Posted: 6/16/2010 6:26:21 PM EDT
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I'm looking to get a generator for our house and would love to hear some opinions.
First off, I'd like one big enough to power our entire house in the event of a temporary power outage; i.e., less than one week. We have 3,400 sf on our first and second levels, and another 1300 sf in the basement. I figure for the short term, I want to have all the comforts we normally have. For a longer term emergency, we would obviously be more judicious in our power consumption. I'm looking at Generac systems. We have natural gas, so I'm thinking the generator should run on natural gas rather than gasoline or diesel...and I'll have a backup 150 pound LP tank that will work by simply shutting off the natural gas valve and turning on the LP valve. 1. Is natural gas the best way to go? 2. Is having an LP backup a good idea or overkill? 3. What size unit is recommended for what I am describing? I'm looking at a 17kW and 20kW system and am wondering if that is way too much??? Before I divulge the price quotes on both units (which I have), I'd like to see if I'm on the right page to start. |
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20kW may be a bit light for running AC, etc.
natural gas is fine for a fuel, but you need to do more than just open a valve for propane. I would do what is needed to use propane as a backup, NG utilities rarely fail but it has happened. Be prepared for some heavy consumption of NG, it is nowhere near as energy dense as LP or liquid fuels. Ops |
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I've been looking into a very similar idea for my house. Some of my research so far has told me that any generator of that size should be water cooled. As far what size, that will depend on your needs. This Kohler website can be helpful. |
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I'll have a backup 150 pound LP tank The average generator uses around 0.25 gallons (or 1.06 pounds) of propane per hour, for every 1 KW of power produced. So, if your 20KW generator is running at half-power (i.e., 10 KW) it will go through your entire 150 pound supply in about 14 hours. EVERYBODY likes the idea of running their entire household on generator power...until they discover how much fuel it takes! 
Skibane's 80/20 Rule for Standby Power: Maintaining 80 percent of your normal standard of living during an emergency can be accomplished with a relatively small generator and modest fuel supply - but if you insist on also having the remaining 20 percent, it will cost you dearly. |
| LP and NG cannot be run through the same engine without some changes. The jets in the carb(not sure if they actually call them jets in a LP or NG setup?) would have to be changed, at the least. I'm not sure if any other changes would be required, since I don't have anything capable of running on LP or NG. |
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There is a TON of wisdom right there!!! EVERYBODY likes the idea of running their entire household on generator power...until they discover how much fuel it takes!
Skibane's 80/20 Rule for Standby Power: Maintaining 80 percent of your normal standard of living during an emergency can be accomplished with a relatively small generator and modest fuel supply - but if you insist on also having the remaining 20 percent, it will cost you dearly. 
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LP and NG cannot be run through the same engine without some changes. The jets in the carb(not sure if they actually call them jets in a LP or NG setup?) would have to be changed, at the least. I'm not sure if any other changes would be required, since I don't have anything capable of running on LP or NG. yea, LP and NAT gas dont work the same. NAT gas is in gas form and LP is coming through the pipe as a liquid. I dont have a LP engine, but lots of gas appliances, LP needs a larger orifice then NAT gas. I dont know if anyone makes a geny that can be quickly switched between the two. I would stick with gasoline or diesel. my experiance with furnaces is that LP and NG burn fuel alot faster then diesel. |
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I could be understanding this incorrectly, but I will essentially have two feed lines run into the generator...one is for NG, one is for LP. If NG fails, then I will have to close off that valve, and then open the valve for the LP. I am probably oversimplifying that, but that's how I understood it. The pipe fitter who is running the NG line for the generator is also the one who is setting up the LP backup. Sounds like I need to clarify and get a better understanding.
