A Grid Tie inverter (which is the most common type) needs to synchronise to the grid, the result being no grid, no output
Some "hybrid" inverters have the ability to provide backup power but most dont
Ive been on the solar/off grid journey for the last 5 or so years.
I started with 5kw of grid tied solar that came with the house.
We monitor this using software, in fact every circuit is monitored for power use.
The first thing I did was add a 21kw 3 phase diesel genset. Enough to power the whole property
I then added an ATS to switch on the genset when the grid was out and changeover to the genset
This is a
4PRO ATS-63A-4P-RSC
I logged the solar for the first 2 years before upgrading it
My best production was 35Kwh/Day and the worst (during a 3 days of a cyclone) was 8.5kwh/Day
On the consumption side we average 22kw/h day (8Kwh at night). So no issue with the genset.
My next step was adding more solar and battery
I went with a 48v Lifepo4 battery bank (400ah cells) giving me 22kw/h of storage or enough for one day
Using the data of my worst day I added 2 more 5kw solar systems. This guarantees me 24Kwh of energy per day or more than enough to get full charge every day.
To make all this work I added a
selectronic inverter charger. This sits between the grid and the inverters & loads. I also connects the battery bank and genset.
On a normal day I have full charge by 10am and am exporting energy to the grid from 9am. On average I export 90kwh a day.
3 years down the track with battery no additional costs we are half way to covering the investment with saving from no power bills. As it breaks down 6 years to pay back to the investment in savings. another 3 to cover cost of replacing battery and panels at 15 years. the last 6 years are free. That all assumes grid power prices does not go up (not likley) and battery/solar does not come down in price (no likley either)
Oh yeah have never needed the genset to top up the battery. I have started it for 3 phase power during a storm however. With the power out the grid tied solar still charges the battery and the the inverter charger supplies power from solar and battery. If the battery gets to 50% charge the genset will start and top up the battery with the solar still running.
In terms of costs it all was the about the same as a new BX23s