Figuring out what size generator to use to run a house can feel confusing, especially when every appliance in your home pulls a different amount of power.
You want something that keeps your home safe and steady during an outage, but you also don’t want to buy more than you need.
My goal here is to help you sort through the basics in a way that feels clear and easy to follow.
I’ll walk you through wattage, common generator ranges, and a simple method to add up your own power needs. You’ll also see what size generator a typical 1,500 sq ft home usually requires.
By the end, you’ll have a solid idea of what fits your home.
Typical Generator Sizes To Run a House
Before you look at exact wattage needs, it helps to see how most homes fit into common generator ranges.
- 3,000–5,000 watts: Handles basic items like lights, a fridge, Wi-Fi, phone charging, and a small window AC.
- 5,000–7,500 watts: Covers the main items many homes rely on, such as a fridge, lights, Wi-Fi, a sump pump, and a few outlets.
- 10,000–15,000 watts (10–15 kW): Suits larger portable units or small standby units running more circuits and a small HVAC system.
- 15,000–22,000+ watts (15–22 kW+): Fits whole-house standby units that can run central AC along with many major appliances.
These ranges give you a simple starting point. Next, you’ll see how to match your own household needs to the right size.
Generator Basics: Size, Watts, and Load
Before choosing a generator, it helps to understand a few basic terms you’ll see when comparing wattage and appliance needs.
| Term / Load Type | What It Means | Why It Matters |
|---|---|---|
| Generator Size | The total power the unit can produce, measured in watts or kW | Shows how much your generator can handle at once |
| Running Watts | The power an appliance needs while it’s operating | Used to calculate your steady load |
| Starting Watts | A short surge is needed to turn on appliances with motors | Often sets the minimum generator size you need |
| Resistive Loads | Items like lights or toasters that don’t need extra startup power | Simple to power and easy to calculate |
| Motor Loads | Items like AC units, fridges, and pumps that need extra power to start | It can require 3–5 times more wattage at startup |
These basics make it easier to compare your appliance list to the right generator size in the next section.
What Size Generator Do You Need For a 1,500 Sq Ft House?
Square footage gives you a starting point, but it doesn’t show the full picture.
A 1,500 sq ft home can have very different power needs depending on climate, the number of large appliances, gas or electric systems, insulation, and layout.
A well-insulated home in a mild area may need far less power than a similar home in a hot or cold region.
Typical Wattage Ranges For a 1,500 Sq Ft House
These ranges help you see where most homes of this size usually fall before you do a full wattage list. Here’s what many homes around this size need:
- Essentials only: About 5,000–8,000 watts
- Essentials + window AC or mini-split: About 7,500–10,000 watts
- Whole-house with central AC or electric water heater: 12,000–20,000 watts
These numbers give you a simple guide, and the next example shows how they play out in a real setup.
Example Load Calculation For a 1,500 Sq Ft Suburban Home
This sample list shows how the numbers come together when you total both running and starting watts.
Appliance breakdown:
- Fridge: 700 running / 2,000 starting
- Microwave: 1,000 running
- Furnace blower: 600 running / 1,600 starting
- Window AC: 1,000 running / 2,000 starting
- Lights, outlets, Wi-Fi: 400 running
Wattage totals:
- Running watts: 3,700 watts
- Highest starting load: 2,000 watts
Minimum needed: 3,700 + 2,000 = 5,700 watts, Add a 20% margin → about 6,800 watts
A generator in the 7,500–10,000-watt range would suit this type of home and give you enough room for safe operation.
When You Might Need a Larger Generator
Some homes need more power than the standard ranges suggest, depending on the systems and equipment in use. Your wattage needs rise if you have:
- A two-story home with multiple HVAC zones
- A home with mostly electric appliances (stove, dryer, heat pump)
- A well pump, septic pump, and pool pump
- Heavy workshop tools or large power tools
These situations push your total load higher, so it’s safer to size up to avoid overloads during an outage.
How To Calculate What Size Generator You Need
Before you choose a generator, you can follow a quick set of steps to estimate the size you need.
Step 1: Choose what you want to power. Pick essentials only, essentials with comfort, or near whole-house.
Step 2: List your appliances. Note key items in the kitchen, living areas, and mechanical spaces.
Step 3: Check wattage. Use labels, manuals, or online specs to find running watts. You can also use the online wattage calculator from the U.S. Department of Energy to get quick estimates.
