Backup Power Generation Considerations, by Tractorguy

Emergency backup power is a key consideration in prepping for emergency situations and disasters. This is not meant to be a exhaustive discussion of different types of generators and backup power systems, but rather a discussion about critical items in an emergency situation.

Backup power is a two-edged sword. Many people think they are ready for a power outage because they own a generator, with no consideration given to proper connection, maintenance, fuel availability, or operation. I have been maintaining generators and backup power systems for more than forty years as a broadcast engineer and engineering consultant, and I can tell you I have seen many more backup power failures than successful generator operations in power outages.


Generator fuels can be divided into two groups – liquid (gasoline and Diesel) and gaseous (natural gas and LP). Each has their advantages and disadvantages, and operational considerations. One main driving force behind your choice is what fuel you already have and are used to handling.

Gaseous fuels have the advantage of being easy to handle, clean-burning, and in the case of natural gas, nearly constant availability in non-spicy times. If you have existing natural gas or LP service, you already have a good fuel supply for a generator. A gaseous-fueled generator can quickly be switched from natural to LP gas with a piping change and a minor readjustment of the mixer (the “carburetor” for gaseous fuels). LP gas has an indefinite shelf life.

However, from a prepper standpoint, there are some serious disadvantages to gaseous fuels. The recent situation in Texas should be a reminder that natural gas might not be available under all circumstances, and certainly will not be reliable in a grid-down situation. In a grid-down event, LP gas resupply will probably be nonexistent as well. You can store a lot of it pre-disaster, but afterwards, what you have is probably all you will have. Refilling LP tanks to transfer fuel is possible, but requires hardware and knowledge that you will need to accumulate now, not later. Small leaks in gaseous fuel systems can go undetected, so keep an eye on your fuel supply and don’t automatically assume that you still have X amount of fuel if you haven’t checked it for a period of time.

Keep in mind also that running generators off of portable LP tanks has some complications. The standard 15 lb. barbeque tank is insufficient for all but the smallest generators – those little tanks just can’t liberate vapor from the liquid fast enough to keep up with demand, and will quickly get cold and stop outputting vapor altogether. The amount of gasified LP that a particular tank can supply is dependent on ambient temperature. If you are running in cold winter temperatures, the tank size required is much larger than what is necessary in warm weather, to allow for sufficient vaporization to keep up with the generator demand.

LP-fueled generators consume a lot of fuel. If you are considering LP as a generator fuel, do some research into what your proposed generator consumes at various loads, and how many hours of operation you will expect out of how much fuel you will typically have on hand. If you are planning on transferring gaseous fuels in a grid-down situation, then get a “nurse hose” (a.k.a. “wet leg”) with matching connectors for your system, and learn how to use it correctly. The life you save may be your own!

Liquid fuels have similar advantages and disadvantages. Liquid fuels can be much more easily transported, and don’t require pressure vessels to do so. There was a picture that made the rounds on the Internet some time ago that showed someone filling open 55-gallon plastic garbage cans in the back of a pickup truck from a conventional gasoline pump to transfer fuel. Obviously, that is not advisable, but it is possible – the point here is that liquid fuels can be transferred in many different types of clean, hopefully sealed, containers. Gasoline powered portable generators are common. Your own gasoline-powered vehicles are a potential source of fuel for a while, as long as you have a siphon hose to retrieve it. Like natural gas, gasoline is readily available now, but will probably disappear quickly in a grid-down situation. Gasoline has a notoriously short shelf life when not stored correctly, and gasoline generators need to be either exercised regularly to keep the fuel in the carburetor fresh, or have their carburetors drained to keep them from getting gummed up from stale gasoline, which obviously renders them not immediately available when needed.

Diesel generators are typically more heavily built, and the engines are more efficient than a spark-ignited engine, due to their higher compression ratios, and the fact that there is more energy in a gallon of diesel fuel than a gallon of gasoline. They can easily be fueled from a home furnace fuel tank. They have the downside of being smelly and loud, and need to have careful maintenance on fuel systems to keep them reliable. Diesel fuel has a long shelf life when stored correctly, and you shouldn’t have to worry about diesel fuel going bad in an engine’s fuel system as long as it is exercised every few months.

You need to have consumable maintenance items on hand, such as air, oil, and fuel filters, engine oil, and fan belts (if used). When the grid goes down, what you have will be all you have.

Connecting to Loads

The generally-ignored part of emergency power systems is how to connect them to the intended load. I read several stories here on SurvivalBlog about people in last winter’s Texas disaster that had generators, but couldn’t use them because they didn’t have a way to connect them to their critical loads. Obviously a whole-house transfer switch is best and most convenient, and can be as simple as interlocked breakers in your existing circuit breaker box (check local codes to be sure). If you’re going to power your loads from extension cords, then have them on hand, tested, and ready to go.

