Hello folks,

We are in a 2-year-old house build so the coloursteel roof has plenty of life left in it. Our house design is a H shape, so we have a 23M long straight high pitch roof in one part of the house and 15M long straight in another part of the house with both sides of roof facing North with no shade at all which is a bonus. We are with Genesis on a recently signed 2 year contract for electricity + natural gas. Only hot water is on natural gas. Cooktop is up to 11kW induction, balanced pressure ventilation system with summer bypass mode and heat exchanger is integrated with ducting for aircon as well. We have a ducted aircon that's 14kW cool and 16kW heat with no zone control. 

Our average daily electricity usage is between 50kW to 60kW, and average monthly is between 1100kW to 1400kW. I have been checking our daily and hourly usage in the Genesis app/website and most of our usage is at nighttime between 10PM to 8AM that is 95% ducted aircon averaging between 5kW to 7kW every hour. Ventilation system uses 0.50kW every hour. The monthly power bill only is between $320 to $350. We do not have an EV but the next car will likely be one which is likely atleast 5 years away. Both me and wife work from home 3 days a week.

The wish is to bring the power bill down from $320 to $50 per month or lower with solar and selling excess back to the grid. Genesis does offer 12c/kW for export back to grid. Lines company is Waipa networks. 

I have contacted 4 installers in our area incl Harrison's to come and provide a scope and quote. 3 of the installers will be visiting next week with Harrison's is so busy that earliest appointment they had was 12th of October. We have applied for Westpac's 5-year interest free $40k loan for Solar and waiting to hear back from the bank as well which should not be an issue. 

From the research I have done, I have come up with below possible solutions. Can you please provide your knowledge if these solutions are worthwhile or recommend an alternative. I am thinking that because we use lot more power at night, we need a setup with battery and that a single 6kW inverter with 9kW of panels + 15kWh battery will be a good starting point? I am hoping that both solution 1 and solution 2 will be $15k or under. I am specifying BYD batteries because they are Phosphate Iron with no Cobalt so zero chance of fire/explosion and they provide slightly more kWH than Tesla Powerwall 2 for same price. 

Solution 1 - SMA 1 x 6kW Sunny Boy inverter, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). I could then in 2 years' time or break my Genesis contract now (will cost me $150 or $200) to move to a higher daytime rate plan but much cheaper nighttime rate plan to offset ducted aircon costs during night? Currently we pay flat 24cents/kW incl GST - 15% discount. 

Solution 2 - Fronius 1 x Gen 24 Plus inverter, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). The benefit of the new Gen 24 Plus inverter is that they have a much bigger heatsink with fan and has up to 3kW PV point connection in case of a blackout, but I believe this feature will only work with battery storage and that during a blackour in daytime, solar panels along cannot provide power to this PV connection? 

Solution 3 - SMA 1 x 6kW Sunny Boy inverter, SMA 1 x 8kW Sunny Boy Island inverter, 1 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). While this battery storage will not take care of all energy needs for nighttime duties, it should reduce the on-grid usage by 70%? I am hoping this solution will cost under $35k. The big pull for this solution is that in the event of not only a blackout but an extended power outage from grid, the Island inverter can then power up the entire home using panels in daytime while also charge up the battery storage if I am correct?

Solution 4 - Fronius 1 x 6kW Primo inverter, Victron 1 x Multiplus-II 48/5000/70-50 230V inverter, 1 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). The Victron Multiplus II is $2k cheaper than SMA Sunny Boy Island inverter. I am hoping this solution will cost under $35k. The big pull for this solution is that in the event of not only a blackout but an extended power outage from grid, the Island inverter can then power up the entire home using panels in daytime while also charge up the battery storage if I am correct?

Solution 5 - SMA 1 x 6kW Sunny Boy inverter, SMA 1 x 8kW Sunny Boy Island inverter, 2 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). I am guessing this will cost just under $50k. I am happy to spend the extra $10k from pocket and this 30kWH will likely keep me off grid for most days of the year if I am not wrong? 

Solution 6 - Fronius 1 x 6kW Primo inverter, Victron 1 x Multiplus-II 48/5000/70-50 230V inverter, 2 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). 

Solution 7 - SMA 2 x 5kW Sunny Boy inverter, 30 x 420W (12.6kW) REC Alpha Pure panels (for all black look) or 30 x 420W (12.6kW) Q-Cell Q-Peak Duo G10 (for all black look). I double up on the inverter and add more panels to maximize sell back to grid and when we have more $ down the track, add the islander inverter/charger and battery later. I am hoping this solution will cost under $30k.

Solution 8 - Fronius 2 x 5kW Primo inverter, 30 x 420W (12.6kW) REC Alpha Pure panels (for all black look) or 30 x 420W (12.6kW) Q-Cell Q-Peak Duo G10 (for all black look). If I am going to add the battery later for my solution, then I do not want to go with Fronius Gen 24 Plus inverter as it would mean then I would need to buy BYD HVS or HVM battery (400V) which costs more than their LVL Premium (48V). I am hoping this solution will cost under $30k.

Below is current month's ongoing electricity usage. 

Below is a day's hourly usage breakdown with aircon running through the night.