Backup Home Generators: Make Mine a Diesel

One topic that doesn't necessarily fall into the realm of energy conservation is what I guess I'd call energy "preservation" - what you do when the grid power goes down and the lights go out. To this point, my family and I have just sat around in the dark using whatever candles or battery powered lights we had handy. But after a major power outage (some folks were out over two days) last winter that had us shivering and wondering if we'd have to abandon our home for a couple days, I decided that we wouldn't be in the same situation this year.

But, as I found out, not all home backup generators are created equal, and there are choices you can make that will influence how economically and ecologically friendly your backup generator will be.

Most sites start you out with figuring out how much power you need. In my case, I'm going to start out with the type of fuel. Your main options are gasoline, diesel, or natural gas/propane.

Initially, I was leaning strongly toward one of the standby backup generators that run on natural gas (or, if you have it, propane). Our house is served by a natural gas line for the furnace and stove, so that looked like a good possibility.

However, after investigating it some more, that option started getting really expensive really fast. One of the smallest generators you can get (7000 watts continuous power) is around $2000, then you have the installation costs to go with it. I was also a bit leery about how much natural gas these things consume and how much I'd wind up paying over time to maintain one (they usually come on automatically and run for a modest period of time once every week or two) and then to run it during power outages.

It would be cleaner burning than the other options, but to me this seemed like more of a "high end" option than my wallet was happy with, particularly after getting a quote for an installation that - although it included the 7000 watt generator - ran up to around $6,000. I'm sure it could be done a lot cheaper, but I shied away from that option.

Between the two remaining ways to go - gasoline or diesel - in my humble opinion, there really isn't a real choice: a diesel backup generator is the only way to go. This may seem like a small issue but many others such as myself prefer to know what we are dealing with. has a few various information concerning this topic. Here are a few things to consider:

1. Diesel backup generators, like most diesel engines in general, can use biodiesel or a mix of biodiesel and petro-diesel (or "dino-diesel") without any modification to the engine or fuel system. Gasoline backup generators don't really offer any other options, as - just like gasoline engines in cars - they can't run on pure ethanol without significant modification (and I don't happen to like ethanol as an alternate fuel, unless you live in Brazil). So right there you can help take a small bite out of our fossile fuel follies. Now, the down side here is that the exhaust from diesel generators is not nearly as "clean" as their modern automotive cousins. While they put out less in the way of greenhouse gasses like carbon dioxide, the exhaust has more particulates than gasoline generators. But, on balance - and in consideration of the other factors, below - I looked on this as an acceptable negative.

2. Diesel generators have much better fuel efficiency than gasoline backup generators of comparable wattage. For example, the diesel generator that I chose from Aurora Generators (more on that later) is rated at 6800 watts continuous power and is rated to run 12 hours under full load on 3.3 gallons of diesel fuel.

By comparison, a slightly smaller gasoline generator that I was looking at earlier (6,000 continuous watts) was advertised to run for 9 hours at 50% load on 6 gallons of gasoline. Now, if I'm figuring this right, this works out to a consumption rate of roughly 0.275 gallons per hour for my diesel generator versus 0.67 gallons per hour for the gasoline generator (which in this case produces 800 watts less).

Again, if my math is right this all works out to roughly 25 kilowatts per gallon for the diesel (100% load) versus about 4.5 kilowatts per gallon for the gasoline generator (50% load). Granted, your mileage is going to vary, but in my research diesel backup generators were consistently more fuel efficient than gasoline generators. The upshot is that not only are diesel generators significantly cheaper to operate, but for a homeowner this also means that you don't have to store nearly as much fuel for a given amount of run time, or fill up the tank as often. To me, those are significant factors.

3. As a general rule, diesel generators are much more reliable. There are obviously going to be exceptions based on quality of manufacture, but assuming proper user care and maintenance and all other things being equal, a diesel in general will long outlive a gasoline engine. Diesel engines also have a strong reputation for operating in less than ideal conditions, and are designed to operate under heavy continuous loads. Since I was looking for a generator primarily to keep my family warm and safe in the winter (other times of year the main concern is saving what's in the refrigerator and freezer), this was the third strike against gasoline powered generators after bio fuel and fuel consumption considerations: I wanted a generator that I could count on to run - and keep running under heavy loads - when I needed it. Usually this might be just a few hours now and again with local power outages. But with a major ice storm or hurricane, where the power could be out for days, I decided to hedge my bet with diesel reliability and performance.

4. On the downside, diesel backup generators tend to be a bit more expensive. However, in my case I tend to be an "investment-minded" person when looking into these sorts of things: I'll willingly pay more up front if I think the return over time will be worth it. In the case of a diesel generator for my family's needs, I feel very comfortable that I made a good investment. The generator that I bought was probably about $300 or so more than the nearest gasoline backup generator competition, but I feel that was money well spent.

That was the thought process that led me to choose a diesel backup generator over a gasoline powered one.

Then, of course, is how to figure out which generator to buy: while the selection isn't quite as bewildering as with gasoline generators, there are still a lot of different diesels to choose from.

At this point we get back on the traditional "how to figure out which generator you need" by calculating how much power you'll need. There are lots of sources on the web for doing that, so I'm not going to cover it here except to say that unless you're really strapped for money, don't be afraid to spend a bit extra for a larger generator if you think you might need it. You don't want to go overboard, but it makes more sense to me to have a little extra wattage available (heck, share it with your neighbor to keep their fridge cold!) than to not have enough.

Some other things that you should consider include:

1. Electric start. Like me, you've probably heard the sound of your neighbors heaving mightily - and repeatedly - on their generator pull-start cords, muttering curses in between their ragged breaths. This, my friend, is not for me! Once I decided to go diesel, it was a very short decision loop that put having one with electric start (although with pull-cord backup). I'm comfortable with my masculinity, but I don't want to wrestle with a balky generator when it's cold, dark, raining, etc. This is especially the case with a diesel, because the mass of the engine that you have to crank is a bit bigger than with a gasoline backup generator. Just let me turn the key (or, better yet, get one with a remote!), have the starter motor turn the sucker over and get it going.

2. Glow plugs. These preheat the air going into the combustion chamber to help ensure easier starting in cold weather. Note that these are "additional accessories" on many diesels, but unless you live in a really warm climate I'd strongly recommend that you make sure your diesel generator comes with them.

3. Hour meter. One of the biggest factors with any engine is maintenance, particularly when to change the oil. Our cars have odometers, and generators and many other engines have meters showing how many hours they've run. This is very useful to make sure you change the oil on time!

4. Automatic low oil pressure cut-off. While this seems to be a fairly standard feature, you should make sure that any generator you consider has it. That way if the oil runs low - which means that the engine will start to run too hot - the generator will automatically shut down and prevent damage.

5. Open-frame or "silent." A "traditional" open frame generator can be fairly loud, whereas a "silent diesel generator" that is enclosed and has additional sound baffles produces signifiantly less noise. As you've probably guessed, these are more expensive and a bit bulkier. But if you have the extra money and have a good place to put one, a silent diesel generator might be a good option, particularly if you're in an area where noise is an issue, even during a power outage.

And with that, I'll conclude this first entry on getting a home backup generator. In upcoming articles, I'll be doing a review of my diesel generator from Aurora Generators, cover power distribution using a manual transfer switch, and how to set up your generator in a ventilated enclosure.

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