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How To Size A Generator To Minimally Meet Your Needs

PostPosted: Tue Mar 29, 2011 4:26 am
by jpf1030
Howdy All,
A friend from LA wrote to Starr asking how to determine what size generator she needed to run her frig/frzr, computer and cell phone. She also wanted to know about the quietest type generator. I wrote back, giving her a very basic primer on generator sizing and types. I barely scratched the surface, so if anyone has further questions, please reply and we will be happy to answer your questions. I have pasted my generator question response letter below. Please get prepared quickly...jpf
Howdy S.,

To be sure of the generator size you need, you need to check the label on your appliances. The labels will show the watts or amps of power that the appliance draws. If it does not show the watts, that is easy to calculate. I'm sure the items you want to run on are standard household 120 volts. The label will for sure show amps the unit draws. To get wattage, simply multiply the amps x volts. Example, if it is a 120 volt refrigerator that draws 10 amps, that would be 1200 watts. That is probably high for a newer energy efficient frig, but it is just to give you an example of how to calculate power requirements.

You can do this with your computer, cell phone charger and all other items you may want to consider. Once you add up all the power draws that would "have" to be on at one time, you will then have the total wattage generator you would have to have.

As far as quiet, the very quietest generators are the new inverter type like Honda and Yamaha build. There is a company on ebay that does a triple fuel conversion on them that is pretty cool. It enables you to run it on gasoline or propane, plus natural gas. The one advertised is the EU2000i, but they probably have the 3000 as well. I have seen a 5500 model also, but they are about $12,000. Here is a link to the smaller one on ebay... ... 35b0d9c3fc .

The Costco generator is cheaper than the inverter style, but will be a good bit noisier. You could also ask the sellers for the noise decibel rating on each to determine the percentage difference in noise level.

Hope that sufficiently answers your questions. We wish you guys the best of success in all your prepping.
I'm glad to see you doing things and not procrastinating like the masses of people.

Re: How To Size A Generator To Minimally Meet Your Needs

PostPosted: Tue Mar 29, 2011 1:23 pm
by montanamac
We have been living "off the grid" for a while so have some first hand experience to pass along.

1. You always use more power than you originally calculate ... so ... size your generator a bit larger than you think you will need. Don't go overboard ... use good judgment and common sense.

2. Gasoline, propane or diesel engines rotate the crankshaft so many time then they need to be rebuilt. It follows that an engine that runs at 1,800 RPM will last longer than one that runs at 3,600 RPM. If you buy a 3,600 RPM generator (most consumer grade generators are of this type) ... don't plan on running it day after day and year after year without replacing parts, rebuilding and/or possibly replacing the entire unit.

A friend of mine lives "off grid" and has gone through several of the consumer grade generators ... many simply are not designed for long term use and will not last.

3. If you have a well as your primary water supply ... don't forget to include your well pump in your calculations for sizing your new generator. Also note ... most well pumps operate on 220 volts not 110.

4. Don't buy a generator and simply store it away until you need it. Fire it up and use it as if it were an emergency situation.

Simulate an emergency and practice.

Figure out how you are going to connect your new generator to the loads you are going to operate. Don't wait til you need you new generator only to discover you need something else to make it do what you want it to do.

5. Remember to provide for the fuel you will need in an emergency situation and store it away. Gasoline and/or diesel does not store well over a long period of time without special attention. Here again ... plan ahead. As in food storage ... it is a good idea to rotate your stored fuel.

These are only a few items that come to mind and I am sure there are entire books written on this subject that are not covered in this short note.

One thing for sure .. if you get into an emergency situation where your new generator is actually needed ... it will be a life style adjustment that you will need to be prepared for.