Solar panels needed ?

marine1

marine1

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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
 
marine1 said:
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
Click to expand...
OK will give you my setup to use as an example.

I have 10kWh battery storage. They are set to only go down to 40% SOC. So I use 6kWh out of the batteries every night. This is recharged at 40A and is usually back to 100% SOC at around 11:20-11:30 am. I could set a more aggressive charge at say 60A and I believe they will be back to 100% SOC quicker. Afaik.

I only have 6.7kW of panels. 16 x 420w panels.
I am sure there are other members with similar setups of 20-30kWh of battery storage that can give better real-world examples.
 
Have you done an audit of your place to determine when you use how much electricity and what your peaks are?
With some kind of efergy meter or the like.

If you have this data you can make a much more informed decision on what system to get. With 16kW inverter and 30kWh batteries you are pretty much sorted for most situations.

I would however investigate the option of using 2 x 8kW inverters for redundancy. 2 or 3 x 10kWh batteries should offer enough redundancy should something go wrong.

What batteries are you looking at getting? Are they 1C rated?
 
dont know how accurate these things are but heres something google spat out.

nrgeneration.co.za

A Guide to Size a Solar System - Next Renewable Generation (NrG)

As loadshedding is slowly becoming a normality in South Africa, many are looking towards solar systems as a way to keep the lights on during these dark times. However, common questions such as how big of a solar system is needed or how many solar panels are required, often form the basis of this...
nrgeneration.co.za nrgeneration.co.za

seems like around 5hrs per day of peak sun time is the average in south africa.

10kw of panels will should charge your 30kwh battery in about 3 hours. but then there are consecutive cloudy days too...
 
you would need to know first off how much electricity you use, "like a spike" geyser going, oven on, tv, pc etc... lets say that spikes to 11kw and comes down, so the max you would ever use would be 11kw. Any invertor bigger than that is fine, too much is a waste and too little it would either trip or go to Eskom for the extra load.

the panels would be paired to the max voltage and strings of that invertor

and the batteries, well you can have a million of them, that just determines how long you want to use the power stored in them with zero help from the panels, eg. night time. during the day the panels are prioritised then batteries then Eskom.

PS: Don't look at your monthly Eskom usage, look at your max demand in one go. This will help you get completely off grid one day. These all help reduce your max load at any time.

1) Solar geyser
2) All LED lights
3) Gas hob / electric oven
4) Invertor aircons

Remember you can only get around 14kw off the street unless you have 3 phase or have specifically asked for a bigger demand from Eskom when you built the house.
 
marine1 said:
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
Click to expand...
you can follow my story here https://mybroadband.co.za/forum/threads/snypers-solar-farm.1161046/

I would recommend you up you batteries you honestly want a min 20kw

sorry I see you aiming at 20-30kw already.

I think you on the right track over specing my system was the best thing I could have done wish I popped on about 4 more panels but zero complaints otherwise
 
Clean Green said:
Hair-dryers and those fancy machines are power hungry, this will impact the amount of panels required, which is why I highlighted it.
Click to expand...
His inverter covers that. As long as he has battery juice he will be fine in loadshedding.
 
Pegasus said:
His inverter covers that. As long as he has battery juice he will be fine in loadshedding.
Click to expand...
I was more thinking in terms of battery recharging. I run an inverter aircon sometimes and during winter (because I only have 8 panels * 460w) I can't always get my batteries fully charged.

If the goal is loadshedding, then happy days. If it's to get off the grid, randomly pulling, 2000w 30 minutes at a time, it might affect his use case.
 
Number of panels will depend on the angle of your roof, amount of space, amount of cloud cover and time of year.

If its North facing then you'll probably be fine starting with 12 to 16 which most people seem to have. You can always add another string of 6 to 8 later.

So buy some this year, claim for tax and then next year buy after Feb and claim tax.
 
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Pegasus said:
Number of panels will depend on the angle of your roof, amount of space, amount of cloud cover and time of year.

If its North facing then you'll probably be fine starting with 12 to 16 which most people seem to have. You can always add another string of 6 to 8 later.

So buy some this year, claim for tax and then next year buy after Feb and claim tax.
Click to expand...
As far as I am aware, the tax rebate of 25%/R15k was only available for the 2024 tax year.
 
Philip-d said:
As far as I am aware, the tax rebate of 25%/R15k was only available for the 2024 tax year.
Click to expand...

It looks like you are right.:crying:

FAQ: What is the SARS solar tax benefit? | South African Revenue Service

This incentive is available for one year between 1 March 2023 and 29 February 2024. Individuals who install rooftop solar panel(s) can claim a rebate of 25% of the cost of the panels, up to a maximum of R15 000 per taxpayer. Taxpayers can use the solar tax rebate to reduce tax liability in the […]
www.sars.gov.za www.sars.gov.za

I wonder why they don’t extend it then?
 
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