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Standby Generator Question

Posted by NaplesGuy (My Page) on
Mon, Mar 12, 12 at 20:07

I'm building a home in Naples, Fl and I was looking at installing a standby generator.

My electrical contractor recommended a Generac 25KW liquid-cooled unit. With all parts and installation, it is an expensive undertaking (about $18K). I inquired about smaller units, but he said that he doesn't recommend them. he said the smaller units, which are air cooled, are not as reliable and do not provide well regulated voltage (he said the actual sine wave is screwed up). The end result is that using the generator will end up frying sensitive electronics such as TVs or computers.

Does all of this sound right? Am I being steered in the right direction? Thanks.

Follow-Up Postings:

RE: Standby Generator Question

I think there are many smaller generators with clean power. If that's a major concern, get an inverter generator.

I've never had experience with Generacs, but I've seen many posts on many boards about them letting people down in emergencies.

RE: Standby Generator Question

Some people call them genercrap.

RE: Standby Generator Question

Just in case you don't have the basics yet, if the generator is going to transfer automatically an run the whole house and transfer , you need to be above a certain size to satisfy the newest NEC. If you want smaller, you have to go manual transfer or install a transfer panel to power selected circuits that match generator output.

RE: Standby Generator Question


Your electical contractor is correct. He is recomending a top of the line solution and as you have found out, it is expensive.

If you have sensitive electronics then what he recomends is best. A cheaper solution for sensitive electronics is something like a Honda 6500 petrol genset. This has power inverter electronics and does produce a very clean well controlled power waveform. However it is only 6.5 kw output.

If your contractor is recommeding 25kw, then your home is quite large. I think his recommendation is based on the total power that you will require rather than anything else. I noticed that you are in Florida. So I suspect that he is sizing the generator set for Air Conditioning units. Air Conditioning, in particular the compressors need alot of current to start up and power to run. Any genset over 17Kw is pretty much a water cooled unit, based on a car engine of some sort. These units are heavy and need a crane or some sort of heavy lift to install.

If you can get your power requirements down to below 12kw-15kw, then a air cooled unit would be possible. These are lawn mower engine based. The main advantage of the air cooled units is that the total cost would be maybe 1/2 that of the water colled unit. *BUT* it would probablly mean your air conditioning would not be functional in a power outage.

Generac do have a bad reputation. I think mainly from the really bad units they sold at Lowes and Home Depot. They also make some higher end units, and I think the the unit that your contractor recommends is in this category.

I installed a 20kw Cummins Onan genset 5 years ago. The total cost all in was about $US 20k. This includes a 500 gallon propane tank, trenching, heavy lift of genset at install and rewiring for transfer switch and circuits. I actually bought my Cummins Onan genset from Costco. You can check out their web site for pricing.

I think that genset brand wise Cummins Onan is best (I am a bit biased on this). Cummins Onan are typically the units used at airports, hospitals and prisons. We also have three container sized units at work. Other good brands are (a) Kohler and (b) Ingersoll Rand. These brands are also quite expensive.

I think your contractor is not nessesarily incorrect in his recomendation. A cheaper solution is possible so long as you understand what the system may not be able to do and you are happy with it. One thing people do is to also buy a cheap window air conditioner. The using this temporarily to have one room air conditioned during a black out. Doing this they can cut the power requirements down, and hence have a smaller genset.

Hope this is useful.

All the best, Mike.

RE: Standby Generator Question


The price your contractor is quoting is not unresonable for that particular setup. With that being said, I am not a big fan of Generac. Down there in hurricane country, your generator might be required to run continously for several weeks after a hurricane. That consumer grade generac may or may not be up the task.

Be aware that with an automatic transfer switch, it is now required by code that the generator must be large enough to run ALL loads that are connected to it. This is in the event that you are away from home when power is lost with everything runing. If you choose a manual transfer switch, you can use a smaller generator because it is expected that you will turn off unnecessary loads before manually switching to generator power. The manual switch is also somewhat cheaper.

Onan, Kohler and Cat are just a few brands with good reputations. Whatever brand you coose, I would definately go with a liquid cooled, automotive style engine.

I would also look at Taylor Generators. They make a great generator with quality components at a resonalkbe price over in Mississippi. If you do go with Generac, look at thier Quietsource line. Its a better unit with an Aluminium enclosure that wont rust.

RE: Standby Generator Question

I've got an 80 KVA generac on an automatic switch. That's way overkill (but it could take the whole 400A service). In fact, the average load is only about 6KVA (and that's almost a total electric house...only thing that's on the propane is the cooktops and the tankless water heater).

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