[et_pb_section fb_built=”1″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n
This question comes to us often. Usually, someone has a specific need and wants to understand which generator they should buy. In most cases, they are looking for a generator to run a house, probably during a power outage. Since 2011, the Federal Emergency Management Agency recommends everyone have a backup source of power<\/a><\/strong> as part of their emergency preparedness plan.<\/p>\n Every generator has limited capacity. It might be less than 2000 watts, but it could be much larger. Generators in power plants have capacities rated in Megawatts.<\/p>\n 1 Kilowatt (kW) = 1000 Watts (W)<\/strong><\/p>\n 1 Megawatt (mW) = 1000 Kilowatts (kW)<\/strong><\/p>\n 1 Gigawatt (gW) = 1000 Megawatts (mW)<\/strong><\/p>\n In this text, when we talk about generators, appliances, and loads, we’ll specify power in watts. We’re only going to convert to kilowatts when mentioning standby generators.<\/p>\n Before we talk about how big of a generator do I need, we need to explain a few facts about generator capacity. Specifically, the difference between starting watts vs running watts.<\/p>\n [\/et_pb_text][et_pb_image src=”https:\/\/standbygenerators.org\/wp-content\/uploads\/2025\/01\/generac-gp18000efi-18kw-generator-50-amp-mts-1200×480-1.webp” alt=”A Generac 18000-Watt Generator and Manual Transfer Switch Prewired with Circuit Breakers and Wiring Whip, and 50-amp Generator-transfer switch cord” title_text=”Generac 18000 Watt with 50-Amp 10-16-circuit Prewired Transfer Switch” url=”https:\/\/norwall.com\/products\/generac-18000-watt-generator-with-cosense-gp18000efi\/” _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][\/et_pb_image][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n This Generac 18kW Portable Generator\u00a0 and manual transfer switch could power a home with a central air conditioner.<\/p>\n [\/et_pb_text][et_pb_button button_url=”https:\/\/norwall.com\/power-expert\/portable-generator-safety-rules-to-live-by” button_text=”Portable Generator Safety Rules to Live By” button_alignment=”center” _builder_version=”4.27.4″ _module_preset=”default” custom_button=”on” button_text_color=”#FFFFFF” button_bg_use_color_gradient=”on” button_bg_color_gradient_type=”circular” button_bg_color_gradient_stops=”#2b87da 0%|#18176d 100%” button_bg_color_gradient_end=”#18176d” button_border_color=”#000000″ button_border_radius=”20px” button_icon=”9||divi||400″ button_icon_color=”#FFFFFF” global_colors_info=”{}”][\/et_pb_button][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n Starting Watts is a specification that relates directly to electric motors.<\/p>\n Electric Motors have two power requirements.<\/p>\n Starting watts is the power a motor needs to start turning and reach rated speed.<\/p>\n<\/li>\n Running watts is the power a motor needs to run at rated speed under a full load.<\/p>\n<\/li>\n<\/ul>\n When a motor is not turning, the coils act like a short circuit. The current (amps) is high for a very short time, typically less than 3 seconds, but it could be longer for very large motors under load. Before the motor starts turning, starting amps is high and gradually reduces until the motor reaches rated speed, when it draws only the full load amps.<\/p>\n Amps x Volts = Watts.<\/strong><\/p>\n Example:<\/strong><\/p>\n A refrigerator has a motor that runs a compressor. A typical household refrigerator in North America requires 120 Volts and 6.66 Amps to run. However, the starting amps for a refrigerator might be two and half times the running amps, or 16.75 amps to start.<\/p>\n <\/strong><\/p>\n <\/strong><\/p>\n The refrigerator needs: <\/strong><\/p>\n <\/strong><\/p>\n If you want to run your refrigerator on a generator, it must be able to supply at least 800 running watts and at least 2000 starting watts.<\/strong><\/p>\n<\/blockquote>\n Important:<\/strong> Your refrigerator has specific power requirements. Use the information on the refrigerator’s appliance tag for the correct information. Appliance tags may refer to Locked Rotor Amps or LRA, and Full Load Amps or FLA.<\/p>\n Locked Rotor\u00a0Amps = Starting Amps.<\/strong><\/p>\n Full Load Amps = Running Amps.<\/strong><\/p>\n Multiply Volts x Amps to find Watts.<\/strong><\/p>\n Bottom line, a generator can only produce its starting watts capacity for a few seconds before its circuit breaker trips.