I live in St. Louis city where power lines are above ground and we have a lot of old trees.  It's just a matter of time before we get hit with a power outage.  I'd like to be able to live as comfortably as possible.  If I want to run my a/c and/or furnace, I think I'll need a pretty expensive unit.  Am I right about that?  I don't want to spend more than $700-$1k, but would like to spend less.  So, if I want to be able to run a large refrigerator/freezer, fan, interior lights, spce heater and charge cell phones, what do I need?  Based on some rough calculations, I think a 7,000 watt unit would suffice.  What do you all think?  What about if I want to wire it in to my breaker panel?

Thanks guys.

Here's a very rough estimate.....bear in mind...your particular house may need more or less.


The average house in the city will run the basic appliance necessary to make life bearable for a min of about 2000 watts.  3500 watts is better and will give a larger cushion.  If you have central AC, you need a lot of watts.  You can do it but you'll pay for it.  Better to just have a small room AC and just cool one room if you must have AC.  If you have a regular gas furnace, you can run it on a generator easily.  You need to know if it's a 240 volt or a 120 volt furnace.  If you have a heat pump or electric furnace, better come up with another plan to heat your house with.  

If you have a well, then you're gonna need a bigger generator.  5500 is probably the min and might need more.

A standard electric water heater draws 4500 watts and a high recovery water heater will use about 5500 watts.  

I have an all electric house and I can run it on a 5800 watt running generator.  However, when the water heater is running, there isn't much power available for anything else.  I can't run the central heat so I have a pellet stove.

To run it into your panel, you need a generator transfer switch.  I personally like the 200 amp whole house transfer switches but there are smaller ones that will just run a few circuits.

The A/C unit is going to be the wildcard, perhaps you can find some specs on it. I would bet startup draw on a big unit might even be as high as 7kw just by itself.

As a example: We had a tornado two years back, I ran 3 refrigerators, lights, portable fans, sump pump, laptop, networking gear, cell chargers, battery chargers from a 5500 watt and it acted like nothing was there.
If you can forgo the A/C you could save a lot of money and also get a more efficient generator.

Briggs and Stratton website has "selecting a generator" section to help decide. Depending on how comfortable you want to be, you may be able to stay between 700 to 1k. 6500 watt unit ran fridge, portable 5k ac, a few lights and still had enough to run elderly neighbors fridge next door when we were powerless.

This...........forget the A/C.  If the power is out that long, you will figure out that you are living the high life (relative to everyone else)!  The AC will at least double your load and thats not even considering the in-rush to start it up.  Think of it this way, you still got cold beer, steaks in the freezer and pretty much anything else you want with ~5000 watts.  A/C is strictly a nice to have and doesn't save you any money by saving your freezer or making your house livable in the winter.  You can complain to all the neighbors and relatives how tough you have it without A/C if it ever happens.  

Something to consider IMHO is that you don't want to run your gen at or near full capacity for any significant period of time...  I try not to exceed 80% of full capacity...  so one of the rules of thumb I find useful is that, at a minimum, you want a generator that can put out at least 125% of the single largest load that you will want to run during an outage...

In terms of A/C - you will find that central A/C sucks too much wattage to be practical to use on gen power unless it is a really small central A/C unit - 1 ton or so...  but you can get away with a window unit in a bedroom so you can sleep comfortably at night and have a cool refuge in the day time...

Yep. In fact, if it's a central air unit, it could be several times that amount, easily.

One alternative is to buy one or two small window AC units, and then set them aside for use exclusively with your generator. A 5,000 BTU window unit will do a surprisingly good job of making a large bedroom comfortable, even if it isn't capable of cooling the room down to 60 degrees - Dehumidification does the trick.

Small window units don't cost much more a hundred bucks, are small and lightweight enough to easily install in a window when needed, and can be powered by even a very small generator.

you would be suprized at how great an open window with a box fan in it and a stand fan directly on you feels compared to having nothing to cool you, especialy after a big wicked storm that cools everything down.

I'd personally look at skipping the windows units and getting a free standing one. They have vent adapters that can go on a window to let the hot air out and you don't need to worry about hanging one.

For the other stuff it really comes down to what your stuff is and how you can get by. Having a gas or charcoal grill to cook on will allow you to just have to worry about running the fridge to keep food(or a gas oven). For heat in the winter a gas furnace will require a smaller generator to run then an electric one.

