Solar isn't practical to use during a power failure without a battery bank, which gets very expensive very quickly, and requires fairly frequent battery replacement. The more economical solution is almost certainly to leave the solar panels grid-tied, and install a generator for power failures. The inverters *may* work while the generator is running and save fuel bills; hard to say without more information on the model of generator and details on the interver.
I know my little UPS unit hates my portable generator with a passion, so there's something dirty going on that might not play nicely with the inverter(s).
