Battle of the Grocery delivery apps – Checkers Sixty60 vs PnP Bottles – who won?

My PnP Bottles Review
Pick and Pay Bottles Grocery delivery – a review | Going Solar
My Checkers Sixty60 Review
Checkers Sixty60 Delivery – a review | Going Solar

Both orders I made had teething issues.
Process for managing issues on both apps / services is a bit lacking, as is driver training.
Overall the Checkers app is substantially better, although limited in the size of orders you can make (one motorbike load). The Checkers App substitution mechanism is highly non-optimal though, as it needs to be done on a item by item basis. I also couldn’t see any “specials” via the App. i.e Store Card specials. If you wanted to get those, you’d need to go to the shops in person. Not sure why that can’t be integrated into the App – they have your store card details already in there, tie it in! PnP had some specials in app, although similarly to Checkers, none of the PnP store card specials are listed.

Both options really need you to check the order you’ve received VERY carefully – (ideally before the driver tries to leave). In my view, both need to provide a printout of the order that you can sign off on. Preferably making the driver make you sign., which other delivery companies do. Neither do that yet.

Was unhappy at the time with the checkers substitution that I couldn’t return. I have noted that you can select “don’t substitute” items, but again, its seriously inadequate when you need to select that individually, per item, per order.   I should probably deduct a point from my scoring for that UIX atrocity.

Packaging for Checkers was a lot more re-usable, and more environmentally friendly. The brown paper bags are great. The PnP plastic ones are horrid, and not re-usable – there definitely needs to be some attempt made to make that packaging better – we only have one planet PnP…

Would I use either again?

While the overall ease of use of the Checkers Sixty60 process was a lot better, the limited ordering for the relatively high cost of delivery makes it less worthwhile for me, especially when its not 60 minute delivery. I checked again today in their app, and I got offered delivery options for tomorrow only – nothing for today (and that was when I checked at 11am this morning).

The PnP Bottles app – while buggy, at least lets you order more items, and that in itself makes it more worthwhile, as the value proposition is better. Not sure that its fair on the delivery driver though – especially if they only deliver by Motorbike.
I’ve seen the Tuk-tuk’s roaming around before where I live – why aren’t those being used? That edges it slightly over the Checkers ordering for me, even with the wobbly edges.

As I know people that know people, ahem 🙂 I’ve forwarded both reviews, and my summary to relevant people at both companies, and will update if I get any feedback.

Pick n Pay Bottles Feedback
Pick n Pay are the first to get back to me – relatively quickly too!
Their response arrived a day after my request for info to them.

Pick n Pay’s reply in full below (any personal information has been redacted)

·  Bottles was recently acquired by Pick n Pay. See article here for reference.

·  The app name is currently Bottles by Pick n Pay, as Bottles is an existing delivery app which was recently acquired by Pick n Pay. Bottles was launched in 2016 as South Africa’s first on-demand alcohol delivery app, and partnered with Pick n Pay Liquor in 2018. Following the prohibition on the sale of alcohol in March, Bottles in partnership with Pick n Pay re-purposed its app within four days, emerging with a new offering to deliver on-demand ‘grocery essentials’ to customers. 

·  Bottles Privacy Policy is available on the app and website: see here: This is available during registration, from the app main menu (under Support and on our website) 

  • We are currently working on integrating Bottles App & Pick n Pay Online into one business and team, and the mobile app’s Privacy Policy and Pick n Pay’s Privacy Statement will be updated accordingly
  • In terms of information requested on registration:
  • Customer’s name is used to address and identify the customer
  • Mobile number is used to ensure someone is available for the delivery and to contact for any issues regarding the delivery
  • Email address is used for sending of invoices and order details, as well as for marketing related deals and offers
  • Date of Birth is used to ensure we only allow the sale of alcohol to people over the legal age
  • A few other comments:
  • Driver: 
    We do allow driver tipping in the app as part of the order process. You may also decide to tip the driver in cash if you prefer. 
  • The driver is paid in full for all deliveries, if he needs to make multiple trips, he will be paid for multiple deliveries and Bottles takes on this cost on behalf of the client
  • We have currently branded 50 of our delivery vehicles and are working towards branding more
  • We make use of cars for bigger deliveries, when available
  • Packaging: we are working on a better packaging solution to be implemented ASAP  
  • App Crashing when clicking “Share Bottles by PnP, get R50 off!” link on the order detail screen has been resolved in the latest version

Pick and Pay Bottles Grocery delivery – a review

PnP Bottles (bit of a weird name for a grocery app, I suspect they bought an existing app off someone else) is similar to the Checkers Sixty60 grocery ordering app, in that you can order online. Similarly to the Checkers Sixty60 ordering app, its also App only. Bleh!

PnP want a whole slew more personal info for sign up ahead of ordering, in comparison to the Checkers60 App though.

