Home generators provide backup electrical power in the event of an outage from your utility provider. They can be a safe and convenient way to wait for the power company to restore service. If you are looking for a quality installation of a generator or an outlet to connect your portable generator, you should talk to us.
What kinds of generator connections can I choose from?
There are three main approaches to connecting generators to a building supplied by utility power:
- whole home/property generator with automatic transfer switch
- critical load generator with automatic transfer switch
- portable generator with outlet and manual transfer switch (typically only powering a portion of a building load)
Automatic transfer switches enable the generator to automatically start itself when a utility outage is detected. The switch transfers the building power source (or a portion of the building) to the generator and returns it to the utility when stable power is available again. Based on the budget, the total load of the building, and potential savings from a critical load approach, the customer decides whether to support the entire building’s load or only the critical circuits.
Manual transfer switches are typically used when the customer wants to connect a portable generator to the building electrical system. During an outage, the customer connects the portable generator and uses the switch to manually transfer power.
Maintenance
Whether the generator is automatically started or manually connected and started, the generator requires maintenance to be able to run reliably when it is needed. Most require an annual service call and regular maintenance activities during periods of use.
Cost to Operate
Customers should also consider the operational cost of the solution, and we will help explain the pros and cons.
- As a fuel consumption example from Generac specification sheets, 10kW Guardian series uses 1.48 gallons of propane gas at 100% load, or 10kW, while a 16kW model uses 1.7 gallons at 50% load, or 8kW1. Therefore, the 10kW unit can more efficiently produce 10kW of electricity than the 16kW at reduced load.
- As an example of maintenance, the smallest Generac Guardian Series generator available in the U.S., a 10kW model, uses half of the oil of the 13kW-16kW models.
You should also consider how your generator will receive fuel as part of the cost calculation. You may have natural gas available at your home, or you may need to install a large propane tank. For portable generators, you would need to have fuel cans on hand.
Whole Building/Property Generator(s)
If the customer wants to live as if there is “no outage,” then a whole property standby generator may be appropriate. If the building has a 100 amp service, the entire property can likely be supported by a 16kW – 26kW air cooled generator, depending on fuel source. With appropriate automatic load management for large loads like HVAC, a 20kW – 26kW air cooled generator can support a 200 amp service.
Above 200 amps, things become more complicated, as single transfer switches capable of 300 – 400 amps are significantly more expensive, and two separate 150-200 amp transfer switches is likely going to be more cost effective than a single 300-400 amp transfer switch. Load management and load calculations become significantly more important in the 300 – 400 amp range, as a 26kW generator is only capable of producing around 110 amps on propane (propane produces more electricity than natural gas in the same generator; models are “derated” when running on natural gas), far below the sum of the maximum transfer switch circuit breaker ratings.
If you select Brighter Tomorrow Electric Company, you can rest assured that we will perform load calculations and consider load management to provide a range of solutions for you to consider. For some customers with service above 200 amps, such as 300 amp or 400 amp service, a Critical Load Generator solution is likely to be more cost effective, and offer adequate capability for a reasonable quality of life on standby power at a significant cost savings over the life of the generator.
Critical Load Generator(s)
Critical Load Generators are often used for a more cost-effective solution when there is a need for emergency standby power for critical items like well pumps, hot water heater, security/fire alarm, refrigerator, and convenience items like basic lighting, internet equipment, and a TV. As an example, a 10-16kW generator can run a well pump, sump pump, furnace, heat pump or AC, some lights, security/fire alarm, and a refrigerator with load management.
A critical load generator solution can also make a lot of sense when load calculations would dictate a generator with a capacity above 110 amps, as at around 110 amps is the maximum size of air-cooled generators available from the major manufacturers (Generac, Kohler, and Cummins) and liquid cooled generators, or a second generator, are significantly more expensive.
Manual Transfer Switch/Outlet for Generator
Some customers will already have a portable generator, and want to have a transfer switch and outlet professionally installed. Transfer switches are required for buildings that connect to the electric grid by the National Electric Code, as without one, you can inadvertently energize utility wires from the generator. To protect utility workers and your neighbors, you should have a transfer switch installed, and an outlet installed in a safe location that keeps carbon monoxide out of your building.
Manual transfer switches with portable generators can typically provide a maximum of 50 amps, and transfer switches are generally available in a variety of standard sizes such as 15 amp, 20 amp, 30 amp, and 50 amp, with options for 120 v and 240 volt generators. We can cost effectively setup a manual transfer switch and install an outlet that will meet code requirements.
- https://www.generac.com/generaccorporate/media/library/content/all-products/generators/home-generators/guardian-series/9kw-7029/generac-10-16kw-spec-sheet.pdf ↩︎