Tesla Powerwall vs generators - South African pricing compared

lsmt said:
3 x 3.6 kw Lifo batteries = R60000 plus 10kw hybrid invertor = R33000. Sundries R20000. Total R113000. Tesla want's to steal what's left in our country. To expensive.
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Tesla Powerwall 2 has a capacity of 13.5kWh will 100% DoD with a 10 year guarantee.
3 x 3.6 kw Lifo batteries = 10.8kWh with typically 80% DoD giving 8.6kWh usable.
To reach the same capacity as Tesla Powerall 2 you will need 4 or 5 of your 3.6kWh.
That will make your between R133,000 to R153,000.
Tesla may be more expensive, but not unrealistically so based on the capacity.
 
dingaanone said:
My hobby over the past 5 years has been buying, installing and testing different solar equipment at my own residence. I also purchased a 6.5 kW generator and believe me my message has nothing to do with sales, when I started using solar equipment my bill was around R7000 a month and after increases over the last couple of years I am running a bill of between R3000 and R4000 per month currently. Pool pump 3 AC units 4 Fridges Ice Machine 2 geysers (Also linked to solar water heating system)
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In those 5 years, how often have you been unable to buy fuel for your generator?
 
Speedster said:
In those 5 years, how often have you been unable to buy fuel for your generator?
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Was going to ask the same question as in SA the petrol stations have all switched over to backup power supplies themselves.
Even ones on the N3 down to Durban have got them.
 
The real operating cost in any home solar system is the replacement cost of the batteries.

So how long do the batteries last in a Powerwall and what does it cost to replace them?

For eg, normal high quality lead acid batteries might have about 2000 cycles at 50% DOD, which in a solar application means they cycle every day, so that means the batteries will last about 2000 days if cycled to 50% each day. So that is a bit more than five years.

That is your actual cost of electricity in a home solar system (the cost of the panels etc is much less in comparison because they should have a life of about 20-30 years). If you take the cost of your battery bank and then divide the total stored energy over the life of that battery bank you should get an operating cost that you can compare to other energy sources.
 
alanB said:
The real operating cost in any home solar system is the replacement cost of the batteries.

So how long do the batteries last in a Powerwall and what does it cost to replace them?

For eg, normal high quality lead acid batteries might have about 2000 cycles at 50% DOD, which in a solar application means they cycle every day, so that means the batteries will last about 2000 days if cycled to 50% each day. So that is a bit more than five years.

That is your actual cost of electricity in a home solar system (the cost of the panels etc is much less in comparison because they should have a life of about 20-30 years). If you take the cost of your battery bank and then divide the total stored energy over the life of that battery bank you should get an operating cost that you can compare to other energy sources.
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You really shouldn't even be considering lead acid in solar
 
alanB said:
Well I would say it all comes down to operating costs, I would go with the option that yields the lowest operating cost. I'm not really familiar with the numbers off the top of my head anymore.

I wrote an article about it a while back https://offgriddiy.co.za/how-to-compare-solar-batteries/
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Lithium based batteries are far superior in every way for solar applications. Lead-acid is only feasible in a pure backup scenario, if there is any cycling involved lithium will be a better option. Most lithium batteries have in excess of 10 year life expectancy.
 
Speedster said:
Lithium based batteries are far superior in every way for solar applications. Lead-acid is only feasible in a pure backup scenario, if there is any cycling involved lithium will be a better option. Most lithium batteries have in excess of 10 year life expectancy.
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Yes I know, but what are the numbers?

I'm not familiar with them anymore, so your statement above is a bit like saying a Ferrari is a better car than a Toyota - which may be true, depending on how you define "better".

I would say, again, for most homeowners it comes down to operating costs. So what are those costs?
 
alanB said:
The real operating cost in any home solar system is the replacement cost of the batteries.

So how long do the batteries last in a Powerwall and what does it cost to replace them?

For eg, normal high quality lead acid batteries might have about 2000 cycles at 50% DOD, which in a solar application means they cycle every day, so that means the batteries will last about 2000 days if cycled to 50% each day. So that is a bit more than five years.

That is your actual cost of electricity in a home solar system (the cost of the panels etc is much less in comparison because they should have a life of about 20-30 years). If you take the cost of your battery bank and then divide the total stored energy over the life of that battery bank you should get an operating cost that you can compare to other energy sources.
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The definition of a cycle is one discharge / charge cycle to 100% DoD.
The above definition applies to Lixxx batteries and as far as I know, also to XLA batteries.
So an operating regime of 50% DoD implies 4000 "cycles" as defined by your operating regime.
lixxxx batteries are able to be cycled as above, but there are many factors that affect the cycling of xLA batteries which generally means not many ever get the lifetime cycles quoted in specs.
 