Score -1 for that.
There was also no indication of what they want to do with all my info.
I’m not stupid, its going to be sold to 3rd party marketers. A privacy policy should be provided _always_, especially if you ask for more than name/ address and phone number.
As PnP has a fairly substantive privacy policy published here –, I have emailed PnP’s Information Officer and asked them if this policy also applies to their Bottle App.
I will update this post when I have a reply. Regardless, currently it feels a little more intrusive than their competition.

Onto the App.
This is definitely not as well polished as the Sixty60 one.
There are a few UI issues (mostly related to the keyboard not dropping away when necessary, and scroll views not showing the full window).

Searching for items in the app is a little bit iffy. Results are a lot less relevant than in the Checkers60 app, and the selection of items seems a lot more limited. They do have specials in the app though.

Plus side – I can order a lot more groceries than the checkers app. There doesn’t seem to be an obvious mechanism for items that can’t be fulfilled, and doesn’t seem to be a limit on order size unlike the Sixy60 app.

Down side – delivery seems to be scheduled, and a lot slower – my order made at 10:40 can only be scheduled delivered between 2-3pm.

Firs delivery was actually made at 12:51pm.
This is over an hour earlier than the app delivery time –
While I appreciate an early order, this was slightly inconvenient, as I was planning to be out, and luckily happened to be home still.
Delivery times should be as scheduled, so you can plan around that.
Would be better to have an sms if you are going to deliver earlier (or later) than arranged.

The delivery unfortunately only included 3 bags of items – apparently the driver has to make 4 trips for all the items I ordered. Guess PnP need to do the same optimization that Sixty60 did (and limit orders), or use a larger vehicle for deliveries.

First issue – one item arrived unsealed / opened. Definitely a no-no, even more so in Covid times!

Driver was away before I discovered that, but as he’s on his way back 3 more times, I’ll see if he can return it with him.

I have gone through the submit a problem on the app (its prominently displayed on the order at least, unlike on Checkers60), but it says you may need to wait 2hrs! for a reply.
I think some points can be deducted for that.
To be honest, I’d want a reply immediately if there is an issue, and its during delivery hours.

Package arrived already opened from the PnP Bottle App order.

Approximately twenty minutes later, the next partial delivery was made.
Some good news – my motorbike driver has accepted the opened item, and will return / swap it. (see above image)

This time around, more bottles of sparkling water delivered (I ordered 48 in total). Driver has delivered a few bags worth this time


As an aside – not sure why they didn’t use a tuk-tuk, I’ve seen them before in the area.

I also feel quite guilty for the driver now as he has to make a bunch of trips, so intend to tip well (or at least more than I originally planned to).

Gratuitous driver shot –


Note the lack of branding on the delivery vehicle – this is in stark comparison to say Checkers, who have obvious branding. I would appreciate some sort of lanyard / identity card as well, so you can verify that the driver is indeed from the store before letting them in.

A subsequent 20 minutes later, the next delivery for the same order arrived (at 13:51pm)
What looks like the final delivery of everything has arrived.
One downside the PnP bags things came in are rather unusable, as they are taped together, and need to be ripped apart. I now have a ton more plastic waste.

This delivery unfortunately, has a completely different delivery driver, so I can’t tip the guy 🙁
Good news though, the opened package has been replaced (although somewhat gratuitously, that was sealed in yet another separate plastic bag).

I finally have what looks to be everything, and let the driver head back.

Well, I thought I did… I’m actually missing one of the bottles of sparkling water I ordered.
I have noted that on the App “Chat to us” in case of issues button, and am still waiting on a response.

Literally as I wrote that, I got a ping back from the app, and a response.
Apparently out of stock, and they’ll refund me.

Overall, my experience with PnP Bottles has been satisfactory, although much like the Sixty60 App, they really need to resolve or better work through their process management.

The Bottles App is buggy though, aside from the UI issues, I could repeatedly get it to crash by clicking the “Share Bottles by PnP, get R50 off!” link on my order detail screen.
I assume that they’ll fix those minor App issues though.

For the amount of stuff ordered, R35 for delivery was excellent value. Saved me going to the shops during Covid season, especially seeing as I could order a months worth of sparkling water at one time.

That said, the same exact issues that Sixty60 have, also plagues PnP Bottles.

– You need to check the order carefully on delivery to make sure of any issues.
– The drivers need to be better educated as to how to process returns or missing items.
– While the app has a better placed Issue with your Order – “Contact us” button, the timeframe for replies should be much faster. 2 hours for a reply is unacceptable during delivery hours.

My Score – 3 / 5

I’ve deducted 1/2 points each for –
– The buggy app
– For the excessive information required to register / privacy concerns.
– The drivers not wearing any sort of identification or proof that they’re a PnP Bottles delivery.
– …and for the delivery time not meeting the scheduled appointment time.

I’ll probably use this again, purely because I found the value in getting so many bottles of spring water delivered was worth it to me. I often go to the local PnP and find no stock.

