As far as I'm concerned there are two brands worth consideration. Any good Onan or Kohler dealer will survey your house and tell you what size generator you need as part of the selling process. The info you have supplied so far is not enough to determine what size gen-set you need. There are other brands of "home sized" generators such as Generac, Briggs and Stratton and so on available, but I wouldn't install one at my house.

You'll need to do a load calculation before you do anything.

Keep in mind, if you are under the 2008 NEC there is a pesky new code that requires that an automatic standby generator be capable of carry the WHOLE transferred load unless a load management system is in place. This can be upwards of 35-40kW.

Hi,

I have a Cummins Onan RS 20,000 generator which is now three years old. I purchased it at Costco and had it professionally installed. Total time it took from start to finish is about 2 months. I also needed planning an permits from my local town. I live in New York State.

The generator has been very reliable, and I change the oil myself. Cost wise to install / purchase / propane tank, trenching etc. was about $US 18,000.

If you look back at my posts I have commented a few times on my generator experiences. I think what puts people off is the cost.

The two most difficult requirments on your list are:

1) Koi pond pumps. These in themselves require only a little electricity. However I presume any outage longer than say six hours will kill your fish. So this precludes you having any manual start generator. You need auto start. Most generators do have this feature which are propane powered. However petrol generators are not the way to go unfortunately, because these are often the cheapest option.

2) Air conditioning. I am assuming you want to run the central home A/C. Again the A/C itself when running is not too bad. What is difficult is the surge currents on the A/C compressor start up. That surge current requires a decent generator which can handle that power spike demand. Some people get around this issue by not trying to run central A/C off a generator. Instead they have one room equiped with a smaller window installed generator. When the power goes out they hold-up in that one room for a few days untill power is restored.

As I see it I would go for Kohler or Cummins Onan. They are the best and most reliable, but costly. If you want a small window A/C installation, you can probablly go for a 12 Kw sized generator. If you want whole house A/C you need at least a 20 kw generator.

Note that there is a large price different between a 12 kw installation and a 20 kw installation. Why? A 12 kw installation is based on two cylinder lawn mower engines, do not need a poured concrete pad and can be lifted into place by dour men. 20 kw generators are in the 1200 lbs weight range. Need concrete pads and a crane / back hoe / heavy lift to install. Therefore a 12 kw installation all in may be about $US 10,000 and a 20kw installation twice that.

Propane is also good in that it will store indefinately. Diesel and petrol degrade over time. You can usually tell a good generator by weight. Heavier is better. Why? More copper in the windings, cast iron engine, heavier housing. Most 20 kw generators are car / truck engine basedm water cooled and run at 1,800 rpm. Cheaper 12 kw generators run at 3,600 rpm, make more noise and wear out faster. But are cheaper.

One finaly thing to note. I did have a few issues on installation with my Cummins Onan generator. However the Cummins Onan follow up service is really good. Top notch. They came out three times to visit. All free of charge. I paid for them to come out one time on generator turn on and was impressed by their service.

Costco is the cheapest place I know to buy Onan. However Costco service is junk in this reguard. If you do have an issue the trick is to get Costco to give you their Cummins Onan service-tie-in rep. Once you get hold of that person you are all set.

One final note, remember to have lightning and surge protection also to be installed. You do not want a bad storm to zap all that generator capacity.

Good luck Mike.

Here is a link that might be useful: Costco Cummins Onan Generator

to add to the excellent advice above, make SURE that the people who do the install are certified by the manufacturer to install and do initial startup. i have seen electricians who have never done gensets before really screw up stuff. it is not as simple as hooking up a few wires and running the fuel supply to it.

I believe the natural gas/propane ones are probably kind of interchangeable, it would be cool if you could have one that did both.

I think the issue of fuel freshness is a HUGE one - gasoline (I doubt you could legally store gasoline in the sort of quantity you might need, which would make diesel more appropriate) and diesel definitely have a limited shelf life, you can have the diesel tested, but I guess the best thing is to use it up in something else - if it's special diesel - dyed - not for road use it may not be legal to use it up in a truck. The people who supply the fuel must have some option for fuel rotation, since anyone with a backup generator would be in the same boat.

For those reasons I would go with propane or natural gas with a propane backup option if one exists.

Since you are in Southern Louisiana, for reasons political and geographical, I suspect you need bigger/more fuel capacity since weather issues might mean you'd be on your own for longer. Natural gas supplies could easily be affected so storage propane may be the best bet.

Thanks for all the suggestions.

The generator will be propane and we'll have a 250 gallon storage tank. Being without power for 3 months after Katrina was not fun.

We'll have to discuss with the dealer about the start up issue but it seems pretty unanimous that Onan and Kohler are the way to go.

I'll check into the prices and size I need.

Pretty funny typo, " dour men".

We do many generator installs.
250 gallon for a whole house in the 20-30kW range is just not large enough.
500 minimum/1000 preferred.
Remember, you will be burning a couple of gallons every week during the exercise cycle and 3-6 gallons per hour during an outage depending on the load imposed on the genset.
The tanks are only filled to 80% capacity to allow vapor to form so your 250 gallon tank only holds about 200 gallons.

"Being without power for 3 months after Katrina was not fun."

Boy, that puts things into perspective for me. I suspect 250 gallons may not be enough, considering that if things are bad again, it might take a long time to get a refill.

Still, better than nothing, and you can always ration yourself, I guess it's possible to switch on and off when you need it.