One easy trick to automatically ‘load-shed’ your high power demand loads (usually the 240V ones) is to configure your generator for 120V output, and on the generator input side of your transfer switch, tie both legs of the 240V service together and feed them with the 120V generator output. This will power all the 120V loads as before, but the 240V loads will have no voltage across them and will be automatically inoperable.

If you have to keep refrigerators and freezers running, one of the handiest things you can have is a remote reading thermometer and alarm on each refrigerator and freezer. This will tell you the temperature inside without having to open the doors. If you are only running your generator part of the time in an extended outage, the thermometers will tell you how much you need to provide power to them to keep them safely cold, and when they have cooled back down to the original set-point temperature. For instance, I found in one extended outage that my big freezer, that I normally kept at about 5 degrees F, would warm up to about 25 degrees in 12 hours, and would cool back down to 5 degrees in about two hours of operation.

EMP and CME Events

Finally, since we are looking at preparedness for a major disaster such as an EMP (Electro-Magnetic Pulse) or CME (Coronal Mass Ejection) event, the susceptibility to failure of delicate solid-state electronics in your backup power system to these power surges cannot be overemphasized. You need to have an electrically-shielded enclosure – a Faraday cage – to store sensitive electronics NOW, before they are lost to an EMP or CME power surge. This can be as simple as a metal garbage can with a tight-fitting lid, with the items stored inside kept insulated from each other, such as in cardboard boxes. Search ‘Faraday Cage’ on the Internet for further information.

However, in the event of a high field strength EMP/CME event, the following will likely be damaged or destroyed:

1. YOUR SPARK-IGNITED (GASOLINE OR PROPANE/LPG FUELED) GENERATOR’S IGNITION SYSTEM. Unless your engine has a magneto and mechanical breaker points, your electronic ignition system will probably be destroyed. Get a spare and put it in your Faraday cage.
2. YOUR DIESEL GENERATOR’S GLOW PLUG CONTROLLER. If you have a Diesel generator, and it has a glow plug controller more complex than just a high-current relay, it will probably be destroyed. Get a spare and put it in your Faraday cage.
3. YOUR GENERATOR’S BATTERY-CHARGING ALTERNATOR (if so equipped). If your generator has an alternator on the engine to charge the starting battery, it and its regulator will likely be destroyed. Get a spare and put it in your Faraday cage.
4. YOUR GENERATOR END’S VOLTAGE REGULATOR. If your generator end has an electronic voltage regulator, not a simple capacitor-type regulator with current transformer compounding to correct for load changes, it will probably be destroyed. Get a spare and put it in your Faraday cage. If you have a brushless generator end with rectifier diodes in the rotor, make sure you have spares for those too.
5. YOUR GENERATOR’S DIGITAL METERING AND CONTROL. If your generator has any kind of digital metering, or a solid-state control system (such as an electronic governor), it will probably be destroyed. Get spares and put them in your Faraday cage.
6. YOUR TRANSFER SWITCH ELECTRONIC CONTROLS. If you have an automatic transfer switch, and it has any kind of electronic control other than relays, those will probably be destroyed. Get spares and put them in your Faraday cage.
7. YOUR SOLAR PANEL CHARGE CONTROLLER. Especially if you have a MPP charge controller, where the panel voltage is a lot higher than the battery voltage, failure of that item will stop your batteries from getting charged. This is a good argument for having a conventional charge controller, which can be bypassed in an emergency to continue to charge the batteries (see my earlier article on solar power). Either way, get a spare and put it in your Faraday cage.
8. LED LIGHT BULBS. Many of these have some electronics in them. Get spares and put them in your Faraday cage.
9. SOLID-STATE RADIOS. They should be stored in your Faraday cage when not in use. I also make it a point to disconnect the outside antenna from my tube radios, just in case.
10. TEST EQUIPMENT. DVMs and any other test equipment with electronics should be stored in your Faraday cage.

Load Testing Exercise

Finally, generators and backup power systems need to be exercised to keep them in tip-top shape and confirm that they are all ‘ready-to-go’ when needed. Seriously consider having a ‘grid-down’ day, or weekend, regularly. Pull the main breaker on your house panel, and go through the process of actually running off of emergency power. Make sure all your critical loads are powered. Note how much fuel you use. Monitor your generator carefully for operational problems (overheating, inability to handle full load, etc.) that may only show up under load.

Remember that exercising a generator no-load only confirms that the engine runs and the gen end makes power without load. That’s not to say that it isn’t vitally important to do so, but realize that all that you are confirming is that it runs without load. Running it under load confirms that it functions under load, but remember that running it under load for x amount of time only confirms that it will run under load for x amount of time, and no longer. I have seen untold examples of fuel transfer pumps that were not wired to run off emergency power, and when the day tank ran dry, the generator stopped, even though there was fuel available in the main storage tank. I have seen installations where the generator intake air was too close to the exhaust air output, and the unit ran fine for a while before it eventually overheated. This is why running the unit under load for an extended period of time is so important for confidence in your system.

Good luck and God bless!