Solar panels needed ?

[Tantric Smurf]

How would one work out how mnay panels is needed in a house?
I am working on the following:
Monthly City Power cost about 4-5k
Needing 2 or 3 10kw batteries - so they need to be charged during the day and still have enough power to run the house durig the day.
Working on a 16kw inverter, yes its big but I want to have something bigger if needed in future.
So based on this, how would one work out what would be needed? Can someone please explain the formula?
I am assuming i would need upwards of 25 panels?

Thanks

Depends on your time of use and peak power demand.

16KW inverter is rather a beefy oversizing and not always future proofing. There is constant wear on it from the moment it is switched on. It is important to go bigger than what you think to reduce the workload on the inverter. I went with an 8KW unit after originally only thinking I needed 5KW. Glad I did.

I have an 8KW Deye with 4,5KW panels (number of panels is irrelevant, it is the combined power production that counts). Battery is 10,5kw capacity.

At my first solar-versary now and produced in my first year 6MWh while consuming 11,6MWh power (so only bought 5,6MWh power). Will improve this coming year as I've learnt to shift demand better and reduce wasted production.


What I have learn't is to lower my peak demand to make use of sun and battery better. Your battery output needs to also handle this. I made the mistake of confusing battery capacity with output and had to double up my battery in the end. Could only output 2,5KW per battery.


If you have the luxury of dropping R500K on a system, go for it, else start small.

There are lot's of miscellaneous and installation costs for these bigger systems. Filling up a cart with just panels, battery and inverter is no indication of final cost. For example, for me to add a third battery will cost me R5K more as I now need to have busbars installed, new cables, new fuses, KFC meals, etc. You need more DC fuses and breakers for more strings, more conduit installed for your wires, more this, more that.

 

[Tantric Smurf]

Agreed it is about 2000 watts to be used intermittently throughout the day, not all the time but will be used throughout the day

You need less than what you think. Single stylist, 2400Watt hairdryer, 800W hood dryers, 12000BTU aircon, coffee machine, point of use electric geyser and a household.

This usage is from a public holiday my wife worked, kids on PCs, me making food in the kitchen, home geyser on.

System only failed me during load shedding when we had the single battery. We did find that the second battery smoothed out the power better during load shedding. A few installers confirmed that this will happen for demands like ours.


You can see left/right side is house. Middle section is hair salon and my wife had a very, very busy day.

 

[calypso]

Buy a device like an efergy hub to monitor your power consumption over a period of time. Can guarantee that you dont need a 16kw inverter (that's 70a for 230v AC), if you do, your load management is **** or you have a few electric cars.
In terms of how many panels, how much north-facing roof do you have? That's how many panels you need.

 

[SauRoNZA]

As many as you can fit on the roof, it's the only part of the entire setup that has a return and keeps on giving back for many years to come.

So I would rather look at how much can you actually fit in Northern, Eastern and Western facing direction from there.

I was spending R2500-R3000 a month and settled on 6.3kW in panels and I reckon it's adequate but I should have gone for more.

Also my 8kW inverter with only 2 MPPT's was a mistake and make a upgrading hard now. I should have done 2x5kW unit instead.

If I had to redo my setup right now I would get a 12kW inverter for the 3 MPPT'S and install 10kW-ish in panels. 2 kW West, 2 kW East and then 6 kW-ish North.

***

Also you just need to sense check the 16KW inverter and make sure it covers everything you want. For instance it's unlikely to support a 16kW solar input and also remember when load shedding you are battery limited so they would need to be 16kW ready to cover that.

I reckon you would be just fine on a 12kW, especially when not load shedding as the grid can cover any extremes.

My entire house runs on an 8kW with an electric geyser and three non-inverter aircons with a normal stove and oven.