Onan 45KW, runs on propane. Automatic start/transfer.
Liquid cool. Very happy with it. Cycle it once a month, run block heater in the winter and cooler seasons.
It's a 300 cu inch 6 cylinder engine, but has an oversized radiator and fan. In general, if you can place the unit away from bedrooms you're OK. If you have a power failure, but your generator is keeping your heating/cooling going, you'll sleep much better than being powerless and uncomfortable. The noise will soon sound very sweet. If it's close enough that it would bother your neighbors, move further out into the country or buy and extra 5 KW and burry a line and outlet near the property line they can use.
Generator unit cost about $17K now, xfer switch (400A) was about $3500, 200A switch is about $2500. Installed myself, 1st at old house then at current house. About $3700 for wire, conduit, disconnect, pad, propane tank. Rule of thumb is install cost = 2-3X generator and transfer switch cost if contracted out.
Other comments:
In a retrofit, in many ways the generator is the cheapest part of the deal. Theres a lot of electrical work to do for the transfer switch. Local codes will probably want a disconnect in the same area as the breaker boxes. Then there's all the digging, generator pad, getting fuel there, etc.
When thinking about size, consider putting a new breaker panel before the transfer switch. I did this and put the big 10KW resistive electric heater strips for the heat pumps on that new panel. This depends a lot on your loads. A house with all gas appliances probably won't need this. In an all electric house (what I have) you could also put things like the oven before the generator to decrease the generator size and cost. If you do an outbuilding, you can put the welder before the generator and run a smaller circuit out on the generator for lights and a small outlet. Also price out the full ranges of generators. There may be a small difference between a 12 and 15KW unit because they both use the same 3 cylinder engine. But at 20KW there might be a jump because you need a 4 cylinder engine, but then there would be a much smaller jump to go to 25KW which would still be the 4 cylinder engine. Unfortunately, the mad disease that affect managers and marketing is changing this as we live in a world where things are price by silly perceptions and nothing that relates to cost.
On the topic of fuel consumption, I could never get anyone to give me estimates on how much propane the generator would use. Here is where that landed. Think about any vehicle with a similar sized engine. Think about how much gasoline it would use going down the road at 55 mph. That's about how many gallons per hour your generator will use on a typical load. For my 300 cu inch engine, it runs 1 gallon per hour with no load, 2 gallons per hour typical, and can go up to 3-4 gallons per hour at a big load (30 KW or so). So for me, I plan on 2.5 gallons per hour. Propane companies here make you buy the tank for standby use. Up side is anyone can fill it because you own it. Remember that it's not when you run out of fuel, it's when are conditions such that a propane truck can come down the driveway.
While you're digging up the world, consider running a copper line to the deck so you can stop buying bottles of propane/natural gas for the grill.
The 15kw Generacs are very popular, and there are benefits to dealers that are used to installing and working on them. Again the panel before the xfer switch can really help balance things out. The ratings on the Generacs are a peak rating, for a small amount of time, but that's OK since you just need that peak to get compressors spinning (be it refrigerators or freon). There are also air cooled units which are more noise less maintenance. Enclosure rust is a big problem, aluminum would be worth it if you can get it. As always, listen to kennyd.
techman's fuel comments are right on the money.
So start by popping off the cover to your breaker panel and figure out what things draw. If you are not comfortable doing this, then just contract out the entire process and whoever is doing it all will help you with the sizing.
This is a lot like buying a tractor. Start with defining your needs (the hard part), then figure out logistics (where will things live, how do you prepare the area for them), and finally the fun and easy part, how much power do you want to buy. Starting out saying "I need a xxKW generator" is as silly as starting out saying "I need a 40 HP tractor". That step is the _end_ of the process, not the beginning.
Finally, there are many spousal brownie points to be had to a fully automatic system if you can swing it. And if you go portable generator and manual transfer of a few circuit, still put in a 2.5 or 3" conduit from the outside where you'll be parking the generator for when you want to upgrade in the future. Be sure to include a 2nd smaller conduit for the low voltage control circuits need in a fully automatic system.
Pete
