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Standard questions need answering first.
What input voltage?
What output voltage?
What wave form?
Did you look on line for one already built that meets your answers to the above requirements?
make one from a UPS...... or at least from the transformer and transistors from a 1000W (better if it's 1200W) UPS. it takes a bit of circuit "trickery" to convert one directly, and more often than not, they're actually running 24Vdc from the batteries, which means looking at several until you find one that uses 12V.
problem is for 1kw, you need a lot of primary current, in excess of 100A, so for instance, for a converter with 80% efficiency, and a step up ratio of 10, you will need ( Iout*10)/0.8= 125A input current at 12Vdc. everybody says to themselves "1kw at 120V? that's only 10A.......", but the same power is 100A at 12V, and it takes energy to convert, so that translates into more power to run the converter, which takes more current. you need transistors (or banks of transistors) that can handle 150A (safety factor, and a 20% safety factor is marginal). actually the step-up ratio is a bit higher voltage wise, since it takes a total swing of 340VP-P to get 120Vrms, but your RMS voltage and current for 1KW are what counts here.
125A is a lot of current, and it takes a large battery to source that, and "heavy iron" to get it from the inverter circuit to 120V outlets, and there's a lot of heat sink area required for the transistors.
so between the batteries and transformer and heat sinks, there's quite a bit of weight. if it's a school project, i recommend you get the parts from a UPS, and create your own 60hz oscillator and amplifier. if it's just a home project and you want one to run something in your barn or whatever, get one that you can find the schematic for, and find out how to fool the oscillator logic into working without having it connected first to a power line. the good thing about a UPS, is that they usually have their own AC circuit breaker and outlets...