Determining the right size generator for your home’s needs depends on several factors. The most important considerations are the total wattage of appliances and devices you want to power, whether you’ll use the generator for backup power or as a primary power source, and if you need to power your entire house or just essential items.
How much power do I need for my house?
The first step is calculating the total wattage you need your generator to produce. This involves taking an inventory of all electrical appliances and devices in your home and adding up their rated wattage.
Some common household items and their average wattages:
| Item | Average Watts |
| Refrigerator | 500-2000 |
| Freezer | 500-2000 |
| Electric stove/oven | 2500-5500 |
| Microwave | 1000-1500 |
| Coffee maker | 900-1200 |
| Toaster | 800-1400 |
| Clothes washer | 350-500 |
| Clothes dryer | 1800-5000 |
| Dishwasher | 1200-2400 |
| Television | 100-400 |
| Desktop computer + monitor | 150-400 |
| Laptop computer | 20-100 |
| Ceiling fan | 50-100 |
| Table lamp | 60-100 |
| External hard drive | 10-30 |
| Electric water heater (while heating) | 4000-5500 |
Other devices like pumps, furnaces, and air conditioners will also need to be factored in if you want to power them with a generator.
As a general rule of thumb, you’ll want a generator that can produce around 3000 watts to power essential items like lights, a refrigerator, and select appliances during a power outage. To power an entire house, you’ll likely need 6000-8000 watts or more.
Do I need a standby generator or a portable generator?
The main types of generators for home use are:
- Portable generators – These range from about 800-5000 watts and are meant to be used temporarily or for specific applications like construction sites or camping. They can provide backup power but must be started manually and have the appliance plugged into their outlets.
- Standby generators – Permanently installed, they automatically turn on when the power goes out. Standby generators are connected to your home’s electrical panel to power hardwired systems andappliances.
For whole house backup, a standby generator is usually the better option. They can power more items simultaneously, turn on automatically, and don’t require extension cords. They also tend to be more powerful – often around 10,000 to 20,000 watts for most homes.
Portable generators are better suited for powering specific things occasionally, like tools or appliances after a storm causes an outage. They’re less expensive and easier to move around.
How is generator size measured?
Generators have their power output rated in watts. The two measurements to look at are:
- Starting watts – The maximum wattage a generator can output for brief periods when starting larger devices like refrigerators or air conditioners.
- Running watts – The continuous power output the generator can reliably produce over time.
You’ll want to select a generator where the running watts match or exceed the total wattage you calculated for your needs. The starting or “surge” watts just need to be high enough to briefly power the most demanding appliance when turned on.
What size generator is needed to run my whole house?
To determine the size for a whole house generator, add up the running wattage of all essential devices and appliances you want to power at once. As an example:
| Appliance | Running Watts |
| Refrigerator | 700 |
| Freezer | 500 |
| Lights | 500 |
| Television | 150 |
| Microwave | 1000 |
| Furnace fan | 800 |
| Sump pump | 1000 |
| Total running watts needed: | 4650 |
In this example, you would want a standby whole house generator of at least 5000 running watts. The starting wattage should be 6000-8000 watts to accommodate power surges.
As an estimate, a generator that can produce 8000-10000 running watts will be sufficient for most households to power lights, major appliances, heat, air conditioning, hot water, and other essentials.
Generator Size Recommendations by House Size
| House Size (sq. ft.) | Recommended Generator Size |
| Less than 2,000 sq. ft. | 8-12kW |
| 2,000 to 3,000 sq. ft. | 12-16kW |
| 3,000 to 5,000 sq. ft. | 16-24kW |
| 5,000 sq. ft. or larger | 24kW or more |
How much fuel consumption does my generator need?
Fuel consumption depends on the running watts and engine size. Most standby whole house generators run on natural gas or propane, which is supplied via an existing gas line to your home. Here are some typical fuel usages:
- 6-8kW standby generator – Consumes 180-250 cubic feet per hour of natural gas
- 15kW standby generator – Consumes 350-450 cubic feet per hour of natural gas
- 20kW standby generator – Consumes 500-600 cubic feet per hour of natural gas
For propane, an approximate fuel consumption guideline is about 36-44 gallons per 24 hours for a 15kW generator under 50% load. At full load, consumption may be around 60-70 gallons per day. Refueling needs vary depending on load.
Portable gasoline generators have fuel tank capacities ranging from 1 gallon up to around 8 gallons. At 50% load, a 5500 watt portable generator will consume about 1 gallon of gas per hour.
