To determine the size generator you need for your house, review your main appliances and total power requirements. Add up the running watts of each item, then leave room for surges and future upgrades. Using a generator sizing chart helps you determine the correct generator size to safely power your home during a power outage.
Grounded Electric’s licensed electricians, led by Robert “Bobby” Mulholland and Barret Abramow, help homeowners select the right generator capacity for safety, comfort, and long-term reliability.
Key Takeaways
- A generator sizing chart shows how to calculate total power requirements by comparing running and starting watts.
- Add up the total wattage, including 20 percent extra for surges, and select a generator that meets both current and future needs.
- Smaller homes often require 7.5–10 kW generators for essential services, while larger homes or businesses may need 20–60 kW for comprehensive coverage.
- Licensed electricians, such as Robert “Bobby” Mulholland and Barrett Abramow, ensure safe, code-compliant installations that meet NEC standards.
Generator Size Basics and Power Ratings
A generator sizing chart works best with real examples. Grounded Electric’s generator wattage chart shows both running and starting watts for household items.
Appliances with the highest starting watts require more surge power. Add all running watts together and include at least 20 percent extra for safety and growth.
How to Calculate the Right Generator Size
List every appliance you want to power and write down its running wattage. Add 20 percent for startup surges and future needs. You can also use a what size generator do I need for my house chart or calculator for an exact estimate.
The 20/20/20 rule – adding 20 percent for startup, 20 percent for expansion, and 20 percent for safety – helps keep your system balanced during high demand.
Smaller homes may need around 7.5 kW, while larger homes can require 15–20 kW to power all major systems.
Generator Size Chart
| Item | Running W | Starting W | Qty |
|---|
Tip: Enter quantities to include an item. You can edit names and watts or add custom lines.
How the calculator works
- We add all running watts and take the single highest starting watts.
- Base requirement = running total + highest starting.
- Safety margin adds extra headroom for real conditions.
- Use the result to compare portable and standby generators.
Values are typical references. Always check the nameplate on each appliance and follow local codes.
Generator Size Guide – Verified Bands for Homes and Light Commercial
Grounded Electric • Reference chartDisclaimer: Bands shown are guidelines from manufacturer literature and trade references. Actual sizing must follow a load calculation. Grounded Electric verifies loads on-site and can use load management or soft-start devices to right-size systems.
Residential and Commercial Generator Sizing
A home standby generator can restore emergency power within seconds after losing power. Commercial spaces often need 3-phase systems with higher surge tolerance. Grounded Electric designs both residential and commercial systems with safe transfer switches and code-approved wiring.
A workshop with multiple power tools may need 25 kW, while an office with lighting, HVAC, and computers might need up to 60 kW.
Comparing Generator Types and Brands
Portable generators provide short-term backup for small tools or outdoor use. For smaller households, the best-rated 4000-watt generator is ideal before upgrading to a larger standby model.
A whole-house generator starts automatically during power outages, providing reliable emergency power. Both portable and standby units can run on natural gas, propane, or diesel fuel.
When selecting the right size generator, consider factors such as power consumption, total power requirements, noise level, and fuel source. Grounded Electric’s guide on how to choose a generator for your home explains how to determine the size of a generator you need for consistent performance.
Safety and Installation
Only licensed electricians should install or connect a generator. Never attach a generator directly to your home’s panel without a transfer switch, as it can cause electrical hazards. Grounded Electric follows NEC sections 700 and 701 to ensure safe and compliant installations.
When choosing a generator, rely on expert guidance. Grounded Electric, led by Robert “Bobby” Mulholland and Barret Abramow, delivers code-compliant installations and trusted support to keep your home powered safely – even when losing power.
shedule a consultation or request a quote.Our licensed team will help you choose the right generator, review your power requirements, and ensure your system meets all safety and performance standards.
Frequently Asked Questions About the Generator Sizing Chart
Add up the running wattage for each appliance, then increase it by 20% to account for startup surges.
It can handle basic appliances, such as lights and a refrigerator, as well as small tools, but not all systems together.
Yes. An electrician ensures safe grounding, proper setup of the transfer switch, and compliance with local electrical codes.
