Wednesday, February 24, 2010

Buying a Right Sized Generator

All of us have had the experience of having the power go out. This summer we had a short outage of an hour or so. One minute Annie was sewing, the lights were on, the computers were on and the TV might have been on as well. The next minute - Nada. The house was dark, the sewing machines were off, the computers were dark and quiet. I think I might have been working on supper, but with no stove, that quickly came to a halt. We wandered around for a while, wondering what had happened, and when the power would be restored.

After a few minutes I saw a neighbor who has a police/fire/emergency scanner, and who's husband is a Deputy Sheriff - she often knows what is going on. She said that a fire in a neighboring town had burned down a half a dozen power poles, and it would be Monday before they got them repaired. My conclusion was that it might be Monday (it was Saturday afternoon) before we got our power restored. I don't know how long it took to actually fix the poles and line, but they were able to re-route power to town in an hour or so, and we went back to normal living.

But I have pondered that all winter long. Every time I put a log on the fire, or turned on the furnace I thought - what would we be doing if we didn't have power. If for some reason, in the middle of the winter, we lost power it would be a pretty dark and cold house. If we didn't get it back in a day or two, I would be draining the waterlines and the water heater - you don't want to think of the pipes freezing in your walls, breaking in several places, and then soaking your house down when the power came on, and things warmed up a little. We are fairly lucky to have most of our pipes in the interior walls. We can easily let our house temperature go to 45 or probably even 35 before we would worry too much about frozen pipes. Some of my friends aren't so lucky, and in their new homes, they have all the pipes routed in their outer walls.

Summer time is easier - maybe not too comfortable, but we could probably find a way to can/bottle most of the food in the freezer if we couldn't run the refrigerator/freezer.

So these musings led me to the KSL Classifieds and the search for a generator. I quickly found that there is a huge variety in generators, and they vary widely in price as well. I worked through a lot of scenarios of how much load we would need/want and confused my self some in the process, but finally came to a conclusion, at least about how to calculate the load.

Load, or watts are found by multiplying amps x volts. We are only calculating load for 120 volt loads, so that makes things a little simpler. I don't know how much load my furnace takes, or my water heater, but I know they have run for years on a 15 amp breaker. So I know they are less, and probably quite a bit less than 15 x 120 or 1800 watts. Because they have motors in them, I'm going to leave the estimate at 1800 for extra safety when starting. Motors draw extra current when they start. The bigger the motor, the bigger the power spike.

I know that everything in my list will run on 15 ampss, as they have for years. So they are not tripping the breakers, and hopefully the generator motor will take the load. Here is my little worksheet. There are three scenarios here.

  1. I've got to have everything on the list running all the time.
  2. OK, I can do some trading of loads to buy a smaller and cheaper generator.
  3. Economy - only the essentials. But I can still trade one for the other. Cheapest option.



Generator Scaling Worksheet




Winter - Gotta Have It All Mode

Furnace 15 x 120 = 1800 watts
Water Heater 15 x 120 = 1800 watts
Wood Stove Fan 15 x 120 = 1800 watts
Freezer 15 x 120 = 1800 watts
Refrigerator 15 x 120 = 1800 watts

Total 9000 watts = 9 kw

Summer

Whole House 15 x 120 = 1800 watts
Swamp Cooler 15 x 120 = 1800 watts
Freezer 15 x 120 = 1800 watts
Refrigerator 15 x 120 = 1800 watts
Water Heater 15 x 120 = 1800 watts

Total 9000 watts = 9 kw



Can Get By With A Little Less

Winter

Furnace or Water Heater 15 x 120 = 1800 watts
Wood Stove Fan 15 x 120 = 1800 watts
Freezer or Refrigerator 15 x 120 = 1800 watts

Total 5400 watts = 5.4 kw

Summer

Whole House or Swamp Cooler 15 x 120 = 1800 watts
Freezer or Refrigerator 15 x 120 = 1800 watts
Water Heater 15 x 120 = 1800 watts

Total 5400 watts = 5.4 kw


Winter - Economy Mode

Furnace or Water Heater or
Freezer or Refrigerator
15 x 120 = 1800 watts

Wood Stove Fan
15 x 120 = 1800 watts

Total 3600 watts = 3.6 kw

Summer - Economy Mode

Whole House or Swamp Cooler or
Freezer or Refrigerator or Water Heater
15 x 120 = 1800 watts


Total 1800 watts = 1.8 kw


Annie will probably note that I don't have the hair dryer and curling iron on the list.... but they can be traded, and she is always beautiful anyway. So there you have it. You can get a 3.6 kw generator for a few hundred dollars, probably about the price of a new iPod or Blackberry. But seriously, if you need it, there will be very few things you would trade for it. More later on this adventure.

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