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When the power goes out, having a generator on hand can be a game-changer, but choosing the right size is essential to keep your home running smoothly. Picking a generator that matches your power needs ensures you’re ready for anything, from keeping the lights on to powering essential appliances. With options ranging from compact models for basic necessities to larger units for whole-house coverage, it’s easy to feel overwhelmed.
This guide will walk you through the key considerations for choosing the right generator size. By understanding your home’s power requirements and the different types of generators available, you’ll be prepared to find a reliable solution that fits your lifestyle and budget.
How big of a generator do I need?
Generators come in different wattages, and the size you need depends on what you plan to power. Small generators can handle a few appliances, while a whole-home generator— or a standby generator—can power an entire house. Your needs will determine the size that’s right for your home.
Some of the most common generator sizes and their capabilities are as follows:
| GENERATOR SIZE | ||||
| 7,500 watts | 10,000 watts | 18,000 watts | 25,000 watts | |
| AC Unit | 2-ton | 3-ton | 5-ton | 5-ton |
| Kitchen | ✅ | ✅ | ✅ | ✅ |
| Furnace | ✅ | ✅ | ✅ | ✅ |
| Sump Pump | ✅ | ✅ | ✅ | ✅ |
| Bathrooms | 1 | 1 | 3 | 3+ |
| Bedrooms | 1 | 2 | 5 | 5+ |
| Living Areas | ✅ | ✅ | ✅ | ✅ |
| Water Heater | ❌ | ✅ | ✅ | ✅ |
| Home Office | ❌ | ❌ | ✅ | ✅ |
| Garage | ❌ | ❌ | ✅ | ✅ |
Note: These are estimates. Your home’s requirements will vary depending on your specific appliances and their power needs.
How Many Watts it Takes to Run a House
When sizing a generator for your home, you should account for both your home’s square footage and the appliances you’ll need during an outage. Larger homes tend to require more power, but it’s equally important to think about the specific devices you’ll be running.
Start by listing all the appliances you’ll need to power during an outage, then find the wattage required to run each item. This information can typically be found in the owner’s manual or on the appliance itself. To get an accurate wattage estimate, you can use a generator calculator or ask an electrician. A generator size chart like in the section above can also provide a helpful visual for determining the capacity of different generator sizes.
| Appliance or Device | Running Wattage |
| Coffee maker | 400 to 800 |
| Microwave | 1,200 |
| Refrigerator/freezer | 600 to 800 |
| Space heater | 1,250 |
| Toaster | 1,100 to 1,700 |
| Electric oven | 5,000 |
| Personal computer | 500 to 2,000 |
| Television | 100 to 350 |
| Table lamp | 150 |
| Hair dryer | 1,200 to 1,500 |
| Cell phone battery charger | 10 |
| Video game console | 200 |
| Washing machine | 750 |
| Clothes dryer | 1,500 to 5,000 |
If you’re concerned about overloading the generator, consider staggering the use of appliances or unplugging those that aren’t necessary. Don’t forget to factor in essential devices like a sump pump, which may be crucial during heavy rain or flooding.
| System | Wattage |
| Central air conditioning | 2,000 to 4,000< |
| Window air conditioning unit | 600 to 1,500 |
| Electric furnace | 5,000 to 25,000 |
| Water heater | 3,000 to 4,500 |
| Sump pump | 1,500 |
| Radiant heater | 1,300 |
| Outdoor lighting | 500 to 1,000 |
How to Calculate What Generator Size You Need
To calculate the generator size you need, start by adding up the running watts of all appliances you want to power. Then, identify the appliance with the highest starting watts (the extra wattage required to start the appliance) and add it to the total running watts. This will give you the total starting watts needed for your essential appliances.
Total Generator Size (Watts) = Total Running Watts + Highest Starting Watts
For example, if your total running wattage is 3,000 watts and the highest starting wattage is 1,500 watts, you’ll need a generator with at least 4,500 watts. This ensures you have enough power for both continuous operation and initial start-up demands.
Different Types of Generators
After calculating your total starting watts, you’ll be ready to select the right generator size. Aim for a generator that runs at no more than 90 percent of its capacity to prevent overheating and automatic shutdowns. There are several types of generators, each suited for different needs. These are the most common:
- Portable generators are compact units ideal for powering one or two essential appliances during an outage and are also great for outdoor activities like camping.
- Inverter generators are known for their quiet operation. They provide cleaner energy and are suitable for sensitive electronics. Inverter generators are portable, and good for powering multiple devices.
- Whole-house generators are permanent installations that are wired into your home’s power supply and can meet the power demands of an entire house. Standby models automatically activate during an outage for seamless backup.
- Solar generators are eco-friendly options that convert sunlight into electricity. While they may not handle high-demand appliances, they are useful for smaller devices and reduce reliance on fuel.
- Dual-fuel generators are versatile machines that can run on either gasoline or propane, providing flexibility during fuel shortages. They are ideal for medium power needs during outages.
Generator Safety Tips
While generators are reliable, it’s also important to exercise good judgment while using them. Safety is crucial. These best practices will help you operate your generator safely:
- Operate it outdoors only. Never run a generator indoors or in enclosed spaces, including garages or sheds, as it emits carbon monoxide. Place it at least 20 feet away from your home with the exhaust facing away from windows and doors.
- Use proper extension cords. Only use heavy-duty, outdoor-rated extension cords with your generator. Make sure that they are not damaged and capable of handling the load.
- Keep the machine dry and covered. Generators should be kept dry and protected from rain or snow. Use a generator tent or canopy designed for safe outdoor use if necessary.
- Avoid overloading it. Only power essential appliances and don’t exceed the generator’s rated capacity. Overloading can cause overheating and damage.
- Turn off appliances before starting it. Before turning on the generator, make sure all connected appliances are off. Start them one at a time after the generator is running to prevent power surges.
- Refuel carefully. Always turn off the generator and let it cool down before refueling to avoid igniting gasoline vapors.
- Install carbon monoxide detectors. For added safety, especially if the generator is running close to the home, install CO detectors indoors to alert you of any gas buildup.
By understanding your home’s power needs, calculating the total wattage, and following safety guidelines, you can choose the perfect generator for your needs. With the right preparation, you’ll be ready to stay powered during any outage.