Step 4: Separate running and starting watts. Add all running watts, then add the highest starting surge.
Step 5: Add a margin. Increase your total by 20–25 percent for safety.
Step 6: Match the total to a generator size. Use the wattage ranges shown earlier to choose your size.
These steps give you a simple path to finding a safe and realistic wattage range for your home.
Types Of Home Generators & How Size Works for Each
Before choosing a generator, it helps to understand the main types available and how their power levels fit different home needs.
1. Portable Generators
Portable generators are common for short outages and basic home needs. They come in many sizes and are easy to move around the property.
They cost less than standby units but need manual setup, refueling, and outdoor placement. They also run louder and usually power fewer circuits than permanent systems.
Range: 2,000–10,000+ watts
Strengths: Lower cost, easy to move, flexible use
Limits: Manual setup, refueling, louder, needs cords or a transfer switch
2. Inverter Generators
Inverter generators make stable power that’s safer for phones, laptops, and other electronics. They run quietly and are fuel-efficient.
While their wattage is lower, many models allow pairing two units for more output. They work well for essentials, small homes, or short outages when noise control matters.
Range: Usually 1,000–5,000 watts
Strengths: Quiet, clean power, safe for electronics
Limits: Lower output, may need parallel units for larger loads
3. Standby / Whole-House Generators
Standby generators are permanent systems that switch on automatically during an outage. They run on natural gas or propane and can support most or all household circuits.
They offer steady, long-term backup for homes that need reliable coverage, especially where outages happen often.
Range: 10–26 kW
Strengths: Automatic, powerful, supports full-home use
Limits: Higher cost, requires installation, needs permits
4. Solar + Battery Generators
Solar and battery units store energy and deliver quiet, fume-free power. They can be charged by solar panels or the grid and work well for essentials like phones, routers, lights, and small appliances.
They are simple to maintain but don’t match the high output of fuel-based models.
Range: Varies by battery size, usually 500–5,000 watts
Strengths: Quiet, no fumes, low maintenance
Limits: Lower output, limited runtime without sun or grid charging
Factors That Change What Size Generator You Need
Several factors can change the size of the generator your home needs. This table gives you a quick look at what to consider.
| Factor | What It Means | How It Affects Generator Size |
|---|---|---|
| Climate & HVAC Load | Hot areas use more AC; cold areas use more electric heat | Higher HVAC demand raises wattage needs |
| Fuel Type & Efficiency | Natural gas, propane, and diesel each perform differently | Fuel type affects runtime, storage, and overall output |
| Electrical Service (100A vs 200A) | Larger services support more appliances | May influence transfer switch sizing and total load |
| Outage Frequency & Duration | Some areas lose power more often or for longer periods | Longer or frequent outages may need larger units or more fuel |
These points help you estimate the size that best fits your home and daily needs.
Key Safety Points Before You Install a Generator
When you set up a generator, a few safety rules are important:
- Transfer switch: Stops backfeeding and gives you a safe connection point.
- Ventilation: Portable units must run outdoors, well away from windows and doors.
- CO detectors: Add extra safety inside the home.
- Permits and pros: Standby units often need permits, and licensed pros handle safe installation.
These points help protect your home and ensure your system runs safely during an outage.
Mistakes To Avoid When Choosing a Generator Size
It’s easy to misjudge your power needs, and a few common mistakes can lead to poor performance or unnecessary costs.
- Choosing a generator that’s too small can lead to tripped breakers, power drops, and possible appliance damage.
- Going too large can raise fuel use and installation costs, though load management can help keep the size reasonable.
- Ignoring starting watts is another issue, since these surges are often the reason generators fail under load.
- Forgetting about future additions like a hot tub, workshop tools, an EV charger, or a finished basement can leave you short on power.
By keeping these points in mind, you can choose a generator that handles your needs today and still gives you room to grow.
Wrapping Up
Choosing what size generator to run a house becomes much easier once you understand your wattage needs, the loads in your home, and how starting watts change the total.
By now, you have a clearer view of the common ranges, the steps to size a generator, and what a 1,500 sq ft home may need during an outage.
My hope is that this gives you a steady foundation to make a choice that fits your home and your comfort level. Your setup should feel safe, simple, and ready when the power drops.
If you’d like more down-to-earth tips for your home projects, I’d be glad to have you check out more of my posts.
