Whole House or Just the Essentials Generator Coverage?

Power Your Home Your Way

Image of the Cummins RS20A air-cooled home standby generator

This article focuses on the electrical circuits you deem essential and require power while on generator power. Many homeowners opt for Whole House or Managed Whole House coverage while other homeowners only require generator coverage for a few essential circuits. We will explore the differences between each to assist you in your search for a standby generator.

Whole House Generator Coverage

Whole House coverage means all electrical circuits in the house are connected through one or more Automatic Transfer Switches (ATS). If the home has a single 200-Amp Main Breaker Panel, a 200-Amp ATS will be required. In the case of homes with multiple main breaker panels, a transfer switch will be required for each panel. A standby generator is then sized to accommodate all potential loads.

So, Whole House coverage refers primarily to the required ATS gear. Potential electrical loads are then calculated to determine the generator size in kilowatts or kW (20kW, 30kW, etc.).

Avoid this mistake when shopping for a Whole House Generator (true story).

A homeowner still recovering from one too many power outages, walked into a Big Box store shopping for a Whole House Generator. The gentleman eyed three boxes each containing an air-cooled home standby generator and a 200-Amp ATS. Each box was marked in big letters “Whole House Generator”. The gentleman bought the lower cost “Whole House Generator”, loaded it on his truck and drove home before calling us for an installation quote.

Upon arrival, we learned the homeowner did indeed want whole house coverage for the 3500SF home which included a 5-ton A/C, two 3-ton A/Cs, and two Main Breaker Panels. We explained the transfer switch could be connected to just one of the Main Breaker Panels, so another ATS would be required. And, unfortunately, a 12kW standby generator was significantly undersized for his requirements.

Disappointed, yet thankful for the education, the gentleman returned the generator to the Big Box store, and we installed an appropriately sized whole house generator from Cummins.

If you are seeking whole house coverage, be sure to purchase a transfer switch for each installed main breaker panel. Potential electrical loads must be determined for generator sizing requirements. Stay tuned because we’ll jump into generator sizing in the next article.

Please note that a Sub-Panel is not a Main Breaker Panel. The circuit breaker feeding the Sub-Panel is found on one of the Main Breaker Panels. So, if an ATS is connected to the same Main Breaker Panel, electrical circuits on the Sub-Panel will be energized.

Managed Whole House Coverage

It’s important to understand which electrical loads require the most power to operate appliances and equipment. Central air conditioning equipment is typically the largest consumer of electrical power in most homes. Other appliances consuming large amounts of power include electric ranges and ovens, clothes dryers, electric hot water heaters, and electric heat. Light and receptacle circuits consume less power and can be estimated based upon the square footage of the home.

Homeowners desiring whole house generator coverage can save a bundle on overall project costs if they are willing to have the heavy-duty loads managed by the generator.

Managed Whole House coverage can be achieved with an air-cooled generator and Load Management Modules to manage the operation of high electrical loads. High electrical loads from an oven or electric clothes dryer might only work if generator power is available. If generator power is already operating at or near peak output, the generator will prevent these loads from working automatically.

To illustrate, let’s assume a 3500SF home has two 5-ton air conditioners and the homeowner wants a Whole House solution. To run both air conditioners at the same time plus other house circuits, a larger liquid-cooled generator like a Cummins RS30 might be required. The cost of a Cummins 30kW generator and switch is just under $14,500 plus installation. However, homeowners can save a bundle on project costs with a Managed Whole House solution using an air-cooled generator like the Cummins RS20A + ATS Kit, available on our website for under $6,000 plus installation.

Whole House Generator Coverage or Managed Whole House?

A Managed Whole House solution means the generator will manage the A/C loads for homeowners willing to have one A/C running at a time. The Cummins RS20A air-cooled generator can easily manage the job while saving thousands of dollars on overall project costs. When one A/C shuts down, the other A/C unit can start up and run, thus keeping much of the house cool during hot summer afternoons. The Cummins RS20A can also be programmed to prioritize which A/C is the highest priority. So, if the thermostat triggers the startup of A/C #1, it will automatically shut down A/C #2.

The potential savings for Managed Whole House coverage is just over $8,500.00 in equipment costs.

At this point, the homeowner needs to consider other priorities and ask, “Am I preparing for possible long-term power outages lasting a week or longer, or am I preparing for shorter duration power outages? Budget constraints play a key role, too. 

Coverage for Just the Essentials

Only selected Essential Circuits are energized by a generator for partial house coverage. A common illustration are homes with two or more 200-Amp Main Breaker Panels and the homeowner only wants to energize only one of the panels with the connected panel housing all essential circuits.

In this example, an electrician/generator installer can move circuits between the two panels, so each essential circuit is on the connected panel. Non-essential circuits on the other panel will not be connected to the generator, so only one transfer switch is required. The generator can then be sized to accommodate potential electrical loads.

Another example of Partial House Generator Coverage is moving all essential loads to a Sub Panel. The Sub Panel receives utility power for installed circuits through a circuit breaker installed on one of the Main Breaker Panels at the Service Entrance. These essential generator circuits can be moved from a single main breaker panel or from multiple main breaker panels and onto a single Sub Panel. Simply connect a Cummins Non-Service-Rated Switch or ATS to the Sub Panel so all installed circuits will be energized while on generator power.

Buckeye Power Systems recommends hiring an electrician with good experience installing a standby generator. Better still, hire a generator installer that is also an authorized dealer for the generator manufacturer. You will want to develop a long-term relationship with an authorized dealer to service the generator and make warranty repairs when and if needed.

Our next article will explore the different types of transfer switches and choosing the right switch for your installation.

Click here to go directly to the article on transfer switches.