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Geoff.D said:
The definition of a cycle is one discharge / discharge cycle to 100% DoD.
The above definition applies to Lixxx batteries and as far as I know, also to XLA batteries.
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Most battery manufacturers will publish a curve showing the expected life in number of cycles at different depths of discharge. So one can use that.
 
Pylontech does just that. 10k cycles with DoD @80%, giving 60% useful life. Thats more than the 10 year guarantee they offer on the batteries, once you’ve registered your installation with them. Still more expensive than lead acid, initially but then these batteries can be cycled each day storing excess PV, making them more affordable over a 10 year period vs LA. It was a different story even 5 years ago.
 
gbyleveldt said:
Pylontech does just that. 10k cycles with DoD @80%, giving 60% useful life. Thats more than the 10 year guarantee they offer on the batteries, once you’ve registered your installation with them. Still more expensive than lead acid, initially but then these batteries can be cycled each day storing excess PV, making them more affordable over a 10 year period vs LA. It was a different story even 5 years ago.
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Do you have prices, to plug into these equations? https://offgriddiy.co.za/how-to-compare-solar-batteries/

If I get the chance, maybe on the weekend I will build a little web page calculator for that, meant to do that some time ago, in any case. That way people can compare different batteries themselves.
 
gbyleveldt said:
Pylontech does just that. 10k cycles with DoD @80%, giving 60% useful life. Thats more than the 10 year guarantee they offer on the batteries, once you’ve registered your installation with them. Still more expensive than lead acid, initially but then these batteries can be cycled each day storing excess PV, making them more affordable over a 10 year period vs LA. It was a different story even 5 years ago.
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That is correct but it is still quite tricky to ensure a proper apples for apples comparison is made between batteries.
 
alanB said:
Do you have prices, to plug into these equations? https://offgriddiy.co.za/how-to-compare-solar-batteries/

If I get the chance, maybe on the weekend I will build a little web page calculator for that, meant to do that some time ago, in any case. That way people can compare different batteries themselves.
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4 x 200Ah LA = R20000
4 x 12V x 200A = 9.6kWh
50% DOD = 4.8kWh
2000 cycles = R10/cycle
After 2000 cycles = replace

2 x 3.5kWh LFP = R40000
80% DOD = 5.6kWh
6000 cycles = R6.66/cycle.
After 6000 cycles = 60% capacity.
 
lsmt said:
3 x 3.6 kw Lifo batteries = R60000 plus 10kw hybrid invertor = R33000. Sundries R20000. Total R113000. Tesla want's to steal what's left in our country. To expensive.
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It would be interesting to see how much the Powerwall will retail for here if it's exempt of all taxes applicable to import and distribute the unit. I have long been of the opinion that PV (and related items) + rainwater harvesting tanks should be zero rated items.
 
alanB said:
Do you have prices, to plug into these equations? https://offgriddiy.co.za/how-to-compare-solar-batteries/

If I get the chance, maybe on the weekend I will build a little web page calculator for that, meant to do that some time ago, in any case. That way people can compare different batteries themselves.
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Well, as a thumbsuck, a 3.5kW Pylontech battery is around R23k retail. It's about the best R/kW value in their product line. FWIW, Pylontechs can only be charged/discharged at half C. Thus 1.7kWh on a 3.5kWh battery. And the BMS would trip out at a DoD of 89%; I usually only let the battery get to a DoD of 70% in order to give me a little capacity available for load shedding in the mornings, before the PV panels can get into gear. So maybe something to consider in your calculations. As @Geoff.D stated above, it's a little tricky to do an apples to apples comparison. Still, it's better than LA DoD cutoff of 50% and 2000 cycles (when the moons align).
 
wingnut771 said:
4 x 200Ah LA = R20000
4 x 12V x 200A = 9.6kWh
50% DOD = 4.8kWh
2000 cycles = R10/cycle
After 2000 cycles = replace

2 x 3.5kWh LFP = R40000
80% DOD = 5.6kWh
6000 cycles = R6.66/cycle.
After 6000 cycles = 60% capacity.
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And there you just made it real simple :)
 
wingnut771 said:
4 x 200Ah LA = R20000
4 x 12V x 200A = 9.6kWh
50% DOD = 4.8kWh
2000 cycles = R10/cycle
After 2000 cycles = replace

2 x 3.5kWh LFP = R40000
80% DOD = 5.6kWh
6000 cycles = R6.66/cycle.
After 6000 cycles = 60% capacity.
Click to expand...

Nice!

Slight correction, not meaning to be a smart Alec:

First eg: R20,000 / (9.6 x 0.5 x 2000) = R 2.08/ kWh Cycle

2nd eg: R40,000 / (7 x 0.8 x 6000) = R 1.19 / kWh Cycle

Not sure about the 60% capacity though, my understanding of these graphs is that represents the full extent of the battery life?
 
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