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(206) 329-2040

SME Inc of Seattle offers our customers a broad and deep range of electrical services across commercial and industrial industries and residential properties. From tenant improvement, new build or renovations to assembly lines, healthcare facilities or multi- or single-family residences, the team at SME Inc provides experienced engineers and licensed electricians who have the skill and expertise to design, install and complete any project.

Generator Selection Standby Generators

Generator Selection - Standby Generators

Selecting The Right Standby Generator

Standby generators or automatic generators power your electrical panel and are connected 100% of the time. Standby generators also require an automatic transfer switch, which gives you hands free power whenever there is a disruption in electricity to your home. Automatic generators are rated in kilowatts, which measure the generators power capacity and its load capacity.


Like portable generators, you will have to decide what you will want powered in case of a black out. The appliance that will take the most power will be your electric air conditioner or heater.

Your air conditioner, electric heater or heat pump is rated in Amps, BTUs or Tons and this information usually is found on the unit's data plate. Alternately, you can look at your electrical panel to find out if your HVAC system uses a 30, 40 or 50–Amp double–pole circuit (240–volt). To understand the electrical requirements of other appliances, click on our Generator Sizing section for more information.

The general rule of thumb is, if your HVAC unit is a:

  • 3–Ton unit it uses a 30–Amp breaker, or 36,000 BTUs and will require a generator of at least 14kW
  • 4–Ton unit it uses a 40–Amp breaker, or 48,000 BTUs and will require a generator of at least 17kW
  • 5–Ton unit it uses a 50-Amp breaker, or 60,000 BTUs and will require a generator of at least 20kW

In some areas of the U. S., people may choose not to power their HVAC system. In southern states, you may not want to be without air conditioning in the summer and in northern states, you may not want to risk being without heat during the winter. Consider the likelihood of a long–term power outage and then choose an automatic generator based on the kilowatts needed to run your HVAC, appliances and lighting. SME Inc. can help you figure out what your power needs are and what generator size is right to meet these requirements.


Most likely, your home's circuit breaker is either a 200–Amp or 100–Amp service. This means the maximum amount of electricity that can be consumed at any one time is either 200 or 100–Amps. You don't use the maximum amount of energy continuously in your home so again, you will have to make a decision based on percent of load you want your standby generator to be able to handle.

Based on the general rule above:

  • A 14kW generator can power 58% of the load of a 100–Amp panel or 29% of a 200–Amp panel
  • A 17kW generator can power 71% of the load of a 100–Amp panel or 35% of a 200–Amp panel
  • A 20kW generator can power 83% of the load of a 100–Amp panel or 41% of a 200–Amp panel

SME Inc of Seattle can help you decide what size generator will fit your backup electrical needs for your budget and peace of mind. We install and service all makes of generators and we are select and certified dealers for Generac generators. Call SME Inc. at 206-329-2040 for a consultation regarding a standby generator today.