A 120 VAC (rms) sine wave is almost 170 volts peak to peak.  RMS is a measure of the "area under the curve", so you could use a 1:1.4 transformer, pulsing the primary with a short pulse that makes the peak voltage (kind of) correct or use a 1:1 xformer and pulse it longer (I don't know if some devices might need the full peak-to-peak or if just the average power is OK).  In any case, you want to mimic the total power delivered by a true 120V RMS sine wave in each cycle.  This is what "modified sine wave" inverters do.  They can be the most simple (and least expensive) circuits to build or buy, though they have their drawbacks.

Thanks DanB I'll check into the surplus situation for computer UPS - though I'm itching to build something - you know how it is...

ibedonc - I am aiming at something around 1200 watts with a surge capability of about 3,000 to start a quarter horse induction motor. I have been reading your diary about the inverter you're working on with great interest.

RatOmeter - I saw that site too - I know it sounds nuts but I'm looking for a way to do this without a large output transformer. Not sure if that's going to be possible or not,

River Goat, sounds pretty interesting - I have read Jerry's posts on this board about the 120 VDC setup he is using at his shop. Still leaves a couple of things that need AC though - like induction motor powered stuff I can't seem to get around, at least no easily anyway. In the end I guess it will come down to which is more do-able, some kind of inverter, or changing induction motors for another type.

Thanks RobD - I kinda gathered that bit about RMS values, guess that's why a bridge makes about 1.4 times the DC voltage out of the AC input...

Still looking and if I find anything I'll post.

Having fun!

I suppose 10 12v batteries could be wired together for both 120vdc output, and 12vdc to an inverter somehow to power both??

I am enterested in this, if I can power have my house or better from DC without an inverter eating extra power.

How can you tell if something will run from dc directly, without burning it up?
If computers, monitors, and lights run straight from DC that helps alot. About 50-75% my power use I think!

Where can I find more info for this?
.
nothing to lose

Some 120v AC breakers will function up to about 30vdc somewhat reliably; but they're not rated for it and there's no way of knowing which ones you can bet your house/life on.

Inverter:  you need 170vdc supply to run an H-bridge for 120vac output.

High-voltage / High-power inverter design ain't as simple as a lot of people seem to think, from some chip-company's optimistic app-note they come across.  I've designed power electronics (servo drivers, switching power supplies, VFD's, induction heat treaters) for 25+ years, and I -still- think it's a challenge <g>.

Making a proto work on the bench is one thing...making a unit that's robust under -field- conditions...for 10 yrs or more...is another kettle of fish entirely.

My advice:  find a cheap source of output-devices, because you're going to go through them by the dozen...and wear safety glasses.

Seriously tho...about the safety glasses...do wear them whenever you power up your proto.  TO-220's etc. -do- literally blow up from time to time...even a little to-92 going south can make you think someone fired a .22 right by your head... <g>

I did UPS and DC/AC converters design and manufacture for a living -- so here is my 2 cents:
The 120 volts if you want to produce a 115 volts Sinewave AC output needs a way to convert it to +2-- and to - 200 volts ( 400 volts DC with a center tap),
Then one design a PWM circuit using a couple of POWER MosFets to generate the sinewave, properly filtered.
Unless you have a lot of electronic experience I do not recommend such project.

Nothing to lose,
Knowing what will run on 120vdc isn't too clear cut. All CF lights with electronic ballists will work, VCRs with switching powersupplies will work if they don't use the line freq for a clock. Same thing for TVs and computer monitors, all that I have checked(roughly 100)work on 120 to 180 vdc, but several use the line freq for clock purposes and these won't work. You would need to have some who understands these circuits look at the schematic. Also the degaussing circuit has to be disconnected, then it will need to be manually degaussed. Mine needs it about every five years. With electronics, when you rectify and filter 120vac you get 150volts or so but most devices work down to 120vdc. My TV will begin to lose sync below 120v. Resistive loads(incandescent blubs,coffee makers, tosters, solder irons and others) want to see 120vrms; 120vdc is exactlly that. Brush type AC motors(power tools, vacuum cleaners, weedeaters, ect.) run fine on 120vdc, the switches are the problem; capacitors across the switch has worked for me.
There isn't much around for 120vdc refrigeration Low Keep Refrigeration did make a 120vdc unit but I think he sold his buseness. I have an LP frig, but I have plans for a HVDC unit using a linear compressor.