And the lights stay on...
Part of what makes our house unique is our backup power system. Power outages around here are commonplace. You can count on the power going out whenever there is a thunder storm. Ice storms in the winter have the same effect, and the outages can last for days, even a week or more. What is odd, though, is that sometimes, the power will go out in the middle of a sunny day!
Instead of a gasoline or propane powered generator, which is what most homes that have backup power use around here, we have batteries and an inverter. The inverter is a Trace (now Xantrex) 4000 watt continuous sine wave model. It converts the 48 volt battery power to 120v AcC. It also keeps the batteries charged and in top shape. When the grid is up, the inverter gets the power it needs to keep the batteries charged from the grid. When the grid fails, the solar panels feed the batteries, through the inverter.
These are MK batteries, model 8G31DT (Battery Specifications Pdf 8G31DT). They are sealed, gel cell batteries, so there is no topping off of water, they are maintenance free. There are three banks, each with for, 12-volt batteries, wired in series to give 48 volts per bank. They are not expensive "Solar Batteries" because in this application, they would be overkill.
When the grid goes out, there is a little hiccup, while the inverter kicks in. It does not provide power to all of the circuits in the house, rather, the so-called critical Loads, such as the refrigerator, well pump, lights, the furnace blower, internet router, and of course, the TV. Not all of the lights are backed up, just some in each living area.
Since we moved in, we have not had to test the full capacity of the batteries, since the longest outage we have experienced was about 4-5 hours.