If you are looking for a generator to provide backup power for your entire home or to charge batteries when renewable (solar, wind, hydro) are not available then here are some factors to consider when choosing the size and fuel type of a whole home backup generator:

1. Power requirements: The size of the generator should be chosen based on the power requirements of your home. To determine the power requirements, you will need to calculate the wattage of the appliances and equipment that you want to power during an outage. It is important to allow for some extra capacity to account for unexpected power needs or changes in equipment over time. If you have motor starting loads (well pump, washing machine, refrigerator compressors, etc), then the generator will need extra capacity to handle the surges when starting these devices.  H and K can help you to determine the power requirements of your home by installing a monitoring device on your electrical system and plotting out the load requirements for a few days to understand the needs of the home.  If the generator will also be used to charge a back up battery bank then it needs to be appropriately sized to match the length of time you require the battery to be charged while still powering the home.

2. Fuel type: Generators can be powered by a variety of fuel types; including gasoline, diesel, propane, and natural gas. The fuel type should be chosen based on the availability, storage and cost of the fuel, as well as any environmental concerns. For example, natural gas generators may be a cleaner and more cost-effective option, but they require a utility natural gas connection. Diesel generators may be more efficient and have a longer lifespan than gasoline generators, but they may also produce more emissions. Gasoline engines tend to be back up generators and not a primary power source. Gasoline is also highly flammable and does not have good long term storage capabilities.  

3. Revolutions per Minute (RPM): Is a factor in determining the life span of the generator.  Typical diesel generators run at 1800 RPM and have a longer life expectancy than a 3600 RPM gasoline generator.

4. Automatic transfer switch: An automatic transfer switch (ATS) is a device that automatically switches the power supply from the grid to the generator when there is a power outage. An ATS is an important safety feature for a whole home backup generator, as it ensures that the generator is only used when necessary and prevents back feeding power onto the grid, which is dangerous.

5. Typical Sizes:  Standard house size generators are in the range of 6 Kilowatts – 15 Kilowatts.  

6. Efficiency: This is the conversion of fuel type energy to electrical energy.  A diesel 1800 RPM generator has been the standard for most efficient conversion of fuel to electrical energy and remains true to this day at about 30%, with propane and natural gas as the middle ground and unleaded being about 15% efficient.  But efficiency is also affected by the load on the generator; so matching the size of the generator to the load requirements is a consideration.   

Overall, it is important to carefully consider the size and fuel type of a whole home backup generator based on the specific power requirements and constraints of your home. H and K can assist with your decision and recommend the most suitable generator for the application.