When shopping for a generator, you'll notice two different wattage ratings: running watts and starting watts. Understanding the difference between these two specifications is crucial for selecting the right generator for your needs. Running watts represent the continuous power a…
When shopping for a generator, you’ll notice two different wattage ratings: running watts and starting watts. Understanding the difference between these two specifications is crucial for selecting the right generator for your needs. Running watts represent the continuous power a generator can provide, while starting watts indicate the maximum power output needed to start high-load appliances. This distinction can mean the difference between a generator that meets your requirements and one that falls short when you need it most.
Understanding Running Watts
Running watts, also called rated watts, represent the continuous power output your generator can safely sustain over extended periods. This is the most important specification for most users because it indicates how much electrical load your generator can handle during normal operation. When you’re using appliances like refrigerators, well pumps, or HVAC systems, they draw their running wattage continuously.
To determine the running watts you need, add up the wattage of all appliances and devices you plan to run simultaneously. For example, if you want to power a 5,000-watt air conditioner plus other household items totaling 3,000 watts, you need a generator with at least 8,000 running watts. It’s wise to choose a generator with slightly higher running wattage than your calculated total to allow for safety margin and future expansion.
Running watts are typically the lower number listed on generator specifications and represent what the generator can sustain indefinitely without risk of damage or shutting down. This is the rating you should focus on when planning your everyday power needs during an outage.
Decoding Starting Watts
Starting watts, also called surge watts or peak watts, represent the maximum electrical power your generator can output for a brief period—usually just a few seconds to a minute. Many electrical devices require significantly more power to start than to operate continuously. This surge of power is needed to overcome the initial resistance and get motors spinning in appliances.
Common appliances with high starting wattage requirements include air conditioners, refrigerators, well pumps, and power tools. For instance, a central air conditioning unit might require 15,000 starting watts but only 5,000 running watts once it’s operating. If your generator’s starting watts fall short, it won’t be able to start these appliances, even if the running watts are sufficient.
Starting watts are the higher number in generator specifications. The difference between starting and running watts varies by appliance and generator model, but generators typically can produce 1.5 to 3 times their running wattage for brief periods. Understanding your appliances’ starting requirements is essential for proper generator selection.
Calculating Your Generator Size Requirements
To properly size a generator, you need to account for both running and starting watts. Begin by listing all appliances you might run simultaneously during a power outage. For each item, research or check the nameplate for both running and starting wattage specifications.
Add up all running wattages for devices you’ll operate at the same time. This total should not exceed your generator’s running watts rating. Next, identify which appliance has the highest starting wattage requirement. Your generator’s starting watts must exceed this peak demand.
For example, suppose your simultaneous running wattage total is 6,000 watts, but your well pump requires 4,000 starting watts and your air conditioner requires 8,000 starting watts. You’d need a generator with at least 6,000 running watts and 8,000 starting watts. A 7,500-watt running/15,000-watt starting generator would be appropriate for this scenario.
To simplify this calculation process, you can use a generator size calculator tool that takes into account both specifications. These calculators help ensure you select the right generator by automatically accounting for both running and starting power requirements, making it easier to match your needs with available models.
Frequently Asked Questions
Q: Can I use a generator with starting watts lower than my appliance’s starting watts?
A: No, you cannot. If your generator’s starting watts are insufficient, it won’t be able to start the appliance, and attempting to do so may damage the generator or the appliance. The generator’s starting watts must meet or exceed the highest starting wattage requirement of any appliance you plan to run.
Q: Why is there such a big difference between running and starting watts?
A: Electric motors require extra power to overcome initial inertia and begin rotation. Once the motor is running, it requires less power to maintain operation. This is why air conditioners, refrigerators, and well pumps all have significantly higher starting watts than running watts. Generators are designed to handle these temporary surges without damage.
Q: Should I buy a generator based on starting watts or running watts?
A: You should consider both. Your generator must have sufficient starting watts to start your appliances, but the running watts must accommodate all devices operating simultaneously. Both specifications are equally important for proper generator selection. Choose a generator that exceeds both your calculated running wattage total and your highest individual appliance starting wattage.