Our local PnP (Longbeach Mall) is awful to shop at, I vowed never to go back after a previous bad experience [staff attitude & literal rudeness at checkout, bad service, and a manager who didn’t care / brushed me off when I reported the cashier and the packer].
I generally shop at other stores, or head to the Simons Town PnP branch, which although smaller, is a lot better.

Checkers Sixty60 Delivery – a review

While (or should I say when) I live in Cape Town, I do live in a slightly rural part, so don’t have much in the way of food delivery.
No uber eats, and the only junk food delivery is so-so pizza (Debonair’s).

Grocery delivery on the other hand seems to be picking up, as this last year – (referrring to 2020 – seeing as we’re barely into 2020+1), I now have two, yes two grocery delivery options.

Checkers Sixty60, and newly open for our area – PnP Bottles (to be reviewed in a subsequent post).
Both have similar costs for delivery – R35, and same day (or next day) delivery.

Checkers Sixty60
I ordered from Checkers Sixty60 last month. Annoyingly you can’t order from their website, only from their app. I find that a bit of a downside, they could easily replicate the functionality on a webapp (which is pretty much what their iOS / Android app is anyway).
That said, the app is actually quite good – signup is easy, searching for items is good excellent with fuzzy searching / result sets returned, and similar items recommended.
The UI is also fairly decent. I’m happy with it anyway, and I’m generally a cantankerous grumpy old man when it comes to dof decisions in app design.

You can only order a limited amount of items through the app – this ties in to be roughly what they can fit into the motorbike pannier / basket.

As an example of this – I could order 11 individual bottles of sparkling water, but no more.

My overall order experience was not as good as the app, which I’ll detail in a brief moment.

Ordering via the app was a breeze, and delivery was scheduled for an hour later.

Delivery wasn’t on time, but close enough. Delivery guy actually went past and drove off, so I had to run out and tell him to turn around.

Items were packed well – I’d actually say overpacked – the brown paper bags used could have been fuller. The bag quality is excellent, and will definitely be reused by me.

Delivery guy was friendly, but other than delivering items, had no way to process things like returns or items not ordered/incorrect. He was also clueless about anything other than ‘here are your items’. The delivery vehicle (a motorbike) was branded with the checkers logo on the sides of the back box. I forgot to note if the driver had any other ID on them to say “Checkers delivery staff”, but it was fairly obvious it was indeed a Checkers order.

One of my items got swapped out for another item. Luckily I caught that before the driver left, but there was nothing I could do in person. There was also no mechanism in the app for complaints or returns, and the delivery guy wouldn’t accept the wrong item to return, so I was stuck with it.

In retrospect, I could have checked don’t swap out items in the Checkers Sixty60 app, but its onerous to do this for each and every item in a shopping list. Their app needs to have a global option for that, or at least subsequently warn the buyer that a swap will happen prior to confirming the delivery.
None of that happened.

Delivery was free this time around, as I used a free delivery with your first order coupon.
While the majority of the order was correct, getting stuck with an item that I didn’t want, and couldn’t return soured me on the experience, especially when that replacement was double the cost of what I ordered, and not what I wanted.
That item also turned out to be melted into a gooey mess (but its been a month in the freezer since I ordered, and I don’t think I’ll be able to do anything about that now).

Lesson’s – check your order carefully and don’t let the driver leave until everything is counted and correct.

My score – 2.5/5 (see updates below for final score)

– The app side (for ordering at least) is excellent.
– I’ve deducted another point for the delivery size limitations, and another point and a half for lack of return procedures.
– The procedures need work, especially for complaints / issues, but I would use it again if I had better mechanisms for issues*.

I’ve subsequently gone back into my orders on the Checkers Sixty60 App.
(Orders / My Orders / Order #), and now see a Submit an Issue button.

I’m not sure if this is new to the App, as I looked all over the app previously for a complaint mechanism, and didn’t see it at the time, and there have been App Store Updates for the App. Either way, it needs to be far more visible / obvious.

The delivery driver had no clue about anything so couldn’t advise.
I suggest better training for drivers, and making this a lot more visible in the app. With that said, I’m going to return the 1.5 points I deducted, as this seems to be sort of resolved, although how the process will work I’ll have to leave to another order and update this again. I’m deducting another 1/2 point off for the UIX deficiencies though.

Updated Score – 3.5/5

Weep, for this is whats in charge of Nuclear Energy


I’ve uploaded a video of the Honorable Tina Joemat-Pettersson giving a speech at parliament.
I am strongly convinced that either she’s on drugs, or her speech writer is.

Sadly this is whats in charge of Energy in this country.

I weep for us.

Tesla Powerwall Payback Math for South Africa

The Tesla PowerWall is finally becoming available in South Africa, so I thought I’d do some “30% for math” calculations to work out payback periods.

