If you look around, you find that you can get 5000 watt portable generators for around $500.00 or so. Stepping up to 1 10000 watt generator costs around $1500.00 or so. This leads to the question:
Can you safley connect two 5000 watt portable generators to get 10000 watts of power?
Yes, the two separate genarators will supply 10,000 Watts. This is basically the same thing that the power companies do, multiple genarators supply the grid. The reason a bigger genarator may cost more could be that it is more effienct to run the larger one by itself than two small ones, thus saving money in the long run. Maintance on two genarators may cost you twice as much, meaning a larger expense in the long run. The bigger genarator may only be a bit larger than one of the smaller ones, thus saving floor space.
I took my Engineering Economics class in college from a guy at AEP and he used a lot of real world capital expenditure and amortimazation examples from actual power company senarios. You’d be dumbfounded to learn how complicated it is to determine how much power to produce while minimizing lost. I know I was. 
No.
If you don’t have a synchroscope, just connecting the two generators together is going to be difficult to do without damaging something.
Additionally, if there isn’t any load sharing mechanism, you could easily end up with a situation where one generator is trying to supply 7500 watts and the other is only trying to supply 2500 watts. The first one burns out under the load, and the second one tries to supply the entire 10,000 watts (plus maybe some additional power trying to turn what is left of the first generator) and it also burns up.
Opps, I was so worried about cost I forget to address saftey. :smack: Thanks, Engineer_Comp_Geek.
What Mr e. c. geek said. You can’t just chain generators together like batteries, they have to be running in phase or you’ll get one “pushing” while the other is “pulling” in the AC cycle and the result would be interesting.
However on boats what is typical in some configurations is to have each power source feed a different panel or load.
With two Gensets one could supply lighting and the like and other maybe a heater of furnace blower or loads that you don’t need all the time.
The other thing if you are thinking of hooking up to a house is transfer switching, not only is it not prudent to try and hook two generators up together it is not very smart to try and hook a generator or other AC generating device up to household power with out having a switch between the two, if not you will get the total sensory experience. Some of the generators sold for backup home power are setup with an automatic transfer switch, if the switch senses that power from the grid is not available it will automaticlly switch to the alternate source, in this case the Generator.
**SOME ** generators can be lashed together to provide roughly double the power of one without damaging anything.
About the only ones I can think of offhand are those little red ultra-quiet Honda jobbies. Honda makes a device that links two generators in parallel and keeps them in synch. This works because these models produce DC internally, then run it through an inverter to create the AC power, and it’s relatively trivial to sync two DC-fed inverters than it is to sync two engine-driven alternators.
I like this. It made me smile*. I heard a primary transformer explosion at a 225MW plant described similarly.
[sub]* (Of course, seeing a Member named Small Clanger made me smile too…)[/sub]
The cheapest, and easier way to do this, is to back feed one generator directly to the panel. Using an interlock kit would make this legal. This would enable u to power anything in the panel, or in the house with the first generator. Then, what you can do is select what circuits you would want the second generator to run, and install those circuits on a manual transfer switch so they can be switched off the panel, and run by a second independent generator all by themselves. This would be a good way to be able to use your central air and powering it with it own generator.
If it were me, id get a 3500-5000 watt generator for the entire house, and use that to back feed the panel. Then id get a 7500 watt Gen just for the central air, and hook that no to a small manual transfer kit. This way hour not running a 10,000-12,000 watt generator at times u don’t need to run a central air unit and the small 3500 watt Gen is enough for ererything else