads: Appliances like air conditioners or refrigerators require more power at startup.
Fuel Source and Efficiency: Natural gas, propane, or diesel options affect both sizing and cost.

Following a proper generator sizing guide prevents underpowered systems and keeps your property safe during Florida storms.

How to Determine What Size Generator You Need

Installing a standby generator requires more than just picking a brand. The first, and most important, step is determining the correct size in Kilowatts (kW). This process, known as a whole-house generator sizing guide or load calculation, determines the total amount of power (electricity) your home or business needs to operate during an outage.

Why Load Calculation is Key to Sizing Your Generator

A precise load calculation prevents two costly mistakes:

Buying too small: If your generator cannot handle the starting power (surge power) and running power of your appliances (especially AC units and well pumps), it will overload and shut down.
Buying too large: Oversizing a generator increases the purchase price, installation cost, and fuel expenses. Proper sizing saves you money.

Our process uses the most accurate methods to calculate the necessary power, ensuring your system from Generac, KOHLER, or Briggs & Stratton is perfectly matched to your needs.

Power Needs: Homeowners vs. Business Owners

Audience	Typical Power Priorities	Sizing Focus
Homeowners & Retirees	Air Conditioning, Refrigerator, Lights, Medical Equipment (e.g., CPAP), Well Pump.	Standby generator sizing guide for essential and comfort circuits.
Business Owners	Security Systems, Critical IT/Servers, HVAC, Lighting, Refrigeration (Restaurants).	Commercial generator load calculation for continuous power demands.
Contractors & Builders	Ensuring correct sizing for new construction and upgrades to meet current codes and client expectations.	Whole home generator sizing guide for modern, energy-efficient homes.

The GenStar Advantage: We use the same detailed calculations required by utility companies and manufacturers to ensure your installation is fully certified and warrantied.

The Load Calculation Process Explained

The core of any generator sizing guide is the load calculation, which involves two main steps: identifying power requirements and determining the necessary transfer switch size. Every appliance and system in your home or business draws a specific number of watts, both for starting up and for continuous operation.

Here’s how professionals calculate it:

1. Identify Running Watts vs. Starting Watts

Every appliance has two power requirements measured in Watts:

Running Watts: The continuous power needed to keep an item running (e.g., a fridge keeping food cold).
Starting Watts (Surge): The extra, short burst of power needed for items with motors (like AC units or washers) to start up. This surge can be 2 to 3 times the running watts.

Appliance	Running Watts (Approx.)	Starting Watts (Approx.)
5-Ton Central AC Unit	5,000 W	15,000 – 18,000 W
Refrigerator/Freezer	700 W	2,200 W
Furnace Fan (1/2 HP)	600 W	1,800 W
Sump Pump	800 W	2,000 W

The Power Management Solution (Transfer Switch)

For a whole-home system, the generator connects through an Automatic Transfer Switch (ATS). This switch allows you to manage the power flow:

Essential Circuits: A smaller generator (e.g., 10-14kW) can power only your most essential circuits (lights, fridge, one AC unit).
Managed Whole House: A larger generator (e.g., 20-26kW) often uses load shedding technology. This means the generator powers the entire house, but the system automatically turns off non-critical, high-draw items (like an oven or second AC unit) to prevent overload when the main AC starts. This allows you to use a smaller, more cost-efficient generator.

For Central Florida homes, especially those with powerful AC units, this load management system is key. It lets a 22kW Briggs & Stratton generator, for example, effectively power a much larger home’s critical needs.

How Do I Determine What Size Generator I Need for My Florida Property?

A generator sizing guide helps you determine the exact amount of power your property needs during an outage. The goal is simple: make sure your generator can handle the electrical load of your home or business without overloading or underperforming.

When a generator is too small, it can struggle under heavy demand, tripping circuits, or shutting down critical systems. When it’s too large, it wastes energy, burns more fuel, and increases installation costs. The right size ensures safe operation, fuel efficiency, and long-term reliability.

For Florida homes and businesses that face frequent storm activity, proper sizing is the first step toward guaranteed uptime and peace of mind.