This post is mostly inspired by the comments here –

Thanks to MacAfrican for the criticism in my comments, otherwise I’d be too lazy to do this post 🙂

Onto the math –

Predicted cost at the moment for a daily use PowerWall is $4000.
Rand is currently hovering at R16 (lets hope Zuma doesn’t open his mouth in the near future, as that historically has lead to large drops in Rand values).

Assuming R16 x 4000$, we have a cost of R64,000 for the battery itself.
Obviously thats a large sum of money.

Does it make sense / cents to buy one?

Lets have a look. First up we need to try to work out total lifetime costs.

The warranty for the Tesla on the site indicates this

The Tesla Powerwall includes a 10 year limited warranty.
The limited warranty covers defects in parts and workmanship, as well as at least 60% energy retention after 10 years, provided it is registered and used as intended.
The Tesla Powerwall is designed for daily use applications like self-consumption of solar and load shifting. Assuming full daily cycles, Tesla Powerwall is designed to provide energy for 3650 full equivalent cycles which is equivalent to 10 years of use.

Thats interesting, as it now gives us an indication of cycle usage.
From that, I can infer that each year we’ll see a drop of around 5% in capacity.

So year 2, we’ll see 95% of original capacity, year 10 down to 60% of original capacity, and at say Year 15, around 30% of original capacity. At year 15, I’d probably want to replace the unit, or have it as a secondary storage device..

With that in mind, we can do some math!

I’ve made a basic spreadsheet using those figures and worked out payback periods for the units.

I can’t predict Eskom pricing, so I’ve gone with current CoCT pricing per KW, and worked with annual % increase’s.
Total lifetime I’ve kept to 15 years, although you could probably scrape another year or two out of the units. I expect battery replacements to at least have halved in current Rand / Dollar terms in 10 years though, so replacement should be cheaper assuming Zuma doesn’t do any more Nene’s..

Below is what it looks like for a 5% annual increase

Screen Shot 2016-02-15 at 11.50.25 AM

You’ll see that it currently doesn’t make sense to use a PowerWall at a yearly 5% increase, even at a 15 year time frame. It comes close, but no cigar..

What happens at 10%?

10% increase

At a 10% annual increase (which might be closer to what Eskom pricing will eventually be than at 5%), we see breakeven in the 12th year of ownership. By 15 years we’re safely into profit.

Lets look at a best case – well, “worst case” scenario with a yearly 15% increase:

15% increase

15% annual increase see’s break even at Year 10.

Its unlikely that we’ll see continued 15% increases though, I guesstimate using thumbsuck that we’ll see continual annual increases of 8%, which leaves us breaking even at around Year 13.

Feel free to play around with the values, I’ve uploaded the Numbers file here (as I’m a larney Mac user), or as an Excel sheet here.

In other news, am fully expecting Rich from HomeBug to critique this, hehe 😉

Some points to note:

The Rand Dollar rate is going to be the main cost influence on whether the PowerWall makes sense. If the rand drops further (and the indications are that it will), then it doesn’t make sense at R20/ dollar. If by some miracle the rand recovers to say R14 or R12 to the dollar, buying a PowerWall is a no-brainer.

NERSA approved increases may or may not beat my guesstimates. Historically we’re much more expensive per KW than 10 years ago by a large factor, so its likely that a moderate value of 10% increase per annum is going to correlate with actual figures. This will also increase once Eskom/ Muni’s introduce further daily connection fee’s and other non tariff increases on top of per KW pricing.
(Actual historical figures can be found here – )

I don’t calculate round trip values for Electricity in /out of the PowerWall. Tesla documentation indicates that this is 92%, so final KW generation figures probably should be discounted by 8% for further accuracy.

I also assume you’ll be generating electricity to go into the unit from a solar install. Costs for that are not included, as we are looking purely at the viability of the PowerWall. While I can do full system calculations, its already clear that Solar generation is already cheaper than Eskom in South Africa, and has been for a few years no. Rehashing that again is of no interest to me.

Being efficient – Roof insulation – keep it cool in summer, and hot in winter!

Energy efficiency is something everyone can aim for – its typically only a minor expense and long term you save. Heck, given our electricity costs, short term we save!

Today, I look at roof insulation.

In Cape Town, we have hot summers, and coldish winters. Sure, it *feels* cold to us, but I’ve spent many a winter in far colder places.

The worst being Harbin at -40c!
I can safely say:
#1 it does freeze before it hits the ground.
#2 don’t eat the yellow snow 🙂

Back to warmer climes though –

SANS Efficiency rules (SANS 10400-XA) recommends an R value of 3.7 for insulation in Cape Town homes. (This is over and above the typical R values for roofing).

See below graphic for an indication of R values (required insulation for SA)
climate zones sa

Whats an R value, I hear you ask?
An R value is the capacity of an insulating material to resist heat flow.
The R is for… resistance.

On average:
A roof typically has an R value of 30.
A brick wall an R value of 19.

