backup generators are very expensive.... isn't it cheaper to install solar?

Nope  :)

But that is what I did anyway.  I figured if I spent $10k to install a nice automated transfer generator system I might as well stick that money in solar panels, inverter and batteries.  I am often asked what my payback is on my solar panels; I say they paid for themselves on our first power outage last spring.  The I ask what is the payback on a nice auto transfer genset, the same or ?

I figured I would have to maintain a genset, exercise it, make sure everything is working all the time or just get a solar setup and use it every day.  I know it works, the grid is shut off at our house every day when we hit "on peak" electric rates and then almost everything is run from solar or if needed the batteries.

Both a genset and our solar setup require regular maintenance to keep them working, at least I get something back from our solar setup, about $50 a month worth of free electricity.  The genset would be $0 and actually cost me monthly to exercise it and cost when it was doing what I bought it to do.

There are pro’s and con’s to both sides and every situation is different.  In some cases a genset makes more sense in other solar might be the way to go.

last generator I priced up for a client was around $70K making solar far cheaper after all the rebates!

It's somewhere between a stunt and a proof of concept, but a curve ball worthy of discussion:

Hybrid car w/ inverter vs stand alone generator.

There were several accounts of people running their emergency systems off their Toyota Prius in the New England ice storm last year. You certainly can't run a house off one, but an emergency circuit of a refrigerator/freezer, television, lights and boiler should be possible. This guy claimed 5 gallons of gas for three days, and if true, that's tiny: Tech-Savvy Prius Owner Uses Hybrid To Power House During Snow Storm

Advantages: PZEV emissions, motor only runs to recharge the battery bank and then shuts off, you get a car to drive around in the rest of time and to go get more gas unlike a generator that sits around doing nothing most of the time, very quiet, extremely low fuel use.

Disadvantages: very little power supplied compared to a real generator, not its intended purpose (warrantee issues?), sure better not keep the car in the garage when trying this trick. I'm sure there are others, discuss...

I think he is on to something; imagine if there was an electric hybrid that was designed to be used for back-up power. I'm buying stock in that company.

DaveS

A stock car alternator will put out about 750w at idle. So if you have a 1200-1500w inverter and an idling car you can run just about any single item that you can plug in, more if they don't draw a lot.

In our system we have approx 500 amps at 48 volts or 24kwh of battery power. We choose not to purchase a separate genset instead using an idling car and an inverter in a pinch. As Dave noted when the power is out the sun is likely not shining. So what I do is attach a 1750w inverter to the idling car, that inverter feeds an iota 15 amp 48 volt battery charger that is attached to our battery bank. Then the main house inverter (Xantrex XW 6048) inverter uses power from the battery bank to supply power around the house. Our Toyota mini-van has an 80 ah alternator and at idle can supply about 700w, if I bump up the idle it will power our charger just fine, but at that point the van is consuming about .4 gallons per hour. Our VW diesel on the other hand has a 120 amp alt, and can supply the full 900 watts needed for the charger at idle and consumes about .15 gallons of diesel or bio-diesel an hour, definitely the way to go in an extended outage.

So the short of it, an idling car and good sized inverter will supply quite a bit of power. And the car engine, even gas, will likely be more efficient than a straight out gas genset unless the genset is inverter based and can idle down as load dictates. Along those same lines an idling car is most likely quieter and might draw less attention than a loud genset.

Obviously there are disadvantages; the car has to be well ventilated and somehow secure.