Adding battery backup

papab

I have a grid tied system and would like to add battery backup.   I live in sunny Colorado.  All electric home.    

Currently: 4.4 kw on roof, and 5 kw Sunnyboy  GTI.

On good days I get 30 kwh from the panels.   Average during dec-mar is 19 kwh.

Typical winter consumption is 30 kwh.   I can cut way back on that if needed with lower house temperatures, and less cooking (or use a propane camp stove).   The house hasn't dipped below 50F when empty..

 

I could get by with about 10 kwh just to keep the fridge and freezer going for 1.8 days, but  I'm thinking more would be nice, 30 kwh since that matches the peak production.   

With 30 kwh I can go a about 4 days with no sun in frugal mode.    With typical weather (& sun) I can be comfortable for many days.   

Max power is driven by the sewage pump which needs 6500 W for startup.

Does this seem reasonable?

Would the grid tie inverter become surplus and be replaced by a hybrid inverter or is there some way to leverage that?   

Canadian Solar and Fortress are the hardware providers that I've looked at so far.   Any other companies to consider?