I don't know anyone here with solar so wanted some advice. We're building here in New Zealand and have an acre of sloping land forwards of the house so have quoted up 7kw of ground mount 380w panels with 15.6kwH (usable hours) of lifepo4 batteries, 2x 5kw hybrid inverters with grid tie as backup. I'll build the ground mount base myself and run the trench to save cost. It would take 10 to 11 years of power bills to pay itself off and an extra 2 to 3 years of mortgage interest if we borrowed the money for it the whole time (realistically probably pay it off gradually and come to half that amount of interest) presuming nothing breaks after the 5 year warranty. It'll make 24kwh of power on shortest day of the year when sunny, can program batteries to only charge from solar and not grid backup and we'll produce enough excess power in summer to pay for any grid use over winter I'd think.

Does that pay off period sound reasonable? I could go just grid tie (no batteries) for slightly under half the cost and it would pay itself off in around 6 years bases off a high buy back rate one power company is offering but they may change that in future.

Edit: we're off grid for water and septic too so is a nice tie in with that