Whole House Generators: Understand Installation, Benefits, and Costs

Whole House Generators in Detail

Automatic Standby Generators, commonly referred to as whole house generators add an obvious benefit to your home. If you’ve already read Automatic Standby Vs. Portable Generators, you’ll know that these units are more costly than their portable generator counterparts. Click here for details and installation information on portable generators. As of 2024, the most common unit (including the ATS) costs approximately $6200.00 to purchase, shipped to your home. Keep in mind this is the price of the unit and transfer switch without installation. I’m going to explain everything I know about whole house generators from my 20+ years of installing them.

What Size Generator For The Whole House

The size of an automatic standby generator and transfer switch is going to depend on the total load of your home as well as the size of your electrical service. Sizing of an automatic standby generator to power a whole house is a little more simple than portable generators because the generators can be had with much higher outputs. There is no moving them around, and the dimensions are typically about the same.

Depending on how much money you can afford to spend on the unit and how many electric appliances you have in your home, most people will purchase a unit that is between 10,000-22,000W (10KW-22KW). An electric range, air conditioning, and electric dryer are the three largest loads for your decision. If you want all three to work, you’ll need to be in the 20,000W+ range, if you simply want the generator to go on to protect your refrigerator, heating system, and other light loads while you’re on vacation for instance, a smaller unit will do you just fine.

Very large, “unnecessary” loads such as spas can be “locked out” by a special module to accommodate a smaller generator. The spa for instance would increase the size of a generator about 14KW! Lots of times the bottleneck becomes the size of the gas line feeding the house when large generators are installed. As always, speak to an electrician for more precise information on what you will need. Many times, you’ll buy a slightly oversized unit because they are more readily available and very similar in cost to smaller units. Check out our Electrical Registry to find a great electrician in your area that we recommend.

Installation of Automatic Standby Generators

To better explain the installation of the whole house generator as well as the automatic transfer switch (ATS), I broke it down in to three sections. Take a look at the following picture I put together as a reference point as the pictures in each section don’t show every electrical component in every picture.

Location and Base:

The location is dependent upon the requirements of the manufacturer as well as the town in which you live. A whole house generator typically need to be 5’ from ANY opening. An opening can be a window, door, vent, etc. Clearance to the back is 18″, to both sides and the front is 36″, and above is 60″. Before the generator is put in to location a suitable base is prepared. The base is usually a poured concrete slab, preformed foam/concrete slab, or 3/4″ gravel. Here are some examples:

Electrical Connection:

The unit is then connected to your home through an Automatic Transfer Switch (ATS), which acts as the new main disconnect. The install is between the electrical meter and your electrical panel. During the ATS installation, the existing electrical panel will need rewiring, as it will become a sub panel. This involves separating the grounding (ground) wires from the grounded (neutral) conductors to prevent objectionable current. Become an electrician or engineer if you want to learn more about that! Here are some pictures of the installation process and the completed transfer switch:

Plumbing Connection:

A plumber will have to connect the generator to the gas system of the house. Your plumber will tell you if you need to upgrade the gas meter. This is common because of the gas draw of a whole house generator. If you’re in an area with no natural gas you may need to have a separate propane company install a propane tank, either buried or above ground, and plumb it in. Here’s what a typical natural gas supply installation looks like:

Pros of a whole house automatic Standby Generator:

1. Effortless operation – Power goes out, power comes back on in just a few seconds. No need to go outside to turn on a portable generator. No need to be home. Big plus for folks who frequently travel and don’t want to worry about a power outage while away.
2. Reliability – Automatic generators are designed for maximum reliability. There is an “exercise” schedule where it will turn on, get fuel running through it, warm up, and make sure everything is functioning. No stale fuel, no wondering if the generator is going to work during an outage. If you know when the generator exercises (you can set it to whenever you prefer), you’ll have a good idea bout the health of the generator.
3. Connectivity – In today’s world of the Internet of Things, many devices can connect to automatic generators, allowing you to receive updates on your smartphone. Many newer generators come with a wifi module factory supplied.

Cons of an Automatic Standby Generator:

1. Cost – They are the more costly method of temporarily powering a home during an outage.
2. Location – You’ll need to devote a relatively open location to the unit. Some people consider it an eye sore but there are clever ways to hide it.
3. Service contracts – Not necessarily a con, but you will definitely want to pay for a service contract. This will ensure your unit has clean oil, air filters, and spark plugs all of the time. You will also get service immediately if your unit malfunctions during an outage.
4. Gas/Propane – You need to have a natural gas service at the home or you will need a large propane tank installed, typically underground.

Cost and Pricing

The vast majority of installations completely finished including the whole house generator range between $10,000-$14,000. Here’s the breakdown: At the time of writing in 2024, a 22KW Generac Generator costs about $6200 including delivery to your home. I expect this number to change as time goes on as it has increased substantially over the past few years (the technology has improved as well). In my experience Electrical Installation (as of 2024) is typically between $2500-4000, and the plumbing for natural gas is usually between $2000-4000.

Remember, it all depends on where the generator is located in relation to your gas meter and electrical panel. The further and more difficult it is to get either one of these components to the generator, the more expensive it will be for the installation. The condition of the gas and electrical services is a significant factor if they are old and need replacement (this can be a requirement of the utility companies).

Other Costs

Other factors to consider include the foundation. Most installations will include the price of a gravel foundation which is more than adequate and recommended by the manufacturers. However if you live near the water you may need an elevated slab installed by a masonry or concrete company which will add another cost factor in to the mix. If you install the generator with a bottled propane system, you will incur an additional cost for a propane company to install a large propane tank, which is sometimes buried underground.

Some companies will sell a whole package including the installation of the plumbing (natural gas or propane) and electric. This is great if they will install the unit and provide a service contract with it as well. The downside to this is any potential warranty issue. Is the electrical contractor prepared to work on the engine in an emergency? What if it needs repair during a storm when everyone else is most likely to need service too? Engine mechanics is outside of the scope of most electricians and plumbers. Purchasing from a big retailer can come with more assurance should you need immediate service.

Brands of Automatic Standby Generators

There are numerous brands out there producing and selling automatic standby generators and transfer switches that will support a whole house. I can tell you I’ve personally installed Generac, Briggs & Stratton, Westinghouse, Kohler, and CAT generators. The most common automatic standby generator setup my company installs is Generac. As a company, their marketing is superior and the products are great. I encourage anyone to buy the unit they want based on their own research. Consult with whoever is installing for their opinion as well. Common is good in this case! The installation process for the various brands is nearly identical. Some people prefer one brand over the other in terms of noise, size in some cases, and price. I plan to write an article comparing the various units commonly used for homes, but for now, I don’t have a specific opinion to share.

Closing Thoughts

It is my hope that the above will help you understand your options when selecting a whole house generator and electrician. I want to ensure you do not get taken advantage of during a generator buying frenzy as so commonly happens. As always, ensure you have a licensed electrician and licensed plumber doing the installations. We have a comprehensive list of Electricians that specialize in generator installs in our Electrical Registry here. If you have any questions feel free to leave a comment and I’ll respond as best and quickly as I can. Thanks for reading!