The higher the R value, the less you lose to heat.
Obviously in winter, we want to ensure that the R values for the house are high, so that we don’t lose any heat. Adding insulation to improve the roof R values is a no brainer.

What about summer?
As everyone knows, heat rises.
Surely insulating the roof prevents that heat from escaping?

Yes… However, what most people don’t think about is that although heat rises, the entire roof is also a heat sink.

Go into the roof in on a summer day. How much hotter is it than the rest of the house? Heat rises, but most of the heat is from the sun to roof, not rooms to ceiling.

Think of it this way –

The sun is above.
The roof is above.

Most roofs are made from metal or tile, those absorb a lot of heat.

The thing thats going to get heated the most is the roof area.
Insulating that will prevent a lot of the heat coming in from that area.

Heat does rise, but the majority of the additional heat in the home is generated from the roof in summer, not the rest of the house.

So, what to do?
That same insulation that helps us keep the house warm in winter helps us in summer. Insulating the roof prevents the heat from the roof area getting back into the house.

But…. what about the heat in the roof from winter? – don’t we want that?
Yes, we do, but keeping the rooms to a stable temperature is more important.
We live in the rooms, not the roof, so we want to keep the rooms as stable a temperature as possible. Insulating them top (ceiling+insulation), bottom (floor), and sides (walls) makes that happen.

Ok, so getting insulation makes sense for both winter, and summer. What should I buy?
Going back to the SANS values per region, we have a recommended number for insulation values.
Note: That number is a *minimum* not a recommendation. Your best bet is to always exceed the minimum where it makes financial sense.

So, again Cape Town has an recommended R value of 3.7 for roof insulation.
What that means in people terms is that for effective cooling / heating, Isotherm or similar insulation needs to be about 135MM or so thicker to exceed that value.

What insulation should I get?
There are a couple of readily available options:

Isotherm (Plastic based)
My personal choice is to recommend Isotherm for insulation. Its basically plastic, so is harmless to work with, and it won’t degrade like other products. Its really easy to work with too. It doesn’t have issues with water either, so is less of an issue with leaks. DIY’ing a roof install with it is fast and easy too. The rolls are light and it pretty much lays itself out when you unroll it. Once again, remember that our Cape Town R value is 3.7, so a minimum of 135mm is recommended. Again, if you can afford thicker rolls do it.

Think Pink (Fibreglass based)
While this offers marginally higher R values than Isotherm, its a pain to work with.
If you’re getting a professional installer to do it, then this is your choice, if you’re DIY’ing – avoid. Needs face masks, and gloves, and makes working in the ceiling space annoying afterwards as the fibreglass gets into your skin. Downsides – its a little worse than Isotherm with regards to water, but nowhere near as bad as cellulose.
Again, recommended thickness is at least 135mm for Cape Town.

Blown paper/ cellulose
(Just say no)
This is usually the cheapest solution. Usually its blown into the air space with a blower and the benefits are that its extremely fast to install. You need to put down at least 3-4 inches though. There are major downsides – while it offers moderate R values initially, it does tend to settle, and the R values reduce somewhat after a few months. It also has bad issues if there is a leak, as it absorbs the water, and the resulting weight can collapse the ceiling boards. Lots of examples of that on google images.
Lastly it also gets everywhere – you’ll be finding bits floating down for years to come.

Other fun solutions
Paint the roof white, as this is the most reflective color.

Mount solar panels, and kill 2 birds with one stone – my roof is partially covered by solar panels, this helps, as they’re mounted above the roof, and keep the underlying area cool, plus generate electricity. Its a little more expensive than roof insulation though!

Install those roof mounted twirly extraction fans, as those help drawing the hot air out.

Further reading: – Rather good US Gov Document on this topic.


I’ve “almost” completed my house in Noordhoek, and its completely offgrid power-wise.

Currently I have 6 x 300W panels, 2 x 220Ah GEL Lead Acid batteries, an FM80, and a Victron 3KW Multiplus running, which gives me about 2KW of usable battery +- in 16 hr period, or in easier to understand terms – about 125W / hr of usage outside of daytime.

Panels come in from the roof, in 2 strings of 3 panels each.
The FM80 can support 150V / 64A input max, so I have to put 3 panels max per string for safety reasons.
36V x 3 @ 8A x2 / 108V /8A per string.
For a 108V / 16A into the FM80.

This then comes out of the FM80 to a 24V battery bank.
The FM80 charges the in the early mornings, and keeps it topped up during the day if necessary.
The 24V battery bank is connected to a Victron Multiplus 3000/24, which then provides AC out to the house.

Batteries are 24v / 220Ah (5280W total capacity). 12v / 220Ah in series to double the voltage to 24v.
Usable capacity is 2600W overnight assuming a 50% discharge.
Overnight I actually use less than 1KW or so, so I discharge to about 80% overnight from a full battery.
Thats a 20% daily DoD, which should give me a decent lifetime.