Determining your generator size begins with calculating your total wattage requirements.

List Appliances and Equipment: Walk through your home and list every appliance you must run during an outage. Common items include: Lights, Refrigerator, Garage Door Opener, Furnace/AC, Wi-Fi router, TV/Computer, Well Pump (if applicable).
Check Nameplate Ratings: Each appliance has a running wattage and startup wattage on its label.
Sum Running Wattages: Total all running wattages for continuous power needs.
Add Startup Wattage: Include peak startup wattages for heavy-load appliances.
Include Growth Margin: Add 10–20% extra capacity for future electrical needs or unexpected loads.

For example, a small home might need a 10–14 kW generator, while a mid-size business with refrigeration or IT systems may need 30–200 kW or more.

A professional load assessment, like those provided by GenStar’s certified installers, ensures your system matches your property’s exact electrical profile.

Why Correct Generator Sizing Matters:

Prevents system overload and damage
Ensures automatic startup during outages
Extends generator lifespan
Improves fuel efficiency and reliability
Meets Florida building and electrical codes

Pro Tip: For most Florida homes, a 22kW Generac or KOHLER standby generator provides full-home coverage.

Step 1: Calculate Your Total Power Needs

Before you select a generator, start with load calculation and an assessment of how much electricity your property needs to operate critical systems.

Residential Load Calculation Example

List essential items and their wattage:

Refrigerator – 800W
Air Conditioner (3-Ton) – 4,000W
Lights & Electronics – 1,500W
Well Pump – 1,000W
Sump Pump – 1,200W

Total Estimated Load: ~8,500W or 8.5 kW
In this case, a 10–12 kW generator would be ideal for whole-home coverage.

Commercial Load Calculation Example

For businesses, include:

HVAC Systems
Security Lighting
POS & Networking Equipment
Refrigeration or Machinery Loads

Most small-to-medium Florida businesses typically require 20–50 kW, depending on square footage and power-critical systems.

Pro Tip: GenStar offers free on-site energy load calculations to precisely measure your total wattage requirements.

Step 2: Choose Between Partial or Whole-Building Coverage

Partial Coverage (Essential Loads Only):
Power select circuits (lighting, refrigerator, sump pump, Wi-Fi). Great for budget-friendly backup.
Whole-Building Coverage:
Powers your entire home or business, including HVAC, security, and automation systems.

Our licensed installers in Sanford, FL, can configure automatic transfer switches (ATS) to match your backup goals, ensuring seamless, hands-free operation when the grid goes down.

Step 3: Select the Right Fuel Type

Different fuel sources impact performance, cost, and availability — especially during Florida’s hurricane season.

Fuel Type	Benefits	Considerations
Natural Gas	Unlimited supply, clean burning	Requires a gas line connection
Propane (LP)	Long shelf life, low maintenance	Needs an on-site tank
Diesel	High torque output	Requires regular fuel rotation

GenStar’s technicians are factory-certified to install and service Generac, Kohler, Briggs & Stratton, and Tradewinds generators, ensuring your system is perfectly matched to your local infrastructure and energy usage.

Step 4: Use a Generator Sizing Guide (and Expert Help)

A professional generator sizing guide isn’t just a calculator; it’s an engineering-based assessment that considers your starting loads, surge demands, voltage drops, and safety margins.

At GenStar, our technicians use advanced load software to determine:

Peak vs. average wattage needs
Future capacity planning for home additions or equipment
NEC-compliant wiring and breaker sizing

You’ll receive a custom load report and generator recommendation that fits your property and budget perfectly.

Standby Generator Sizing Guide for Homeowners

When the power goes out, every home has different priorities. Some homeowners want to keep only essentials running; others want full comfort without compromise.

Essentials-Only Backup (7–12 kW): Powers key circuits like the refrigerator, lights, and outlets.
Partial Home Coverage (13–20 kW): Keeps HVAC, water heater, and additional circuits operational.
Full-Home Systems (22–48 kW): Seamless operation for your entire home, including central air, appliances, and luxury amenities.