I had a laugh at 'dour men' too, perhaps they need to cheer up!

yeah the county here has 2 30Kw kohlers at their tower sites. their 500 gallon tanks only last a few days, but then again they pretty much run the gennies at 3/4 load 24/7 when they are needed.

i would get as large a tank as you can get. if your supplier only does 250 gallon tanks, have them put 2-3 of them together. this way you maybe only have to get LP delivered 1x a week during extended outages.

best bet is to run the genny long enough to cool down teh house, fridge, and if applicable deepfreeze, then shut it off for a while. you can extend a tank of LP for a long time if you don't try to run the genny 24/7. a fridge or freezer will stay near temp for 6-8 hours IF they are full even longer. if you do have an extended outage, put jugs of water in them to get them as full as possible. then leave them closed unless necessary. the frozen/cold water will help keep each at temp and allow for longer times between needed to run.

Unless you are very well off, fuel cost will be a significant concern if you use a propane genset for very long. At say $6/hour, a week of intermittent use (half of the time) would consume about 250 gallons, costing $500 in fuel alone. Most gensets will need an oil/filter change in that time frame too.

The expense of running a propane set for 3 months even intermittently would make me think strongly about a diesel set. You can get about 12Kwh/gallon from a diesel set in the size under consideration, and you can carry diesel fuel in a bucket if you have to.

wayne440,
I agree.
I always try to push customers toward diesel unless the situation is totally inpractical.
With a good sized belly tank, you can save thousands on the installation and fuel cost as well as maintenance.

Ok, fine re the diesel, but 1) how many of the diesel ones are silence enough to be permitted in a suburban situation (or not drive the owners insane)?

Having worked in the film industry, I know how quiet a diesel generator CAN be, but how much soundproofing goes into a domestic unit?

Next question is fuel storage, environmental laws are pretty tough about fuel oil tanks now, can they be below ground and how much does that add to the cost, if above ground, what issues does that raise apart from the aesthetics (although propane ain't going to be that pretty either)

LASTLY, and can someone *please* answer this one for me, what happens with the fuel when it ages? It has to be used up or replaced periodically. How does that work?

A diesel will be louder than a comparable size propane unit unless you spend lots of $$ for a 'silenced' unit. Having said this, the sound of my 80's vintage plain vanilla diesel is not at all objectionable to me, compared to the silence of a powerless, uncomfortably hot or cold house- and many new diesel gensets are noticeably quieter than mine. I don't know about 'permits' or your subdivision, my property belongs to me and I pretty much do what I want on it, no one has voiced an objection yet.

A sub-base tank is the usual way to set up fuel storage in my area. It is a square box that the genset sits on top of. Not real pretty, but propane tanks are not art items either. Once again, either looks good compared to sitting in the dark.

There are many references to proper fuel storage on the internet. Properly stored, diesel fuel will store 20 years or more. Improperly stored diesel can go bad in weeks. I have used fuel that I know was 15 years old with no trouble.

1) Because of laws pertaining to noise emission, most diesels are built to the same or better specs than many propane units. We sell a line of diesels here in Florida that are in most cases rated quieter than the propanes from the same company.
2) You can get as much soundproofing or as little as you want as long as the unit meets local requirements.
3) Don't even consider an underground storage tank. The permitting and the liability would be too much. The manufacturers can supply a double wall tank that will meet all requirements without having to build containment dikes, etc.
4) Modern fuels will last for a long time. Keep in mind that the gen will be exercising every week and will require a little bit of fuel to be added every few months. If you want, don't fill the tank all the way up until hurricane season arrives. Any outage in between should be of rather short duration.

I'm not concerned about the noise. Our house is out in the country on 7 acres. The closest neighbor is across the road and about 10 acres away. When you're without power, no one cares about the noise anyway. When the power came back on, it was eerily silent after listening to them run for 3 months after Katrina. LOL

We're now considering building a genny to run off our tractor's PTO. It's very fuel efficient.

Before we came back after Katrina, we bought 2, 100 gallon gas tanks so if we have to, we can fill them up with diesel. Lessons learned after Katrina. You can't store enough fuel to keep you going till the power comes back on after a big storm. We had to travel 100 miles weekly to get fuel during those 3 months.

I have a PTO set as well, it is probably 30 years old. If you are comfortable with having your tractor run unattended, they are worth consideration. If your tractor doesn't run, someone will have one that does.

We have several tractors. My son is a Master ASE Diesel Mechanic and a genius when it comes to motors. He's built several PTO gennys and said he could build one for a couple of thousand $$. That's much cheaper than buying a generator.

Thanks for the info. I haven't ever seen a domestic diesel unit so I had no idea of how they're set up. I am in an urban/suburban area, so I'm referring to issues where your neighbour's wall is 10' away.

I like the tractor/pto idea if you have the room and setup, if you have an engine problem, hook up another tractor. If the generator side was cheap, I guess you can put in a cheaper old tractor for that matter....

I actually travelled up a river on a tourist cruise 'ship' (not that big) which was powered by two tractors, wheel-less and bolted in place. No marinisation either, they were water cooled with radiator etc as standard, and the air in the engine room was just well-ventilated with fans etc (exhausts were piped out of course)

Hi,

I did not realize you had tractors around. If that is the case PTO off a tractor is a good solution. My only recomendation is to spend a few dollars on some fuel stabilizer. This is an additive that you add to fuel to keep it fresh. I use stabil for my lawn mower. Stabil will keep fresh fuel fresh from between one to two years. What it is is a bactericide which kills of bugs. Note it will not however restore old fuel.

There are other stabilizers / restores for diesel fuel like PRI-D. However I have had no experience with that one.

Diesel fuel will also gel in cold temperatures, however you being that far south I think is not going to be an issue.

All the best, Mike.