Permanent (stationary) generators are pre-wired to your home electrical wiring and hooked-up to a fuel line. Automatic systems are also referred to as standby. These systems can detect a power outage, start up and power your home or business during an emergency without your involvement. This buying guide provides comparison data and best prices on some of the popular brands. You can find of course all this information by yourself, but our review may save you hours of research. The rating chart is followed by a comparative analysis to help you choose the best system for your home. For my picks also see cheap generators page.
Last updated January 2018

(with links to spec, price & reviews)
SIZE inches NG USE
5735 GP17500
Generac® 17.5 run/ 26.2 start not included 48.5 x 31 x 39.5" n/a n/a Portable; 50, 30 & 20A outlets; battery
Guardian® 7036 Generac® 16 kW auto 100A 48 x 25 x 29" 309 107 Mounting pad included
40337 Briggs & Stratton 14.4 NG/ 17 LPG auto 200A
48 x 34 x 31" 244 113 Mounting pad
MG17001 Milbank 15.3 NG/
17 LPG
sold separate 48 x 34 x 31" 248 118
14RESAL Kohler® 12 NG/
14 LPG
auto 100A 48 x 26 x 29" 193 81 CARB compliant
8RESVL Kohler® 8.0 LPG/ 7.0 NG auto 100A 28 x 30 x 32.4" 99 64 EPA; digital controller
6237 Generac® 8 kW LPG/ 7kW NG auto 50A 48 x 25 x 29" 121 51.6 CARB, composite pad, low noise
RS13 13GSBA 6711 Cummins® Onan® 11 kW sold separate 53 x 43 x 34.7" 191 88 EPA, CARB; mounting pad


Depending on their engine, stationary emergency gensets can run on natural gas (NG), liquefied propane gas (LPG) or diesel. In this review we also included one Generac's gasoline-fueled portable model because it can be used as a whole house generator due to its high power.
Many residential fixed models are bi-fuel and can run on both gas and propane, although they are shipped configured for a particular fuel, usually propane. You will need to do a simple adjustment to convert from one type to the other. Note that the rated wattage varies slightly with the fuel: the chart above give both NG and LPG watts. Diesels are more reliable, but they are the most expensive. Because of their higher cost, they are more suitable for industrial applications. Standby devices under 20kW are normally air cooled. Gensets about 20kW are usually liquid cooled.
generator install quotes
Nowadays most standby models carry 5-year warranty, but you have to read fine print. For additional information and lesser known details also see our guide to best standby home generators. One of the most important things to determine when choosing your backup system is how much electrical power your home will need in emergency. Check out our sizing guide for the recommendations.

So, what brand to choose? The main U.S. manufacturers of gensets for homes are Generac®, Briggs & Stratton, Kohler®, and Cummins® Onan®. Most other brands are private labels. Generac® accounts for about 65-70% of all North America gensets sales. Its current home generator systems up to 30 kW are CARB-compliant, which is required for California. The new EPA requirements are expected to be harmonized with CARB, so eventually for newly designed or imported models similar emission limits supposedly will be required nationwide. Generally, as far as I can see, Generac's Guardian® series is sold at one of the lowest costs per kilowatt among top brands in 10-20 kW range. Any model from this product line can be a cost-effective solution for a typical private house or a small business. Guardian® packages comes in several basic types. Some of their models can be bought with an optional "smart" load management. It can temporarily shed non-essential circuits when the genset approaches its maximum capacity. This allows you to handle several a/c with a smaller system. People often buy a well-known brand name without actually checking what's behind it. GE used to sell Symphony® II 40380, which was actually built by Briggs & Stratton. Apparently, this arrangement did not work well-- their website states that GE Generators is now Briggs & Stratton. B&S also powers Milbank. Not surprisingly, Milbank generators characteristics are nearly identical to that of B&S.

Home generator guide
Generac® model 6237 received "Best Buy" rating from Consumer Reports magazine. Generally, a 7,000W part is good only for essentials. Of course, if you don't need to feed a central a/c or other large appliances, this model may be an excellent choice. Otherwise, an average home with up to 4-ton central air conditioner typically needs at least a 12 kW device. For 5-ton a/c you likely need even larger system, such as GUARDIAN® 16kW model 6461. To properly size a system for such motor-driven loads, see our guide to starting a/c and motors). Popular Kohler's 14RESAL was also recommended by CR magazine. Kohler® website says its units restore power in as little as 10 seconds. This brand has one of the best warranty in the industry and is a good choice too, although it seems to be somewhat more expensive. A number of models recommended by the consumer magazine, such as Kohler's 8.5 RES-QS7, Generac 6237, CorePower 5837 and Cummins 13GSBA-6722B have been discontinued since their last review. Commins still makes a similar model 13GSBA-6722, which works only on LP.

Of course, besides the purchase price, there are costs associated with the installation, which may run from $4,000 to $8,000. When you are choosing the size of your genset, you also need to check if your gas or propane service is sufficient to provide the required amount of the fuel. Our chart shows cubic feet per hour (CFH) for both NG and LPG. By the way, Briggs used to make a nice dual fuel 7 kW #40248, which offered flexible connection options. It included a propane quick connect kit that could get you up and running immediately from two BBQ tanks as if it was a portable genset with an option to connect to natural gas later on. Unfortunately, this part is discontinued.

Note that the manufacturers usually state rated power for 60 oF (15.5 oC) ambient at sea level. You need to derate available watts typically 3.5% for each 1000 ft (305 m) above sea level and 1.5% for each 10 oF (12.5 oC) rise in ambient temperature above 60 oF. So, a 15 kW device would provide only about 14.1 kW at 100 oF.


. If you want to buy online at a discount, in my personal view, this Home Improvement department is the best place to start your search. It has a wide selection of Generac® GUARDIAN®, Briggs & Stratton and other top ranking brands and numerous users reviews. Amazon offers free shipping on the gensets they carry. Of course, there are many other discount stores. If you prefer to have a local installer handle delivery and installation, please complete this free quote request. As far as I know, regardless on where you bought a system, you can normally either order the installation from their local dealer, or hire your own contractor.

All listed devices provide split single-phase 120/240VAC 60 Hz output.
Prices in the chart do not include taxes, shipping and installation, although some retailers may offer free shipping.
The devices compared here represent only a small sample of all available models and brands. For other models as well as official specifications, datasheets and warranty info visit the websites of the respective generator manufacturers.
The part numbers in our chart are arranged in no particular order. The data and features (including ability to run a specific size of central air conditioner) are based on the published specifications of the respective manufacturers or retailers.
No attempt was made to verify products compliance to their specs.
While all attempts are made to provide accurate, current, and reliable data, all info here is provided AS IS- we assume no responsibility for any errors. Product reviews are provided for information purposes and reflects only the opinion of the author. The sole responsibility when selecting a product rests with you.
Generac®, GUARDIAN®, Briggs & Stratton, Kohler®, Cummins® Onan®, GE and some other words mentioned above are registered or unregistered trademarks, trade names and service marks and are property of their respective owners.
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