$7,300.00 for the 20kW unit installed with LP backup. $6,500.00 for the 17kW unit installed with LP backup. Are these prices reasonable? |
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Quoted: Quoted: There is a TON of wisdom right there!!! EVERYBODY likes the idea of running their entire household on generator power...until they discover how much fuel it takes! Skibane's 80/20 Rule for Standby Power: Maintaining 80 percent of your normal standard of living during an emergency can be accomplished with a relatively small generator and modest fuel supply - but if you insist on also having the remaining 20 percent, it will cost you dearly. This the correct answer. I bought a 5,500 watt genny before Y2K. It was cheap and I figured I could run almost the whole house minus the dryer. Later on I realized that this was silly. Why do I need to run the whole house, with the huge efficiency penalty that comes with such a large generator. Now I want to buy a 2000 watt Yamaha with the tri fuel kit. It will not run a lot at a time, but it will get everything done I absolutely need and is very, very fuel efficient. I can run the fridge for 4 hours, the freezer for 4 hours, while running other little stuff at the same time. I have plenty of battery powered lights so running the whole house at night is absolutely not even on the radar. Efficiency is everything. |
| I have an 8Kw LP guardian fully automated transfer switch self start etc. I went with Generac when I built my house as the electrical contractor I had is an authorized service provider. That said I would look at Kohler at least and some of the larger Briggs and Stratton units are worth a look too. Not sure I would choose the Generac again but it has not failed me in 14 years of service. It's louder than some and there is a pure sine wave issue that I changed out the inverter with a Xantrex to resolve. I think this issue doesn't exist anymore with the newer models. I don't think sq footage is how you want to determine what you need. Make a list of what you must have. 20Kw sounds to me like the kids watching their own dvd and computers in every room. Fuel consumption will be high for those conveniences. For me it was simple water, refrigeration and heat. The protected 100 amp sub panel powers the well, freezer(s) and fridge and keeps the fans running on the corn burner. I don't run the a/c on it but I live in WI and can live without it. I also have an alternate LV solar indoors lighting system so I don't need generator just for lights. I have only had a few extended runs but running my 8Kw at 60% used 10% of a 1000 gal lp tank in a 4 day straight run. I would think about a much smaller whole house unit with targeted must have circuits and take the money you save and spend it on an alternate fuel portable like a Honda eu2000i for running the absolute necessities economically. This also follows the 2 is 1 and 1 is none rule. Beyond all that I have a 15Kw portable PTO powered unit I bought at a farm sale for $300 that I can run off of my diesel tractor so technically I have 3 alternate fuel sources for electricity not counting solar. My intention for that was to power the workshop if necessary but have found it handy for taking the welder out in the boonies too.. |
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natural gas is fine for a fuel, but you need to do more than just open a valve for propane.
On the Generac systems, you can change from NG to LP with the flip of a switch. I've got the 10kw system hard wired in. 
LP and NG cannot be run through the same engine without some changes
Again, not true. Not only does my Generac run on either, my Honda 6500 runs on gas, NG and LP with the simple flip of a switch. |
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I got a 6,200 watt gen in 2005 - ordered it in the spring, it arrived in the fall - about 2 weeks before a hurricane arrived and produced a 2 day power outage! Quoted:
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There is a TON of wisdom right there!!! EVERYBODY likes the idea of running their entire household on generator power...until they discover how much fuel it takes!
Skibane's 80/20 Rule for Standby Power: Maintaining 80 percent of your normal standard of living during an emergency can be accomplished with a relatively small generator and modest fuel supply - but if you insist on also having the remaining 20 percent, it will cost you dearly.
This the correct answer. I bought a 5,500 watt genny before Y2K. It was cheap and I figured I could run almost the whole house minus the dryer. Later on I realized that this was silly. Why do I need to run the whole house, with the huge efficiency penalty that comes with such a large generator. Now I want to buy a 2000 watt Yamaha with the tri fuel kit. It will not run a lot at a time, but it will get everything done I absolutely need and is very, very fuel efficient. I can run the fridge for 4 hours, the freezer for 4 hours, while running other little stuff at the same time. I have plenty of battery powered lights so running the whole house at night is absolutely not even on the radar. Efficiency is everything. For my purposes, I think 6.2kW is the perfect size. I have 2 central a/c units and 2 water heaters - all medium-large electric loads. My gen size allows me to run one of the a/c units - nice to be able to retreat to a part of the house that is cool (in Florida in the summer). It also allows me to run water heaters - I run 1 at a time for about 1 hour. In power outages, I run 1 water heater for 1 hour one day and alternate heating one each day thereafter - this is enough to give me some warm water almost all the time- I like showers that are not cold (call me a wuss)...
