Off-grid System for big house and large family in NSW

I need to install an off-grid system in NSW (south of Sydney) that will power a very large house. Grid connection is not available so I need to relay 100% on the solar system with a back up generator. I’ve received a quote from a company that has been very helpful in working out what I need but I want to make sure the quote seems reasonable before I go ahead.

We’ve worked out that I will use approx 50kWh per day. Its important that I get a system I can add to down the track if needed. Ive been given a few options:

Option 1. $110,000
AC Coupled - 48v, 21.08kwp, 27kVa Victron Controller, 69kwhBYD lithium storage

  • 5x BYD B-Box 13.8 LV PRO (IP20) Lithium -ion (LFP) battery unit (69kWh: 92% usable)
  • 68x Trina Solar TSM-310 HoneyM Plus monocrystalline (BF) solar panels (21.08 kWp)
  • 2x Fronius Primo-8.2-1 Solar inverter

Option 2. $140,000
Optimised AC Coupled - 120v, 21.08kwp, 20kVa controller, 66kwh Powerplus LFP lithium storage

  • 20x PowerPlus: High Performance 120V rack mounted L-ion (LFP) batteries inc. 800/600/1950 IP21 20 module cabinet (66kWh: 100% usable)
  • 68x Trina Solar TSM-310 HoneyM Plus monocrystalline (BF) solar panels (21.08 kWp)
  • 2x Fronius Primo-8.2-1 Solar inverter

Do these prices seem reasonable? Which system would be best? Is there any way we can keep costs down without sacrificing quality and that will still provide us with enough power?

Unfortunately these quotes are more than double what we originally allowed for in our new home budget and we struggling to find the extra. With Option 2 (above) we can do it in 2 stages which may help. We will initially be living in a shed while the house is being built so wont need as much power to start with. Stage 1 includes everything except for 10 of the batteries and is $96,000. Stage 2 adds the other 10 batteries and is $48,000. After we move into the house, the solar system will stay on the shed but power both the house and shed.

What are your thoughts?

First of all I must say 50kWh per day is huge? I’m assuming this a home and business operation? The size and cost of an off-grid system is directly related to the amount of daily energy consumption.
With this amount of consumption you will also require a back-up generator, have you discussed this as well?

Those prices are very reasonable for the size of the system. The batteries alone are worth around $50,000 plus you have the huge 20kVA + inverters and large solar arrays. There is a lot of specialist labor which goes into installing and configuring off-grid power systems so it’s not cheap.


Thanks for the reply, Jason.

Yes, it is a big system as we have a big house and run a business from home in a large shed. We’re currently using up to 70kWh per day but the new house is being designed to be much more energy efficient so we think we can get that down to 50kWh.

When we first set out a budget we were advised a large off-grid system would cost around $50k but at that stage nobody (including us), had worked out just how big it would need to be. That’ll teach me for not checking it out earlier.

We’ve only been quoted by one company and they have been very helpful so I was just looking for an opinion on the fairness of the price before we go ahead. Sounds like its reasonable so we’ll get moving on it.

I would advise to have more panels, Generation power is essential, solar panels are not expensive. I would say 30kW of panels or more.
You can have less batteries, battery wold be easy to add later if needed.
Panels as well will save you on generator fuel.

And one more, I believe you still can be with in $50k may be 60max