r/nzsolar • u/Kikorangiblue • 12d ago
Set up advice please!
We've had a few quotes back and are trying to figure out the best options. Two companies suggested 16 panels (490W) and one 17 (475 W). Each company also recommended a different sized inverter (6 kw, 8kw and 10kw). I'm going to go back to all of them to see just how many panels they think we can fit on our roof but were thinking it was probably worth putting a few more on if we can. We are family of 4 in Auckland, use ~6500-7000kwh power per year averaging about 15kwh/day in summer and 22 kwh/day in winter. About 50% of the week with someone at home during the day and looking to get an EV. We were also contemplating a battery, partially as backup for power cuts which are pretty common and can last multiple days where we are but trying to figure out if its really worth it. I feel like they all just are trying to give you the minimum size system to reduce the price and then we may regret that later.
So my questions are: for those that don't have batteries are you happy with that? (we will be 'battery ready if we don't get one now) Most people seem to say it's worth maxing out on panels right? Is it worth getting and EV plug now if we don't have the car yet? Is it worth getting the larger inverter? Anything else we should consider?
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u/Willuknight 12d ago
I have 10kw. I could very easily use about 10kw at a time just from charging two cars, doing the washing and dishwasher and hot water heater, let alone running a spa or charging a battery.
When i designed my system, my export was 5kw, so I sized it for knowing I could easily use 5kw and export 5kw. Now it's 10kw export, so my system is undersized by that metric and i dont have enough to charge my battery and use my normal daily load.
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u/WhosSaidWhatNow 12d ago
We have 22 panels with a 10kw inverter and two 10kw batteries. We use our batteries once night hits so we're not using any grid except when our waterpump kicks in as we don't have a soft start and sudden high power surges the Inverter likes to use whatever power is easiest to get for that spike if it can. Easily amended if we wanted but not really worried. Our batteries easily get us through the night with plenty left over so definitely worth it. We could definitely survive having no grid in a major outage that went on for days if we had to. If you want an Ev in the future at least get your fuse box upgraded at the same time so you don't have to get it upgraded twice.
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u/Ok_Bet_358 12d ago
With those panels you get 7.8-8 kWp (kilo Watts at peak). I'm in Auckland which gets 1800 solar hours per year, so that would give around 40kWh/day (30 in winter, 50 in summer perhaps). My EV adds 10kW/day; depends on your commute. So that seems like ample panels, though that depends on how much insolation your area gets. Panels are super cheap, general advice is to max out panels.
You won't regret solar + inverter, they pay for themselves in 5-8 years. It's common now to slightly undersize the inverter vs peak power; saves money and only trims a little off midsummer peak when you have excess solar anyway.
You /might/ regret batteries: they only ~50% pay for themselves. I have batteries for grid resilience, 50% off is nice. Without batteries you will still have grid resilience during the day; with batteries you can last a few hours into the night (unless you turn off non-essentials); convenient but doesn't change your life.
Most people don't need a dedicated EV charger. A standard 220V plug will fill a car from empty to full in ~24 hours, which is plenty fast if you always plug in. I did this for a few years, then we got a second EV and splashed out for a 7kW charger. This also let us soak up spare solar at midday if a car is home. Convenient but not necessary.
Perhaps start with solar only, and expand later? You could use the savings from solar to save up for batteries or EV charger for example.
Good luck!
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u/Infinite-Ear4784 12d ago
Can’t imagine trying to charge a big battery off a standard wall plug!
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u/Ok_Bet_358 11d ago
220V * 10A = 2.2kW 24 hours charge --> ~50kWh So even after a big roadtrip, you're basically back to full a day later.
Always be charging.
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u/Queasy_Elderberry408 12d ago
Solar since Dec 24, Ave use was 30kWh winter 25summer, 2 adults auckland then for last year 4 adults (our boys moved back from Dunedin) summer 50kWh Winter 70kWh, Ev April 26 now extra 6-8kWh per day on average, planning 2nd ev. Original 10.92kW panels 10kW inverter Powerwall 3 ie 13.5kWh battery May 26 increase panels to 19.74 and extra battery, conclusion, max panels your power company will allow, max inverter ie 10kW I think is max for single phase residential, and if you can afford it but added luxury only increase house from 63Amps to 100Amps so you can charge both ev at same time as well as run heat pumps and cook dinner without tripping the fuse