I specifically chose my gen size knowing what loads I had and which I wanted to run... My main consideration was that I wanted a gen large enough to run at least 1 water heater (4,500 watts / 240V) with some watts to spare. A 6.2 kW gen also allows me to start and run my smaller (1 ton) central a/c unit. If I didn't have water heaters and a/c units to consider, I could easily get by with one of the 2 to 3 kW inverter gens... In terms of the OP - for the $ spent, I would rather have redundency that size - i.e. I would rather have 2 or 3 smaller generators than 1 large one. I think NG is a good choice if you have NG in your neighborhood (I don't  )... and with the smaller gens, 150 to 300 pounds of LP would be very adequate for the vast majority of outages...
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natural gas is fine for a fuel, but you need to do more than just open a valve for propane.
On the Generac systems, you can change from NG to LP with the flip of a switch. I've got the 10kw system hard wired in. http://i47.tinypic.com/zlpua1.jpg LP and NG cannot be run through the same engine without some changes
Again, not true. Not only does my Generac run on either, my Honda 6500 runs on gas, NG and LP with the simple flip of a switch. Most generators will not be set up that way, in all probability. I don't know for certain because I don't have, or really want, a LP/NG genset. The jet/orifice size will NOT be the same for both fuels, thus whatever quick switch your genset has, it's changing the jet/orifice from larger to smaller or vice versa. Most conversions that I know of involve rendering the carb useless for gasoline after the conversion is done, meaning you'd have to purchase another carb to run gasoline again. One other problem with running LP or NG through an engine designed for gasoline is that it will dry out the gaskets and seals...so you end up with vacuum leaks in the intake system...not to mention a 10-30% power loss(from what data I've found so far) compared to running that engine on gas. The first part I know from talking to people around here that had LP conversions done on their gasoline vehicles. In any case, you still have to change something to change fuels. 
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| After giving it some more thought, I may consider going with a smaller, more efficient unit, and just back-up the basement. We would not have to heat or cool it, we have plenty of space down there, and it would cost a lot less. AND, I could have another portable unit and still come out for far less $. Thanks for all the replies. |
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I could be understanding this incorrectly, but I will essentially have two feed lines run into the generator...one is for NG, one is for LP. If NG fails, then I will have to close off that valve, and then open the valve for the LP. I am probably oversimplifying that, but that's how I understood it. The pipe fitter who is running the NG line for the generator is also the one who is setting up the LP backup. Sounds like I need to clarify and get a better understanding. $7,300.00 for the 20kW unit installed with LP backup. $6,500.00 for the 17kW unit installed with LP backup. Are these prices reasonable? What companies were you getting those quotes from? Been searching for generator install companies myself. I have a 1600 sqft house that I would like to get a LP standby generator from and have been looking at these ones at home depot. I'm undecided between the Kohler 12kw and the GE 12kw. I also need to buy an LP tank. Need to run the well pump, fridge, some lights, ceiling fans, hot water heater, and maybe AC. House is all electric except for a gas fireplace. Currently don't have the fireplace hooked up. |
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After giving it some more thought, I may consider going with a smaller, more efficient unit, and just back-up the basement. We would not have to heat or cool it, we have plenty of space down there, and it would cost a lot less. AND, I could have another portable unit and still come out for far less $. Thanks for all the replies. I like the idea of having a good-quality small portable generator for extended running, along with a cheap, larger portable generator for occasional use. This approach gives you good fuel economy and minimal noise when powering small loads, yet doesn't leave you without the ability to power big loads when necessary. And, it gives you a spare generator to loan out to your relatives or use as a backup if the other one dies. |
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Good choice me thinks, I have a similar sized house (No AC needed in Maine) and get by pretty well with a 5.5/8.5KW gas generator. (need to run 220 well and septic pumps mostly) I could go maybe a week on intermittant use and only 10 gals of gas.