This isn’t much!
Obviously the limiting factor here is storage (batteries), as the panels can generate far more than is needed to recharge the batteries or run the house.

What does my house need anyway in terms of power?

Lighting is all filament LED, so is minimal
Kitchen = 5 x 3W
Bedroom = 1 x 8W
Bathroom = 3 x 3W

32W inside with all the interior lighting turned on.

Hot water is provided by a solar geyser.
I’m not planning on supplementing the hot water with electricity to heat in winter unless I need to shunt excess power out from the solar panels at the inverter, so thats zero usage.

Despite the complete lack of information on most websites regarding power usage for Fridge / Freezers, I’ve decided on this model – Bosch KGW36XL30

It claims to use 227 KWhr/year, so thats about 620W /day (or 25W / hr), which is quite reasonable.

Its R7,000 though, so not cheap!

Useful site for checking KW ratings here –, as most of the manufacturer sites are useless.

Gas oven / hob setup, so zero power usage (SMEG 60cm unit).
Electric Kettles, and toasters are a no-no, as they suck too much juice.

Washing machine should use about 1-2KW a wash, so can only be run daytime when there is sun.

LED TV should be fine, as they’re about 50-70W on average.

Not much headroom for other electronics, but its sufficient for the basics. When I make more money, I can ship over the Lithium batteries 🙂

Tesla’s Powerwall

As there is a lot of interest on Tesla’s Powerwall, I thought I’d collate what I could find out about it.

The official press release details are here – and the end user details here


From those pages we can glean this:

Mounting: Wall Mounted Indoor/Outdoor
Inverter: Pairs with growing list of inverters
Energy: 7 kWh or 10 kWh
Continuous Power: 2 kW
Peak Power: 3.3 kW
Voltage: 350 – 450 volts
Current: 5.8 amp nominal, 8.6 amp peak output
Round Trip Efficiency: >92%
Operating Temperature Range: -20C (-4F) to 43C (110F)
Warranty: 10 years
Weight: 100kg
Dimensions: H: 1300mm W: 860mm D:180mm

There are 2 different Powerwall units available:

10KWhr for weekly cycle use @ 3500$ to installers.
7KWhr for daily cycle use @ 3000$ to installers.

Up to 9 units can be chained together to provide more power.

Simple math for the given values shows that the continuous / peak sort of make sense –
350V @ 5.8A = 2030W +-
350V @ 8.6A = 3010W +-

The voltage is curious though – at that sort of voltage, it means you will be connecting to a hybrid grid tie inverter rather than a battery inverter. Most commercial battery inverters run at 24/36/48 (or other higher multiples of 12), so that eliminates using those (if the voltages are correct).

The press pages do mention that the Powerwall is supported by the Fronius Symo Hybrid inverter.
The datasheet for those is here –

If we take a look at that, we can see that they only seem to offer a 3 phase solution currently, and that it talks to batteries using Modbus RTU, and at various voltages, depending on capacity.

Fronius’s 10.5KWh unit offers 8.4KWh capacity (80% DoD), and connects at between 280-400V @ 16A, so would be the closest offering they have to the Tesla Powerwall. Its also about twice the price!

There is other data out there though. This page purports to show details of TESLA’s 10KWhr unit.
(pictured below)

Screen Shot 2015-05-04 at 5.36.30 AM

That unit (if its real) looks a lot more compatible with battery chargers as it runs at a more common 48v.

What batteries are they using?
Tesla are using NCA batteries (LiNiCoAl)- Lithium Nickel Cobalt Aluminum in the Powerwall 10KW (weekly cycle unit)

Tesla are using NMC (LiNiMnCo) in the 7KW unit.

Elon Musk – quoted from the recent press conference:

The 10kWh device is designed as back-up, suitable for 60-70 cycles per year. Its chemistry is similar to the Tesla Model S electric vehicle, and is nickel-cobalt-aluminium cathode.

The 7kWh system is designed for daily cycling – when homes and businesses will store solar electricity produced during the day. Its daily cycling control constituent is nickel-manganese-cobalt, and Musk expects it to daily cycle for “something on the order” of 15 years.

“Actually the warranty period would be a little bit less than that,” Musk said.

“But we expect it to be something that’s in the kind of 5,000 cycle range capability, whereas the high-energy pack is more like around the maybe depending upon on how it’s used anywhere from 1,000 cycles to 1,500 cycles. And they have comparable calendar lives, and for the high energy one, it’s important to appreciate that this actually has a lot of interest from utilities “

What actual capacity is the 7KWhr unit? (daily cycle)

 Option 1

The 7KW unit is really a 10KW unit, and they’re running it at 70% of actual capacity.


Lifetime for NCA is in the 10 year range (3000 cycles +-) @ 70% DoD (depth of discharge) before it drops below 80% of original capacity.