A whole-home generator sizing guide like this helps match the generator output to your home’s energy needs, ensuring that every system runs smoothly during Florida’s unpredictable storms.

What Size Generator Do I Need for My Business?

Commercial properties demand more complex calculations. Office buildings, restaurants, medical facilities, and industrial sites all have unique electrical loads.

To size a business generator accurately:

Identify mission-critical systems, servers, refrigeration, lighting, and HVAC.
Consider peak usage hours and seasonal variations.
Calculate total kW demand, then apply a safety factor for future equipment.

Restaurants may require 25–50 kW, while data centers or warehouses might exceed 100 kW. The right generator ensures your business never skips a beat, even when the grid goes down.

GenStar provides detailed commercial load assessments across Central Florida, ensuring compliance, uptime, and energy efficiency for every installation.

Choosing the Right Generator Brand and System Type

Once you have your power requirement (kW), the final step in the generator sizing guide is selecting the right brand and system features. GenStar is a factory-authorized dealer for the most trusted names in backup power.

Below are brand-specific sizing guides from Generac, Briggs & Stratton, and Kohler to help you match your home’s energy demands to the right system.

Generac Generator Sizing Guide

Generac is the #1 name in standby generators for Florida homes and for good reason. Their systems automatically start within seconds of an outage, keeping your lights, air conditioning, and appliances running smoothly.

Home Size & Load Calculation: Generac recommends adding up your running wattage and peak startup wattage to calculate your kW requirement.
Smart Management Modules: These allow you to prioritize circuits (like HVAC or refrigeration) so you can use a smaller, more efficient generator without sacrificing comfort.

Typical Generac Power Ranges:

Coverage Level	Generator Size	Key Features
Essential Circuits	7.5–11 kW	Keeps key appliances and lighting on
Partial Home	13–18 kW	Powers HVAC, refrigerator, and electronics
Whole Home	22–26 kW	Handles heavy loads including pool systems and dual ACs

Typical Residential Sizes

Home Size	Recommended Generac Model	kW Range
Under 2,000 sq. ft.	7.5–11 kW	10–12 kW
2,000–3,500 sq. ft.	13–18 kW	18–22 kW
Over 3,500 sq. ft.	22–26 kW	24–26 kW

Commercial Sizes

Home Size	Recommended Generac Model	kW Range
Under 2,000 sq. ft.	7.5–11 kW	10–12 kW
2,000–3,500 sq. ft.	13–18 kW	18–22 kW
Over 3,500 sq. ft.	22–26 kW	24–26 kW

Generac’s exclusive features:

True Power™ technology for clean, consistent electricity
Automatic transfer switches for seamless transitions
Remote monitoring via the Mobile Link™ app

Pro Tip: GenStar’s certified technicians provide complete Generac installation, maintenance, and warranty service in Sanford and throughout Central Florida.

Briggs & Stratton Generator Sizing Guide

Briggs & Stratton focuses on durability and performance, with generators tailored for both small homes and large estates. Their Power Management System optimizes energy flow automatically, ensuring efficient performance even during long outages.

Suggested Briggs & Stratton Generator Sizes:

Home Type	Generator Size	Key Features
Small Homes / Cabins	10–12 kW	Powers essentials and select circuits
Medium Homes	17–20 kW	Manages larger appliances and central air systems
Large Homes / Estates	25–30 kW	Delivers full-home coverage with automatic transfer switch

Pro Tip: Their Amplify™ Power Management technology prioritizes high-demand appliances, preventing overload and extending runtime.

KOHLER Generator Sizing Guide

KOHLER’s generators are known for exceptional voltage stability and premium build quality. For homeowners and businesses who prioritize premium reliability and quiet performance, KOHLER generators deliver exceptional durability and industry-leading power quality.

Precision Power Mapping: KOHLER focuses on balancing startup surges to maintain stable voltage, especially for HVAC or medical-grade systems.
KOHLER PowerSync Technology: Allows multiple units to sync together, giving scalable power solutions for businesses.