I have a 5500 watt right now. I can run my house on it although I wouldn't want to try to run the ac. With power out I use my propane grill as my oven isn't gas. Water heater is gas as well.

see this extensively documented how-to:
http://www.ar15.com/forums/t_10_17/644329_.html

ar-jedi

i think you need to answer some questions...

you have an electric, natgas, or oil furnace? can you heat the house to a reasonable temperature with just the fireplace?
you have an electric or gas-fired water heater?  how important is a hot shower during SHTF to you?
you have a well or city water supply?  if a well, how deep is it?
you have a sump pump which ejects water from the house?  how often does it run now, and during a storm?
you have a central A/C system, or individual window-mounted room A/C units?

ar-jedi

Much more expensive than window units of comparable cooling capacity. Also take up a lot more storage space.

Run your fuel numbers for cost to operate, and on hand storage quantities before getting set on a big unit.

Do this for for a two week outage. You'll find the cost of the unit isn't that big compared to what it will drink.

I've stripped my expectations down to a 2K unit running part time.
Refrigeration, cooking, & hot water are handled by my RV on propane.

I keep my old 4K 240V unit around solely for running the well pump, in case county water goes out too.

Typical gasoline consumption for a modern generator is 0.2 to 0.25 gallons per hour, for every 1,000 watts of power being produced (e.g., 0.4 to 0.5 gallons per hour when powering a 2 KW load).

Note that these figures only apply when the generator is powering a substantial load - The fuel efficiency drops off drastically when powering loads smaller than 10-20 percent of the generator's rated power output.

My theory is the same as the rest of these guys. Smaller generator, window unit AC. I figure I've still got enough power to rotate between the freezer and fridge, run a tv, etc.

I've got some portable propane heaters that I use to heat the main room of the house in the winter. Of course if you have gas central heat, you might get away with something less than an 8 amp load depending on what's in your house, but then you get into the whole issue of house wiring. Hence, I went with portable propane.

I'm still working out a plausible theory for the hot water heater. Thinking about tapping a single electric heating element (there's two on a hot water heater), hooking it to the genny, and let it heat the tank (albeit slower). Let it get hot or at least reasonably warm, and take a quick shower, or fill the bath tub. Then unhook it till you need hot water again. I've diagnosed/repaired water heaters with a failed element, they did continue to operate this way, they just didn't heat as well.

Microwave or propane/charcoal for cooking.

Thank you for all the info guys.  Based on the responses, I'm thinking a 5500 will work.  But here is some more info




Follow up question.  I'm looking at Generac and Briggs and Stratton models.  Are those brands you would recommend?

if you have access to natural gas, the conversion kits are a good investment...at the price of gasoline, they will pay for themselves pretty quickly... might check out US Carburetion Inc. and other sites for info

I use a squeeze bulb prime siphon feed line to run my Honda 3500w directly from a 5 gallon fuel can

Thank you.  I checked that site and see that I could buy a tri-fuel converstion kit and run it on gasoline, LP or natural gas.  My house has natural gas furnace and water heater.  I also have a line going out to the back yard for a gas grill.  I would assume I could use that line to feed the generatot.  Is that correct?  I'm not at all familiar with how the conversion kits work.

On your water heater, it only runs one element at a time.  Each element is 4500 watt (or maybe 5500 watt) but only one runs at a time.

With that info, you are definately going to be able to get by with a smaller generator.  One of the Champion inverter models would work perfectly....you would just have to spread out the use of it.

Both of those brands should have good parts availability for a long time - something that could be a problem with some of the Chinese-made brands.

Many of the Briggs & Stratton models are actually made by a division of Generac (formerly called Generac Portable Power) that B&S bought a few years ago. Most of the stuff that's still being sold under the Generac brand is made by ANOTHER division of Generac that WASN'T bought by B&S (confused yet? ).

Most of the models that both brands sell are conventional "synchronous" (non-inverter) designs, and tend to be a lot noisier than the inverter models made by Honda or Yamaha. As ColtRifle mentioned, Champion also makes a quiet inverter model that's cheaper than Honda or Yamaha's models, and has gotten good reviews.

I live in an area that lost power for almost 3 weeks the last time a major hurricane hit.  Never lost water or NG .  That being said My decision was to go with a permanent installed  NG generac  20kw.   I did get a lot of crap from some people on here when I posted for advice about going to big etc etc and I was wasting money or trying to live to normally .... etc etc .  But at the end of the day do what feels right for you.

I chose the 20kw for a few reasons listed below  (not in any particular order)

1. Was an aluminum body and not steel

2. Came with an auto transfer kit standard so I did not have to mix and match units

3. Came with a skirt kit standard

4. I had multiple companies come out and do a load analysis on my house and the consensus was I needed 16 to 17 kw to run the whole house. This included a safety margin of 15-20%+ depending on who did the analysis  My house was ALL electric  and I have a pool ( 30k water tank) .   I then looked at the gas consumption rates for NG ( you lose 10 % rated power on NG  vs propane ) based on the manufactures info  a 20 kw is really 18 kw . ( I also started converting my water heater  heating furnace and clothes dryer to NG . I also looked at what I would normally be running and based on the gas usage  I most likely would be running at 50 % load 90%+ of the time.   The fuel load of a 20 kw at 50% load is 206 CU.ft  this is less than the 17kw at a  full load of 261 CU.ft  and not much more than the 17kw at 50% load of 183CU.ft.  