<\/p>\n [\/et_pb_text][et_pb_button button_url=”https:\/\/blog.norwall.com\/generator-information\/dont-forget-starting-watts\/” button_text=”Generator Starting Watts” button_alignment=”center” _builder_version=”4.27.4″ _module_preset=”default” custom_button=”on” button_text_color=”#FFFFFF” button_bg_use_color_gradient=”on” button_bg_color_gradient_type=”circular” button_bg_color_gradient_stops=”#2b87da 0%|#18176d 100%” button_bg_color_gradient_end=”#18176d” button_border_color=”#000000″ button_border_radius=”20px” button_icon=”9||divi||400″ button_icon_color=”#FFFFFF” global_colors_info=”{}”][\/et_pb_button][et_pb_image src=”https:\/\/standbygenerators.org\/wp-content\/uploads\/2025\/01\/generac-powerpact-home-night-1200×630-1.webp” alt=”an Automatic Generac PowerPact 7.5kW Home Standby Generator Outside a Home at Night. The lights on are during a power outage thanks to the Generator” title_text=”Small Automatic Home Standby Generators Are Economical to Purchase and Install” url=”https:\/\/norwall.com\/categories\/standby-generators\/8kw-generators\/” _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][\/et_pb_image][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n A smaller automatic home standby generator keeps your house powered, even if you’re not there to fuel it or connect it.<\/em><\/p>\n [\/et_pb_text][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n Read the specifications for any generator you’re about to purchase. Different manufacturers use different labeling. Manufacturer X might name their generator for the MAX watts, or starting watts while Manufacturer Y uses a Running watts convention.<\/p>\n Another example is a generator capable of running on different fuels. As a general rule, portable generators produce the least amount of power on natural gas. Propane produces more than natural gas but less than gasoline. The manufacturer will probably name the generator for gasoline rated watts or starting watts. The 10,000 Watt Tri-Fuel that you intend to run primarily on natural gas may only produce 8000 watts.<\/p>\n 1000 Watts (W) = 1 Kilowatt (kW)<\/strong> [\/et_pb_text][et_pb_image src=”https:\/\/standbygenerators.org\/wp-content\/uploads\/2025\/01\/generator-starting-watts-running-watts-1200×220-1.webp” alt=”Generator Running Watts and Peak (Starting) Watts for a Tri-Fuel Generator with values given for gasoline, propane, and natural gas.” title_text=”Peak (Starting) Watts vs Running Watts for a Tri-Fuel Generator” url=”https:\/\/norwall.com\/categories\/portable-generators\/tri-fuel\/” _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][\/et_pb_image][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n Check the Generator Starting Watts and Running Watts Capacity Before You Purchase a Generator.\u00a0 Note the significant difference between fuels for this tri-fuel generator. Decide which fuel you will use the most, then choose accordingly.<\/em><\/p>\n [\/et_pb_text][et_pb_button button_url=”https:\/\/blog.norwall.com\/generator-information\/generator-watts-volts-amps\/” button_text=”Understanding Generator Power: Watts Volts Amps” button_alignment=”center” _builder_version=”4.27.4″ _module_preset=”default” custom_button=”on” button_text_color=”#FFFFFF” button_bg_use_color_gradient=”on” button_bg_color_gradient_type=”circular” button_bg_color_gradient_stops=”#2b87da 0%|#18176d 100%” button_bg_color_gradient_end=”#18176d” button_border_color=”#000000″ button_border_radius=”20px” button_icon=”9||divi||400″ button_icon_color=”#FFFFFF” global_colors_info=”{}”][\/et_pb_button][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” custom_css_free_form=”#appliance {|| font-family: Arial, Helvetica, sans-serif;|| border-collapse: collapse;|| width: 100%;||}||||#appliance td, #appliance th {|| border: 1px solid #111;|| padding: 8px;||}||||#appliance tr:nth-child(even){background-color: #f2f2f2;}||||#appliance tr:hover {background-color: #ddd;}||||#appliance th {|| padding-top: 12px;|| padding-bottom: 12px;|| text-align: left;|| background-color: #3a609c;|| color: white;||}” global_colors_info=”{}”]<\/p>\n What size generator should I buy for home backup is a frequent question on a popular Q&A site. Sadly, more often than not, the answers given are short and provide too little information. Many answers specify a 3000 or 4000 watt generator as more than adequate.<\/p>\n Let’s look at the power requirements of a few home appliances, including a gas furnace, that we want to run with our generator during a power outage.<\/p>\nStarting Watts vs Running Watts<\/h2>\n
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<\/strong><\/p>\n\n
Generator Capacity in Watts or Kilowatts<\/h2>\n
10,000 Watts (W) = 10 Kilwatts (kW)<\/strong>
10,000W = 10kW<\/strong><\/p>\nHow Much Power Do I Need?<\/h2>\n