Lithium doesn’t like being 100% charged, and it doesn’t like being 100% discharged.
Data sheets indicate that Lithium prefers 15-85% for longer lifetimes, so thats the “sweet spot”.

 Option 2
It might be that the 7KW unit is only 7KW storage though, which means actual capacity is really 70% of that or just under 5KW (4.9KWhr usable).

I personally think that its going to be option 2, sadly.

Why the cooling?
Lithium and other battery lifetime is extended dramatically if you keep it cool.
I’ll assume for lifetime purposes they’ll try to keep the batteries down to 25C

Why is it a game changer?
Pricing is about half of current retail battery units.

…but Lead Acid is cheaper!
Lead Acid isn’t cheaper.

Lead Acid provides about 30% usable capacity for a battery.
Lithium provides about 70% usable capacity for a battery.

So, if you need 10KW of usable storage, you need
30KW of Lead Acid
14KW of Lithium

Lead Acid will take up far more space.
Have less lifetime.

Whats the difference between the 10KW unit and the 7KW unit?
Other than the sizing / cycle usage, we don’t know (yet).

10KW unit is rated for weekly cycle, so would probably be for UPS style usage – eg to assist with grid outages like Eskom’s regular ones. Given Eskom’s reliability though, the 7KW unit may be more applicable here!

7KW unit is rated for daily cycle, so would probably lend itself to off grid, or time shifting, or if power outages get to be regular day to day outages here; ideal for that.
South Africa doesn’t currently have time of day rates for residential end users, although thats coming at some point, so time shifting isn’t useful here (yet).

Some thoughts on this –
If the 10KW unit is rated for weekly discharge @ 10 years (3650 / 7), thats gives you roughly 500 cycles.
500 cycles for NCA batteries @ 100% DoD is the rough lifetime, so it looks likely that 10KW is actually 10KW.

If the 7KW unit is rated for daily discharge @ 10 years, thats 3650 odd cycles. 70% DoD for NCA batteries gives about 3500 cycles before it hits 80% of original total capacity, so would indicate that the 7KW unit probably is going to be 4.9KW usable, as that also matches with the lifetime / usage.

Their pricing points for the 2 units sort of confirms it – 10KW @ 3500$, 7KW @ 3000$

So, my guess is that the 7KW is going to turn out to be 4.9KW usable out of 7KW actual storage.

Some real life testing for the NCA battery tech Tesla uses here –

What do I need to use a Powerwall?
At a best guess, it looks like its intended to be used with a hybrid inverter.
A hybrid inverter is a grid tied inverter with battery charging capability that can create a “mini house grid” if Eskom goes off.

So far Tesla says it works with the Fronius Symo Hybrid inverter.

Assuming that there really are a number of different units, it looks like they may offer a 48V version for those with existing MPPT chargers (as per the graphic up above somewhere).

Fronius’s Symo Hybrid inverter uses Modbus RTU (over RS485 – serial) to talk to its batteries, so I would expect the Powerwall to support that (amongst other things)

The (alleged) data sheet says IEC 61850 ( )

Tesla has also been advertising for staff who have experience with RS485, Modbus, IEC 61850 and DNP3

IEC 61850 is the european favoured smart grid standard, DNP3 is the american standard.

Support for those is more likely to be in place for Tesla’s larger units eg the 100MW and up options.

Whats the price likely to be in South Africa?
If one counts in duties, clearance, shipping it will probably be in the 5000$ range or R60,000 for the 7KW.

I’ll try to keep this post updated when more info comes out.
Feel free to ask questions in the comments.

Eskom / Municipality vs Solar pricing Maths.

One of the age old questions I get asked is this – Does solar make cents(sic)?
The smartass answer is of course “it depends”.

Eskom is fast turning that answer into “extremely well” though.

Looking at the math, the average household with say 1100KW usage a month or R1800 a month average bill in Cape Town pays these rates:

600KW @ 1.56 = R936
500KW @ 1.86 = R930 (over 600KW is billed at higher rates)

Monthly thats R1866. Lets round that down to R1800 for ease of use.

1100KW / month is 36KW / day.

36KW daily usage = 1.5KW/hr on average. Ouch.

That’s quite high. Lets bring that down. We did.

First steps

Install solar hot water heating for hot water (and pool heating if you have a pool).

That should bring our bill down about 40-50%, as heating water is a major consumer of electricity.
Install gas for cooking. (We didn’t as we don’t cook that often, and it didn’t make sense in our situation)
Install LED lighting instead of power sucking halogens and regular bulbs.
We should be looking at closer to 20KW day now.

You’ll probably have spent up to R30,000 on that.


Lesson #1
Its ALWAYS cheaper to first reduce costs before going solar.
Our best bang per buck is *always* to reduce our monthly usage first.

In our case, we installed 2 x 150L solar hot water heaters.
Replaced *all* the lighting with LED’s. Don’t forget the outdoor security lighting!
Our gate light was on 12hrs a day. We replaced it with 10W LED lighting.

