It is important to purchase a generator system that is reliable over time as well as cost-effective at the time of purchase. Startup, maintenance and repair costs will affect the overall cost of a generator system tremendously and this varies tremendously between brands and fuel types (diesel, natural gas and/or propane). To help decide which type of fuel is best for a specific situation/site, please refer to this page and then come back to help decide which brand and model are best for you.

With many generators, major components are eerily similar or even identical between brands. So while a few brands will use premium engines, enclosures and/or alternators (and we applaud this), the generator's control components are commonly the biggest noticeable difference between generators, as they are rarely even similar between major brands. In fact, the quality and design of the generator's controller is usually the deciding factor in what makes one generator superior to another. That is why the generator's control components are often the most important consideration (more important than purchase price) when choosing which generator brand to purchase.

Ideally, the generator's controller and associated electronics will be open architecture, meaning that anyone can gain full access to all of the controller's programming functions. In comparison, many major generator original equipment manufacturers (OEMs) provide proprietary controllers that they lock, hide features and documentation and otherwise restrict access so that only those technicians authorized by that manufacturer can access that manufacturer's controllers. Any programming or troubleshooting often requires perpetual use of that manufacturer's certified technicians (with special programming dongles, laptop software and passwords). Some manufacturers only allow their direct employees access to these critical functions, while others require the controller have an internet connection in order to activate its more desirable features. Even acquiring a basic manual of the controller often requires taking a class or is not available at all to the end-user. So be sure that you enjoy dealing with the OEM for the generator you're purchasing (and that they will be around for as long as you own your generator - crystal ball, anyone?) because, with most major brands, you remain tethered to that OEM or their dealer in one form or another for the life of the generator. On the contrary, when you purchase a generator with an open architecture controller, you can choose who performs your programming and maintenance instead of having to use specific, OEM-approved dealers.

For those in the market for new custom generators and are considering several different brands: Our advice is to specify that every field-service level of the controller's software must be accessible to you. If the controller on a generator only allows you access to a 'customer' level but making any changes or replacing the controller requires access to a level to which you will not be given access, there are three options you should consider:

  1. Purchase a (possibly different brand) generator with a controller that you or any technician you choose can access all field-service features and whose controls are fully documented.
  2. Require that the generator provider give you full access to the controller (as well as all diagnostic and other manuals for the controller) for the life of the generator
  3. Require that the generator provider guarantee free access for the life of the generator (i.e. will provide a free emergency on-call technician 24/7/365 for any incident where you require access but the controller denies permission). As companies come and go, this guarantee should include a bond for enough money to pay for a controller conversion to an aftermarket controller, should that generator provider ever fold or otherwise fail to fulfill his guarantee.

Some will suggest that it is no problem if you are on good terms with your generator supplier. But things change and even large companies go out of business. We see generators in the field all the time where the once-mighty manufacturer went out of business, just stopped providing generators and/or stopped supporting generators they produced. Some examples: MTU, Coleman, Elliot-Magnetek, NorthStar, Electro-Motion, Ingersoll-Rand, SimPower, etc.

Then there is the issue of convergence. In the last few years, this has become a significant source of problems. It may be a good idea to have GPS, cameras and other various features merged into a cell phone, which most replace every year or two anyway. However, you likely wouldn't want your stove, refrigerator and toaster merged into one unit. Besides the awkward physical appearance, it doesn't make sense to merge components with completely different lifespans and costs into one unit, especially if your desire is to use each until they fail (Oh my, the toaster in my stofridgoaster shorted out again - can anyone loan me another $2,000?). Even if merging the devices saved you 30% overall when purchased, with a generator, the controllers are designed so that when one sub-component breaks you are usually stuck replacing the entire unit. While not many understand and even fewer speak of these issues, it remains true that a generator's control components have varying lifespans, some of which are relatively short. Yet the trend with many generator OEMs has been to merge many of these separate devices (i.e. governor, voltage regulator, engine controller, battery charger) into one controller unit, presumably to save on manufacturing costs.


For example, the battery charger is frequently the 'Achilles Heel' of generators, as the charger often has a short life. Say, for example, that a generator's battery charger sticks on fast charge. The charger could not stay connected and would have to be disabled/replaced to prevent the generator's battery from potentially exploding. If it were a separate component and not part of the controller, a simple replacement charger starts at under $30 at local stores and almost anyone could replace it in a few minutes. On the other hand, when the charger is integrated into the generator's controller unit, the entire controller unit may have to be replaced. In fact, to guarantee that replacement would be necessary, some OEMs will have the controller provide a constant alarm that cannot be dismissed when a sub-component either fails or is disabled. They do this so that there can be no work-around and a new controller must be purchased. Since exact replacement controller units can only be ordered through the OEM, OEMs often inflate controller prices to around $700-$4,000 just for the controller -plus- having to wait several days for it to arrive (if the OEM is still in business and if that OEM still produces it at all) -plus- several hours labor for an OEM-certified dealer with special training, laptop software, programming dongles and passwords to program your new OEM controller unit.

If the proprietary OEM controllers that came stock on major brand generators were superior, there would be a demand for them to be installed on generators to replace "aftermarket", open architecture controllers. As it turns out, we have never even heard of any generator with an aftermarket controller ever being replaced by a proprietary OEM controller. On the contrary, we have to stock many aftermarket generator controllers because we have had so many requests to have various proprietary OEM controllers from major manufacturers replaced by aftermarket controllers (i.e. Deep Sea, Dynagen, ECU). Keep in mind that, while it is relatively easy and inexpensive to specify a new generator with a quality aftermarket controller, it is always more expensive to perform this upgrade in the field. The fact that there is a significant demand for a controller upgrade service in the field, despite its relatively high cost, attests to the level of motivation some have to part ways with their proprietary (and frequently unreliable) OEM controllers.

Warranty can be another big issue. Dynagen, for example, leads the way with a generous five year warranty for their generator controllers. Contrast that with most OEM controllers, which usually carry somewhere between a 90 day to a six month warranty. It is not uncommon for us to have to replace unreliable OEM controllers repeatedly, as controllers from some less reputable OEMs have a reputation for working just long enough to get past the warranty period.

Controllers that are able to be successful in aftermarket sales have other inherent benefits besides nearly unlimited features, reliability, open access, intelligent design, quality and warranty. Because there is competition between aftermarket controller manufacturers, their prices are also competitive, usually between $200-$400. They are often available from multiple sources, so you can choose your vendor. Lastly, because they are well documented with good installation instructions and support, aftermarket controllers are easily upgraded or otherwise exchanged for another brand, should a controller ever be discontinued. Our experience indicates that generators with aftermarket controllers like Deep Sea and Dynagen are the most desirable. While there is simply no downside to purchasing a generator with "aftermarket" control components pre-installed, we do not recommend blanket replacement of all OEM generator controllers in the field because of the cost, provided the OEM controller has the features you want and is working reliably for you. However, if you are like many whose controllers lack features, reliability or availability, there is no question that we can provide the controller upgrade you need on a moment's notice.

Please keep in mind that we have techs certified on all major brand generators and their controllers including CAT, Onan, Kohler, MTU, Generac and more. Regardless of which generator you own or which controller it has, we are able to provide you with the best after-sales support. We at AAAA Generator Services believe we are the best value for your startup, maintenance and service. We also believe the company you use to maintain your generator should earn your business, year after year.