5. Using the idea that an engine running at 50% will wear out slower than an engine running at 100%  I chose the larger unit.

6. I live in a VERY Hot and VERY humid climate , while I am single at the moment I do plan on starting a family and their safety and comfort will be a high priority.  Hence I am doing a lot of my work now while I can afford to. And I must admit that I would rather be as comfortable as possible for as long as possible.

7. Since installation I have turned on every single electrical appliance  motor etc etc etc ,  the generator essentially runs at 50%  when the whole house is wide open and only kicks it up momentarily when the compressors motors first  do a start up, then back to 50% run.

8.  I have the capability to put the appliances I put on NG back on electric if needed.

9.I live in a city that does not like storing of gas and  disallows any kind of propane tank ( outside the bbq size tanks )

10 The city I live in usually green lights all permits where the generator and switch are a matching unit with minimal red tape.

11. As I do live in  suburbia and there are noise ordinances and there is an HOA  the quiet test mode was welcomed on the applications.

12. If I ever decide to sell my house than I should recover on average 50% of my install costs.

13. I don't have to buy a large gas supply ,  As I said above  my area lost power for 3 weeks , that's a LOT of gas or propane !! but the NG I simply pay for what I use as I use it .

14. I cant begin to explain the warm and fuzzy feeling I get when that generator kicks on every week for the test run.  

15.  By doing much of the work myself  ( I did hire a licensed electrician and plumber to pull permits ) I paid less than  HALF what most companies wanted to charge for a turn key install.  


I do have to point out that since I have had the generator installed my area has NOT lost power in any way shape or form,    dammit !

Generator sizing guide

this is what happens!!!

question for you though –– what special provisions, if any, did you need to make on the gas line size and meter capacity in order to run the 20KW capacity genset?  do you have other natgas-fired equipment in the house (stove, water heater, etc)?

ar-jedi

I talked the local gas company into installing the gas line ,  My area was built in the late 70s early 80s and is ALL electrical.  gas company did the install for free. As I live in the city I had to get a permit to install the gas line, I ended up running all the gas lines at that time for the  furnace, water heater, clothes dryer and at the time what I thought would be a pool heater.  As devices wore out and needed replacing I installed NG versions instead of electrical. ( when I bought the house the previous owners told me after i signed  their averaged out billing for the electrical bill ran $700 a month !!!!  so I was freaking out ) gas meter installed and the regulator are standard size not the pay for upgrade size. I ran 1 inch black pipe to everything  . I hired a plumber to come out and he ran a vacuum test and then pulled the permit for the city. I decided that a generator was a better investment than a pool water heater and started working on that.  I did have a generator specialist run the gas consumption as some companies who wanted to sell me a turn key install said my regulator was to small and needed to be upgraded.  ( $$$$)  well long story short the calculations said I had a 17% percent chance of needing to upgrade if all my gas appliance were running at the same time  ( he sated this was using the worst case #'s from each appliance ).  again I live in a HOT and HUMID environment and have 30+ inches of insulation in the attic plus radiant,  I gambled that the odds of me firing off all my NG appliances ( furnace being the worst offender )  would  be in the 83 % side of the conclusions.  

After install I went and  ran the water heater and the clothes dryer and fired up the furnace and then kicked of the genny .... worked fine !!

In the future I would like to install a gas stove / oven unit when I redo the kitchen ,,, THAT may change everything and require an upgraded regulator.  


Ironically the  electrical company has come back and said they are doing a lot more genny installs in my area, and than I was the most knowledgeable person they have dealt with and that they now impress the clients when they do an install and use my knowledge to solve the issue.  The local city inspection official came out and  did an inspection and then asked me where to buy one  so he could install one. So we spent a good half hour discussing the steps I went through to make my decisions.

bjkb1f... US Carburetion has a calculation chart for diameter and length of supply lines...I would think that you are ok... do you have a way to lock up the generator at a distance from the house to reduce noise, and still keep it secure... in the 04/05 hurricane season down here, a lot of generators "walked"

I got a 15kw and I ru nthe whole house with out a hiccup like the utility is going on. You can get 15kw's rather cheaply, the only expensive part is if you want an auto or manual xfer switch. auto is nice, but if your still able bodied, manual all the way for pricing.

gettingstarted FWIW I think you did it exactly the right way for your situation.