Your power is out. The fridge is silent, the house is dark, and your phone is dying. You shouldn't have to worry about spoiled food or being disconnected.
To run a house, you need a Generator between 3,000 and 20,000 watts. A 3-5kW unit covers essentials like a refrigerator and lights. A 6-10kW unit adds more comforts. A 12-20kW generator can power nearly the entire home, including central air conditioning.
Choosing the right size can feel complex, but it doesn't have to be. I’ve spent my entire career in the generator industry, from the factory floor to founding my own company. I've helped countless clients find the perfect fit for their needs. Let's break this down into simple terms so you can make a confident decision. We will explore exactly what different generator sizes can handle, so you know what to expect.
What size generator is needed to run a whole house?
You want to power everything, not just the basics. A "whole house" solution sounds great, but picking the wrong size means you either waste money or don't have enough power.
To run a whole house, you will most likely need a 12kW to 20kW generator. This size can handle large appliances like central air conditioning, an electric water heater, and a washing machine running at the same time. It needs professional installation with an automatic transfer switch (ATS).
A Closer Look at Whole House Power
Running a whole house means you want life to continue as normal during an outage. You don't want to pick and choose which appliances to use. This requires a generator that can handle the massive power draw of multiple large items starting up and running together. Central air conditioners are usually the biggest energy hogs.
For a true whole-house solution, you need these key components:
- A high-power generator: Usually a 12kW to 20kW unit. These are often stationary models that run on natural gas, propane, or diesel.
- An Automatic Transfer Switch (ATS): This is the brain of the system. It detects a power outage, automatically starts your generator, and switches your home's power from the grid to the generator. When grid power returns, it switches back and shuts the generator off. It's a hands-free solution.
| Appliance Category | Typical Power Demand (Watts) |
|---|---|
| Central AC (3-5 ton) | 3,500 - 5,000W |
| Electric Water Heater | 4,500W |
| Electric Dryer | 5,500W |
| Refrigerator & Freezer | 800W |
| Lights & General Outlets | 1,500W |
This is why a powerful generator is essential.
Will a 5000 watt generator run a whole house?
A 5000-watt generator is a very popular and affordable choice. But you're worried it won't be enough when the power is out, leaving you to make tough choices about what to run.
No, a 5000-watt (5kW) generator will not run a whole house. It is excellent for basic backup power. It can run essentials like a refrigerator, lights, a sump pump, and a small TV. It cannot handle large appliances like central AC or an electric oven.
Making the Most of 5000 Watts
A 5kW generator is a fantastic tool for emergency preparedness, but you have to understand its limits. Think of it as a lifeline, not a complete replacement for grid power. You have to manage your power consumption carefully. This means you can't run everything at once. For example, you can run your refrigerator and lights, but you might have to turn off a window AC unit to use the microwave.
I had a client once who bought a 5kW unit expecting to run his small workshop. He quickly learned about starting watts versus running watts. His air compressor needed a huge surge of power to start, which the generator couldn't provide while the lights were also on. It's a common mistake. A 5kW generator is perfect for a "Basic Backup" scenario.
| Appliance | Can a 5kW Generator Run It? | Notes |
|---|---|---|
| Refrigerator/Freezer | Yes | A top priority. |
| LED Lights | Yes | Very low power draw. |
| Phone/Laptop Chargers | Yes | Essential for communication. |
| Sump Pump | Yes | Critical for preventing floods. |
| Microwave (1000W) | Yes | But not with other large items. |
| Central Air Conditioner | No | Requires far too much power. |
| Electric Water Heater | No | A huge energy user. |
A 5000-watt generator provides peace of mind by keeping your essentials running.
Will a 20k generator run a house?
You are considering a powerful 20kW generator. It seems like the ultimate solution, but you wonder if it is overkill. You don't want to spend money on power you won't ever use.
Yes, a 20kW (20,000-watt) generator will comfortably run most houses. It can power all major appliances at the same time, including central air conditioning, electric stoves, and water heaters. It is a true whole-house solution that gives you power similar to the utility grid.
The Power of a 20kW System
A 20kW generator is the top tier of residential power backup. It's for the homeowner or business manager who wants zero interruptions. This is more than just a generator; it's a complete power system. It's the right choice for large homes, homes with residents who rely on powered medical equipment, or businesses that can't afford any downtime.
With 20,000 watts, you don't have to manage loads. You can do laundry, cook dinner on an electric stove, and run the central AC all at once during a blackout. This level of convenience requires a professional setup. It includes an outdoor, weatherproof unit, often a quiet diesel or natural gas model, connected to an ATS. Some advanced systems even include load-shedding features to prioritize certain circuits, like starting the AC first to reduce the initial power surge's impact on other electronics.
| Typical Load in a Large Home | Running Watts |
|---|---|
| Central AC (5-ton) | 5,000 W |
| Electric Water Heater | 4,500 W |
| Electric Dryer | 5,500 W |
| Refrigerator & Kitchen Appliances | 2,500 W |
| Lights and General Outlets | 1,500 W |
| Approximate Total | 19,000 W |
As you can see, a 20kW generator handles this heavy load with power to spare.
Conclusion
Choosing the right generator means matching watts to your real needs. A 5kW handles the basics, 10kW covers more comfort, and a 20kW can power it all.
