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Independent Power - Which Generator??

In my case I have PV solar panels and a large (3000 watt) wind turbine. You might be wondering why I'm bringing up a generator. After all, isn't solar power the most independent way to approach this problem? Aren't you just trading one dependency for another?

The reasons are as follows:

  • To provide immediate power while you build your system, which will usually take some time. This is especially true because it is difficult to determine at the beginning exactly how big a system you need. Almost everyone underestimates the size of the batteries they need, and the number of panels required, etc.
  • To provide emergency backup power in case you have an inverter failure, or severe weather that interferes with your ability to collect power..
  • To provide for power needs that exceed the capacity of your solar powered system.
  • In general, to allow you to handle emergencies that are not normal conditions. The unforeseen does occur and you want to be ready!
  • A generator provides an anchor for your whole system. Just as a generator is a good backup against an extended outage if public power fails, it's a good idea for you when you're living off the grid!

In fact, the very first purchase for your new system should be a generator. Then the idea is to build your system so that you use your generator less and less as time goes by.

Now that we've laid the groundwork and explained the need for a generator, let's decide which one to get and what it will cost.

Selection Criteria

I always like to keep things simple so I'll do my best here. There's a lot of thought and research that I've put into this over the years. So I'm going to give you my opinions here. As you look around for equipment always do your own thinking and be independent. I don't want anyone to just 'do as I say'. I'm giving you the benefits of my experience and an awareness of the issues so you can be better prepared to reason these things out for your self. I've also added links to equipment that represents the kind of choices available to you. You can take it from here.

  • Fuel Type - Ideally you want to use a fuel that you can safely store. When an emergency occurs you don't have time to dash out and fill some jugs. You need to have a reserve sufficient to get you by for a while... At least 72 hours.
    • Diesel
      • This is the best fuel there is for backup power. A typical diesel generator delivers nearly twice the power per gallon, when compared to gasoline. Diesel is a more powerful fuel, and diesel engines are high compression, so they burn fuel at higher temperatures releasing greater energy.
      • It stores for long periods and is a lot safer to handle and store than gasoline.
      • You can buy diesel without paying road taxes, which is a big savings in cost! Here the savings is about 70 cents per gallon.
      • In extreme cold climates an anti-gel additive might be needed so that the fuel remains fluid. Depending on how you store your fuel and the climate where you live this can be a critical issue. In most cases this is not a problem, just something to be aware of.
      • Diesel engines last much longer than any other engine type. They have dramatically fewer things to go wrong and run much better than gasoline in foul weather. The have no carburetor, no points or electrical system. All they need is fuel, air, and compression. The bigger water cooled units can run 20,000 to 40,000 hours before an overhaul. That's easily 10-20 times longer than a gas generator.
      • One of the explanations for longer life is the fact that diesel engines used for power generation usually turn at 1800RPM, some run 1200RPM, and Lister type diesels run as slow as 600RPM! As a general rule, the slower you go the longer you last. Gas generators (and a few small diesels) run at 3600RPM, which goes a long way towards explaining their shorter lifetimes.
      • Diesel generators are amazingly efficient. Load and fuel consumption track very closely, due to the nature of fuel injection and the fuel.
    • Gasoline
      • Gasoline has the advantage of being readily available, and in an emergency gas can be siphoned from a vehicle and used in the generator. (Buy a siphon kit!)
      • Be sure your generator is designed for cold and wet weather operation!! Some work great year around, but many cheaper generator imports from China do not run reliably in the winter or in wet weather conditions. The highest probability is that you'll need your generator and the weather will be bad. I've had very good luck with Briggs and Stratton based generators here over the years. They have dramatically improved bad weather operation, fuel consumption, reduced oil consumption, and are much easier to start than they used to be. The newer engines are excellent.
      • A good 5KW+ gas generator can be purchased for less than $1,000 and is nice to have around.
      • Gasoline generators often waste fuel when lightly loaded. This means that, for greatest efficiency you should keep a significant load on the generator, or turn it off.
    • Propane
      • Propane is an excellent fuel and can be stored indefinitely. Engines that run on propane last longer than gasoline due to the lubricating property of the fuel.
      • They often 'stink' when they run. Unburned gas has a smell.....
    • Natural Gas
      • Natural gas is a great fuel like propane, but you are dependent on the Gas company for delivery when you need it. In an earthquake or major calamity this could be a major issue.
      • They often 'stink' when they run. Unburned gas has a smell.....
  • Size
    • Decide how much power is the maximum power you will need and get a generator of that size.
    • You will quickly see that there is quite an increase cost with size. This should keep you from going overboard. I've found that a good 5500 watt generator works well for me here. We've owned 8-10 generators of a variety of makes and sizes, so we have a lot of experience here.
    • When we talk about inverters and electrical system issues I'll explain why 5KW is large enough for most of us. Especially if you are using an inverter and batteries.
    • If your generator is strictly for power outages and emergencies then you will need a larger unit, 12 to 24KW depending on how much power you need to run your home. Especially if your home is not very energy efficient.
  • Cooling
    • Water Cooled
      • Water cooled diesel generators are (with a few possible exceptions) much more reliable. Since there is more control over expansion and contraction of metal parts and such generators usually have full pressure lubrication, wear is under better control. Water cooled diesel generators are designed for more serious applications and are generally built to tighter specifications. Tighter tolerances can be more easily maintained because of a more constant operating temperature.
    • Air Cooled
      • If you are not going to need to run your generator that often, or you just want one for emergencies, air cooled generators are a good choice. They are cheaper to buy, and as I mentioned earlier they have improved a great deal over the last few years.
  • Noise
    • Most people will want an enclosed generator that runs quietly. You can build a little building to house your unit (there are critical safety issues here), but better yet I would advise that you buy one in a nice enclosure. If you live where neighbors are a long way from your house you can disregard this, but most of us have other people nearby and we all want to be good neighbors.
    • Some open frame generators are pretty quiet. Just look and compare based on published noise specifications. Lower is better.
  • Price
    • Don't be snookered by brand name or high prices. Some people sell generators for ridiculously high prices! Brand names are often hijacked by off shore companies trying to make money on an old reputation that is no longer valid. Take a little time and look around. There are some terrific deals out there.
    • Used generators are an excellent choice, particularly when you need a larger generator. Many are available on ebay, and other sites. Look for low hours, and well maintained equipment. Get advise from someone familiar with the the equipment before buying, but you can find incredible buys on gensets with a little hunting. i.e. There are a lot of Detroit Diesel based gensets around that are 20kw, and are built to last.
  • Maintenance
    • Even a cheap generator can last a long time if properly maintained. CHANGE THE OIL, use synthetic oil, and keep the generator clean. When a generator is used often you get more time out of the generator. What I'm saying is, run the generator every week for 15-30 minutes. Some generator systems do that automatically. Look for the feature.
  • Safety
    • Follow good safety guidelines, and make sure that your generator is installed properly, and well ventilated. It's better to get the advice of an electrician or mechanic that you know. Make sure that you do things right. It is easy enough to follow directions. Get a second opinion when you can. Always pick the safest option. Once you have your system in operation it will be there for years to come, so don't get impatient.
  • Specifications
    • Figures don't lie, but liars figure. That's an old axiom that's very true in today's commercial world.
    • When you look at the specifications of a generator make sure that the engine has a horsepower rating of 2HP for every 1KW of output. For example, a 5,000 watt generator should have at least a 10HP rating. Once you know this it's pretty easy to spot exaggerated ratings. Reputable companies will meet this standard, but there are many smaller companies looking for an edge in marketing that provide optimistic (to say it nicely) ratings.

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