The size a generator should be depends directly on your specific power needs during an outage. For a typical house needing to power essential appliances, a generator that can provide between 5,000 and 8,000 watts is often sufficient. However, larger homes or those wishing to run more appliances may require significantly more power.
Understanding Your Power Needs
Determining the right generator size starts with identifying what you need to power. Are you looking to keep just the lights on and the refrigerator cold, or do you want to run major appliances like air conditioning or a well pump?
- Essential Circuits: Powering only critical items like a refrigerator, some lights, a furnace fan, and necessary electronics requires less wattage.
- Partial Home: Running a larger selection of appliances, potentially including a window AC unit or microwave.
- Whole Home: Powering nearly everything in your house, similar to normal utility service. This requires a much larger, often permanently installed (standby) generator.
According to sources, a generator providing between 5,000 and 8,000 watts is typically enough to power a standard home's essential needs during an outage. Some homes may require more power usage and appliances during a power outage, while others may only need a few running. This range generally covers critical appliances like refrigeration, lights, and basic heating/cooling components.
How to Determine the Right Size
To accurately size a generator, you need to calculate the total wattage of the appliances you plan to run simultaneously. This involves understanding two types of wattage:
- Running Watts (Rated Watts): The power an appliance uses continuously while running.
- Starting Watts (Surge Watts): The extra burst of power many motor-driven appliances (like refrigerators, pumps, and AC units) need to start up. This is often 2-3 times their running wattage.
Steps to Calculate Your Needs:
- List Appliances: Make a list of everything you want the generator to power during an outage.
- Find Wattage: Find the running and starting wattage for each appliance (check the appliance's label, owner's manual, or manufacturer's website).
- Sum Running Watts: Add up the running watts of all appliances you might run at the same time.
- Identify Highest Starting Watts: Find the appliance on your list with the single highest starting wattage.
- Calculate Total Required Watts: Add the total running watts to the single highest starting watts. This sum represents the minimum size (in watts) your generator should be capable of providing. It's generally recommended to add a 10-20% buffer for safety.
Estimating Appliance Wattages
Here are some estimated wattages for common household items. Actual wattages can vary significantly by model.
| Appliance | Running Watts (Approx.) | Starting Watts (Approx.) |
|---|---|---|
| Refrigerator | 600 | 1200 |
| Lights (LED) | 10-20 per bulb | N/A |
| Sump Pump | 750-1500 | 1500-4500 |
| Furnace Fan (gas) | 400-800 | 800-2400 |
| Window AC (10k BTU) | 1200 | 3600 |
| Microwave | 800-1500 | N/A |
| Television | 100-300 | N/A |
| Coffee Maker | 800-1500 | N/A |
Note: Appliances with heating elements generally don't have significant starting watts.
Generator Size Categories
Based on typical needs, generators can be broadly categorized by size:
- Small Portable (1,000 - 3,000 watts): Suitable for camping, tailgating, or powering just a few critical items like lights and a phone charger.
- Medium Portable (3,000 - 6,000 watts): Can handle basic essentials like a refrigerator, lights, and potentially a sump pump or furnace fan. Falls within the lower end of the "typical house" range.
- Large Portable / Mid-Size Standby (6,000 - 10,000 watts): Sufficient for running more appliances simultaneously, often covering essential circuits for an average-sized home, aligning well with the 5,000 to 8,000 watts needed for a typical house's power usage during an outage.
- Very Large Portable / Standby (10,000+ watts): Designed to power most, if not all, circuits in a larger home, including central air conditioning and multiple major appliances.
Key Considerations
Beyond wattage, consider these factors when choosing a generator:
- Fuel Type: Gasoline (common for portable), propane, natural gas (common for standby), or diesel.
- Run Time: How long the generator can run on a tank of fuel at a given load.
- Noise Level: Generators can be very loud; consider decibel ratings, especially for residential use.
- Transfer Switch: For home backup, a transfer switch is necessary to safely connect the generator to your home's electrical panel and prevent backfeeding the grid.
- Budget: Generator costs increase significantly with wattage and features.
Getting Professional Advice
For installing a standby generator or if you are unsure about calculating your home's power needs, consulting a qualified electrician is highly recommended. They can help you assess your specific requirements and ensure safe installation.