Outdoor security lighting @ 10W /hr @ 12hrs vs Halogen @ 150W @ 12hrs= *major savings*.
eg 120W usage for 12hrs, vs 1800W!
One 10W LED run for 12Hrs a day = 120W = (monthly 30 x 12Hrs) = R5.4
One 150W Halogen run for 12Hrs a day = R2.7 a *day*, or R81 a month.

Imagine that for all the lights in the house. If you have Halogen downlights get rid of them, and get LED ones. Takes less than a month *per* bulb for payback time…

After all that, our electricity usage went down from 1100KW/ month to about 600KW month.
That’s a 3 year payback on investment if it’s similar to our R30,000 cost.

Sure, but thats got nothing to do with Solar I hear you say.
Well, yes it does. Again, *reduce your footprint* first.

Second steps

Install some PV!

180k will get the average house with 20kw daily usage offgrid including batteries in todays money.
(Say about 5kw panels on the roof, and 30kw of battery, plus a 3kw backup generator to cater for repeated winter outages past 2 days of no sun, and all inverters etc for a single phase household)

Some Math / Justification on that
20KW daily usage = 830W/hr on average.
5KW panels will generate over 15KW in winter, and well over 30KW in summer daily, so deficit is 5KW/day or zero in summer.

Assuming 5KW / day worst case scenario deficit
You need roughly 3 x (3 days of battery) x 2 (50% discharge) for usage.
– Batteries shouldn’t be drained past 50%, so halve the rated value.
– Cater for 3 days of worst case scenario of no sun.
– Add a generator for generation for worst case scenario getting worse, and batteries go below that point of discharge.

With that in mind, deficit is 5KW odd in winter, so 3 x 5 = 15KW for 3 days of discharge (say 3 days of cloudy weather) x 2 (can’t discharge lead acid/agm/crystal batteries more than 50%) = roughly 30KW required in batteries.

28.8KW of battery can be had for a little over R1/Whr eg / 20x12v@120Ah= 28800W which can be run in 24V or 48V easily (battery inverters usually run in 24v or 48v sizing)

12v@120Ah Gel Lead Acid is currently R1500 at retail, or less, which = R30,000 for 28.8KW per 5 years usage worse case.
The good news is that battery prices are headed down, not up.

5KW of panels looks like 18 panels * 300W
300W panels are in the R11/w range retail, so roughly R60,000

Panels + Batteries = R90,000

MPPT PV Inverter should be about R20,000 (or less)
Mounting + 3KW Generator say R10,000
DC -> AC Battery inverter about R20,000 (or less), oversized so that the system is scalable if necessary.

Total so far – R140,000
Add installation, say another R10,000 (1-2 days of work) and replacement batteries in 5 years, and you’re looking at closer to R180,000 for an offgrid system over a 10 year lifespan.

If you start looking at that over 10 year terms, that’s a lot more affordable, even if you cater in replacing batteries every 5 years.

Our monthly bill is only R1000 a month though at 600KW usage / month. (Usage of R936 + other costs), and R180,000 is closer to R1500 a month. There’s a big discrepancy.

R1000 a month for 600KW x 12 = R12,000
R12,000 x 10 = R 120,000.

Our costs are closer to R180,000.

Sure. It doesn’t make sense. Its 50% more expensive!
However, that’s at todays pricing.

Nersa has granted Eskom a 15%+ increase (and Eskom is asking for more now, as the situation is dire).
15% increase on Eskom pricing means that Year 2 monthly rates are now R1150 for our 20KW/day usage.
The municipality is likely going to add a few % on top of that also, as they’ve asked for 7% also (also to be confirmed).

So year one is R12,000/ R1000 monthly
Year two is R13,800 / R1150 monthly (15% increase, which is looking lower than the actual increase will be).
Year three is R15,180 (assuming a meagre 10% increase on year 2), and so on..

Guess what just happened – our costs have (not so magically) equalised with our investment, and fairly quickly at that. Without guessing whats going to happen for year four to year ten, its already looking like a smart decision to have gone solar. We also have a nice equity in a system that has increased our house value, AND we have a system thats more reliable than Eskom is.

I know we’re happy paying a premium for the first year or two just to have electricity 24/7.

Essentially, if you have a R1500 bill a month in electricity now, and you have the capital, and roof space for it, its roughly time to start looking at going completely offgrid, as it will payoff by the 10 year mark.

I’m happy paying that premium to have reliable electricity in house right now, and I’ll guarantee you that the costs will be cheaper for self generation based than you are billed for electricity within 5 years.

Footnote –
You’ll note that I haven’t looked at feeding back to the grid in the above scenario.


It doesn’t make financial sense (at least for Cape Town). I’ll leave it up to the reader to discover why, and do the math (or look at the comments on previous articles where someone did the math!).