What sets KOHLER apart:

100% corrosion-proof enclosures built for Florida’s humidity
Heavy-duty engines are tested for thousands of hours of continuous use
Fast, automatic response times with precision voltage regulation

Recommended Kohler Generator Sizes for Typical Florida Homes

Home Type	Generator Size	Key Features
Condo / Small Home (1,000–1,500 sq. ft.)	8–10 kW	Covers lights, refrigerator, and small AC units
Mid-Sized Home (1,500–2,500 sq. ft.)	14–20 kW	Powers HVAC, security system, and kitchen appliances
Large Home (2,500–4,000+ sq. ft.)	24–30 kW	Whole-home coverage supports pool pump and dual ACs

Pro Tip: KOHLER recommends professional sizing through a certified dealer like GenStar. Our technicians calculate precise load needs and match you with the most efficient KOHLER generator model.

Generator Brand Comparison: Generac vs. Kohler vs. Briggs & Stratton

For Homes (1,000 – 3,000 sq ft):
Generac 13–18 kW or Kohler 14–20 kW models are ideal for most Florida single-family homes, providing full comfort during outages.

For Small Businesses (3,000 – 5,000 sq ft):
Briggs & Stratton 20–25 kW or Kohler 24 kW units support HVAC, POS systems, and security networks without interruptions.

For Commercial Buildings (5,000 + sq ft):
Kohler 30 kW or Briggs & Stratton 30 kW+ systems ensure stable performance for multi-unit buildings, offices, or retail spaces.

Breakdown by Use Case

For Homes (1,000 – 3,000 sq ft):
Generac 13–18 kW or Kohler 14–20 kW models are ideal for most Florida single-family homes, providing full comfort during outages.

For Small Businesses (3,000 – 5,000 sq ft):
Briggs & Stratton 20–25 kW or Kohler 24 kW units support HVAC, POS systems, and security networks without interruptions.

For Commercial Buildings (5,000 + sq ft):
Kohler 30 kW or Briggs & Stratton 30 kW+ systems ensure stable performance for multi-unit buildings, offices, or retail spaces.

Common Mistakes in Generator Sizing (and How to Avoid Them)

25Choosing the wrong generator size is a costly mistake that can lead to power failures, equipment damage, or wasted energy. Here are the most common pitfalls and how to avoid them:

Underestimating Startup Power

Appliances like AC units and refrigerators draw extra “surge watts” when starting up. Undersized generators can trip breakers or shut down.
Fix: Include surge power in your load calculation or get a professional load test.

Overlooking Essential Circuits

Many forget about small but critical systems like sump pumps, Wi-Fi routers, or medical devices.
Fix: Make a complete list of everything that must stay on during an outage.

Oversizing the Generator

Too much capacity wastes fuel, costs more, and causes inefficient operation.
Fix: Aim for 70–80% usage of your generator’s capacity for optimal efficiency.

Ignoring Future Power Needs

Adding new appliances or an EV charger later may overload your system.
Fix: Add a 15–20% buffer for future expansion.

Relying on Online Calculators Alone

Online tools can’t factor in real-world electrical loads or Florida’s building codes.
Fix: Have a certified installer, like GenStar Generator Services, perform an on-site load evaluation.

Pro Tip: If you’re unsure whether your existing generator is properly sized, schedule a preventive generator maintenance with GenStar. Our technicians can simulate a full power outage to measure your generator’s response and verify that it can support your property’s true energy requirements.

Secure Your Power Plan Today!

The right generator size makes all the difference. From precise load calculations to expert installation, our team ensures every system is safe, efficient, and built to last.

The right generator size keeps your property safe, energy-efficient, and fully powered. With expert load analysis and professional installation from GenStar, you’ll never guess your power needs again.

Whether you’re looking for a Generac or Briggs & Stratton generator sizing guide, or a full commercial power solution, our local team ensures you get the right system the first time.

Ready to size your generator the right way? Schedule a free power load consultation with GenStar today, serving Sanford, Orlando, and all of Central Florida.