Someday I'd like to have a larger genny but I'd like it to run off a PTO from a diesel tractor. Quoted:
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After giving it some more thought, I may consider going with a smaller, more efficient unit, and just back-up the basement. We would not have to heat or cool it, we have plenty of space down there, and it would cost a lot less. AND, I could have another portable unit and still come out for far less $. Thanks for all the replies. I like the idea of having a good-quality small portable generator for extended running, along with a cheap, larger portable generator for occasional use. This approach gives you good fuel economy and minimal noise when powering small loads, yet doesn't leave you without the ability to power big loads when necessary. And, it gives you a spare generator to loan out to your relatives or use as a backup if the other one dies. Posted Via AR15.Com Mobile |
| I bought a 10K head and made a mount to hook it up to the PTO on my tractor. I've got around $600 in it. It will run everything in my house. Just not all at the same time. If I want to run the dryer or AC I'm gonna need to turn some other stuff off. Knock on wood...the power outages are few and far between anymore and rarely last more than a half hour to an hour. It is just enough hassle to hook up that I don't bother with it for the nuisance outages but it is comforting to know that it is available if there were some major catastrophe. |
| I have a 4400 watt Homelite genny and during outages I can run most but not all of my home using this unit. In retrospect, I wish that I had gotten a 6000-8000 watt unit so that I wouldn't have had to be so careful about what I turned on and when in my home. I also want to put in a disconnect swich instead of pulling extension cords throughout the house. However, when my generator is running, my home seems like a resort compared to the rest of my neighborhood. Unfortunately, during extended outages neighbors begin coming to my home for charging cell phones, gettig ice and for entertaining their kids. |
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Quoted: Quoted: After giving it some more thought, I may consider going with a smaller, more efficient unit, and just back-up the basement. We would not have to heat or cool it, we have plenty of space down there, and it would cost a lot less. AND, I could have another portable unit and still come out for far less $. Thanks for all the replies. I like the idea of having a good-quality small portable generator for extended running, along with a cheap, larger portable generator for occasional use. This approach gives you good fuel economy and minimal noise when powering small loads, yet doesn't leave you without the ability to power big loads when necessary. And, it gives you a spare generator to loan out to your relatives or use as a backup if the other one dies. This is exactly what I have. I bought a cheap 5.5kw a long time ago. I just bought a 800w harbor freight generator for running small loads and plan on buying a nice Yamaha 2000W genny for long term use. I keep the wire on hand to rewire my well pump to run with my big generator. It does not have to run all the time and we have propane water heater. The yamaha will run a freezer and my battery chargers at the same time. It will run lights and the frigerator at the same time. A little bit of planning and I can run just enough to keep what I need running. I am not planning on depending on the harbor freight genny, but it may end up being a good addition. |
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I'm looking to get a generator for our house and would love to hear some opinions. i see you live in TN. rural? do you have a tractor with a PTO? the backup power route i went for my situation was to have a small, gas-sipping Honda inverter (EU2000i) for most of the typical household needs (keep fridge/freezer cold, etc), and have a larger PTO-powered generator (Tiger PTO10) for infrequent needs like the A/C and the deep well pump. this way i get the best of both worlds in terms of backup options, fuel-consumption minimization, and noise. my PTO generator head is the same as shown below, but instead of being on a pull-behind cart it is on a 3pt "sled". it takes a couple of minutes to hook the 3pt hitch and PTO shaft up to the tractor, but once in place you can provide a lot of power to the house. of course the tractor+PTO generator setup consumes more fuel (in this case diesel) than the small generator –– and produces more noise –– so i only use it for "on-demand" big loads. one other nice thing about this is portability. while i don't anticipate bugging out of my house to a nearby location, it's always an option to bring the tractor and generator along (e.g., to my brother's house a couple of miles away). and finally, since the PTO generator has no engine, it is one less thing to maintain. if the tractor engine runs (it's a Kubota, it ALWAYS runs!) the generator head will make power. in general, you will want approximately 2 PTO HP for each KW output –– note that that is PTO HP, not engine HP. for gear-driven PTO's, deduct about 10% from the engine HP. for HST-driven (hydrostatic) PTO's, deduct about 20% from the engine HP. 
ar-jedi ps: note that some folks simply mount the generator inside a structure like a shed, back the tractor against the structure, and then run the PTO shaft through a small access panel in the wall... 
and of course you can run it out in the field... 
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I have 2- Porter Cable 2500W with honda engine, 1-Master 65000W with13 HP honda. Around 800 Ah of AGM batteriesand chargers.
Blake, lowes sells Kolher and Generac. I would go with Kohler. I install and work on generators. My plan is to buy a Honda or Yamaha 2000-2500 inverter generator and not look back. With a small gas sipper, two mid range ones for back up, and 1 large one I feel okay. I have acess to many more generators if needed.
I really need to upgrade the small 6K BTU window shaker I keep for summer outages. Would like a 10-18K btu to try and cool more area. No way am Igoing to try and run the 5 ton house unit. Simply not cost effective. OP, if you need help and are close to West TN, let me know.(TN lic. electrical contractor) |