What features do I need in a whole house generator?
Key features to look for in a home standby generator:
- Auto Start – Automatically turns on when power is lost. Look for options like a battery charger to ensure startup.
- Transfer Switch – Safely transfers power from the generator to your home’s electrical system.
- Enclosure – A weatherproof steel or aluminum casing to protect components.
- Quiet operation – Noise levels around 60-70db, similar to a normal conversation.
- Remote monitoring – Mobile app or web-based monitoring of the generator status.
- Whole house coverage – Sufficient wattage and circuits for essential appliances and systems.
- Fuel source – Natural gas or propane hookup compatibility.
Additional useful features can include a battery charger, exercise mode to periodically test the generator, and extended warranties or maintenance packages from the manufacturer.
Where should I install a whole house generator?
The generator should be installed in an outdoor location like:
- Side yard
- Backyard
- Adjacent to exterior wall
It’s required to be a certain distance from doors, windows, and air vents for proper ventilation and exhaust. Make sure the location allows technicians good access for maintenance and repairs.
A concrete pad may be poured to create a solid, level foundation. The transfer switch is installed next to the main circuit panel or utility meter.
Generator Installation Tips
- Locate away from bedrooms or living areas to reduce noise disturbances.
- Keep protected from direct exposure to rain, snow, or flooding.
- Avoid placing beneath trees or overhangs where debris can fall on it.
- Pick a spot with good airflow and ventilation.
- Ensure the exhaust can vent safely away from the home.
- Have a supply of the proper fuel (natural gas or propane) available.
- Follow all local permit and inspection requirements.
How much does a whole house generator system cost?
A standby home generator typically costs $5,000 to $15,000 installed. Factors affecting the price include:
- Generator size – More wattage means a more expensive unit.
- Fuel type – Natural gas is often cheaper than propane.
- Additional features – Things like cellular monitoring can add cost.
- Professional installation – Required for permanently mounted standby generators.
- Permits and inspection fees – Varies by municipality.
- Scope of electrical work – New hookups, lines, and transfer switch expenses.
Ongoing costs will also include fuel, routine maintenance, repairs, and possible rental fees if you’re leasing the generator. Get multiple quotes to find the best value.
Average Home Generator Costs
| Generator Size | Installed Cost Range |
| 6 kW | $5,000 – $7,000 |
| 11 kW | $7,500 – $11,000 |
| 16 kW | $9,000 – $13,000 |
| 20 kW | $11,000 – $15,000 |
Can I install a generator myself?
Homeowners should not attempt to install standby whole house generators themselves. A professional electrician is required to safely connect the generator to your home’s electrical system and obtain permits.
Self-installation risks:
- Electrocution from improper wiring
- Fire hazards
- Carbon monoxide poisoning if ventilation is inadequate
- Failure to meet local codes
- Damage to electronics from power spikes
- Generator damage from improper loading
- Voided manufacturer warranty
Hiring a licensed, insured electrician ensures your generator is properly installed and hooked up to your home’s circuits for safe operation when needed.
How can I maintain my standby generator?
Proper maintenance is essential for your home generator to start and run reliably when required. Recommended maintenance includes:
- Exercise the generator monthly – Run it under load for 10-30 minutes to prevent oil seals from drying out and keep parts lubricated.
- Annual service – Have a certified technician inspect fluids, batteries, air filters, and other components.
- Fuel stabilizer – Add stabilizer to gasoline portable generators during extended storage to prevent stale fuel.
- Test carbon monoxide alarms – Ensure you have working CO alarms near bedrooms and the generator location.
- Address startup issues – Replace batteries and spark plugs if the generator fails to start promptly when tested.
- Inspect housing – Check for corrosion, cracks, or animal nests in the generator enclosure.
- Review warranties – Understand what maintenance is required to keep factory and extended warranties valid.
Following the manufacturer’s maintenance guidelines and having a trained technician do periodic service provides the best assurance your generator will work when the power goes down.
Conclusion
Choosing the right size home generator involves calculating your electrical needs, allowing for essentials like refrigerators, heating, and lights. For whole house coverage, expect to need a standby generator around 8-15kW. Work with an electrician to select a suitable unit and install it properly, as improper DIY installation can be hazardous. With routine maintenance, a properly sized and installed home generator will automaticaly power your household’s critical systems during an outage.
