CapeInfo’s Smarter Living Project started off to determine what one really needs to go off the electrical grid — is it  as expensive as  people say or, if one adapts one’s lifestyle, is it affordable or… even cheaper.  Off-the-grid in this case meant no external electric sources at all — no Eskom, no municipal connection.

Cooking was done using gas and hot water was heated by a cheap solar water heater, supplemented by a hot water/space heater in winter using firewood.

Very early on, I wrote a story on the Ekanini iShacks outside Stellenbosch, where over 1,000 ‘shacks’ in an informal settlement had been converted to solar power.  I am in awe of that initiative.  Let’s make that mainstream.

“You can’t manage what you can’t measure”

I installed everything myself and have never done anything like this before.  My installation was, however, connected to the house’s electrical distribution board by the farm’s electrician, and used all the house’s existing electrical reticulation.

My first (very stupid) mistake was the connection to the solar panel.  After a few days, I discovered the single battery wasn’t charging.  So I bought a second battery while the first was being checked.  Buying a simple multimeter, I discovered my connection at the solar panel was the fault.  That multimeter proved its worth as my only measure for a long time.

At the suggestion of someone at Stellenbosch University’s Centre for Renewable & Sustainable Energy Studies, I obtained an Efergy (branded by Ellie’s in SA) Solar Hub.  After weeks of frustration and the worst customer support I’ve ever experienced, I discovered that it simply can’t measure 12 Volt power.  (I think they’ve rectified this but I haven’t had any response to emails.)

Then, rather late in the day, I discovered that my Victron Power Controller is compatible with their Bluetooth VE.Direct Smart dongle (R588), which plugs in the Controller and gives realtime information about the panels and batteries on my phone.  I wish I had this from Day One!

I don’t know how much difference there is between the various brands of premium panels but the one thing I have seen is the drop in panel prices since this project started.  The two 150W panels used up to know cost R1,710 each.  I can now buy GCL-P6  330W panels for R1,819, and Canadian Solar 355W panels for R2,090.  So prices have halved.

I did put some effort into maximising the power generated by allowing the panels to tilt according to the seasons.  That story is here.  It was evident from the start that getting through summers wasn’t going to be an issue, but winters would be a challenge,

This converts 12 Volt DC electricity to 220 Volts AC. I  started off  using an old 300W inverter (bought for R500 in KZN to charge my laptop from my bakkie’s battery while staying at an off-the-grid lodge).  It worked well for lights, laptop, Wifi router and cellphone charging, but wasn’t sufficient for the fridge because of the power surge when the compressor turns on.  So an 800W inverter took its place pretty quickly.

“But you can’t use a modified sine wave inverter!” I had friends saying, “It will damage all your equipment.”  The TES inverter cost R1,140 and the alternative pure sine wave inverter suggested was a Victron Energy Inverter Phoenix Compact 12V 1200VA for R8,393.

There are no sensitive electronics in the fridge I have, and my laptop’s power is filtered by its charger, so I couldn’t foresee any problems.  And haven’t experienced any over the 2½ years.  It’s time to upgrade that inverter, both for more power and cleaner current to power, for example, a washing machine which does have a lot of sensitive electronics.

Without a hot water geyser and electric stove & oven, the actual power demand is not that high.

What was I using? (Laptop & fridge use optimised)
ApplianceWatt/h (max load)Daytime use WhNighttime use Wh
Laptop & wireless router4536070
Charging cellphone; cameras; power drill; etc.18360

The total maximum demand — if all appliances are turned on at the same time — is only 120 Watts, excluding the power surges from some appliances.

  • This system was never intended to cater for appliances like a large microwave, hair drier, vacuum cleaner, etc., which each use more than 1000W or even small electric heaters.
  • Miscellaneous appliances such as toaster; small microwave; blender; etc. were used too rarely to be included in this table.  But they did work,
  • A better inverter will use 60% less power than the one I used.

I honestly believe that the only way anyone can justify buying a Tesla Powerwall is if they are a committed “early adopter” of new technology, and that the Powerwall is going to be a conversation piece in the living room.

Conventional lead acid batteries and hybrid batteries do as good a job, at a fraction of the price.  Long term investments in rapidly-changing technologies is a waste of money.  From 2022 — four years away — we will see a revolution in battery technologies with the introduction of solid state batteries, with higher charge densities and fast charging times.  Both Volkswagen and Toyota are committed to new electric vehicles using these batteries by then.

Nissan opened a battery-recycling factory because they replace EV batteries when they reach 80% efficiency — the vehicle’s driving range is its most important feature.  They replace the dud cells with new ones and resell the battery packs for domestic use.  In Japan, a 24kWh battery pack costs 300,000 Yen (R42,000 at R0.14=JPY1).  A 24KwH Li-ion battery pack in SA will cost about R130,000.

What I have learned with the lead acid batteries I’ve been using is the importance of never running them flat and trying to always keep the charge above 50%.  Yes, you can use much more of the charge with lithium ion batteries, but you pay much more.  Battery weight and bulk is critical for mobile devices and electric vehicles, but not at all for houses.  The heavier the battery, the more difficult it is to steal.

I’ve also seen the importance of a proper enclosure for the batteries.  On cold winter mornings, the batteries lose a lot of capacity.  In the next phase of this project, the batteries will be supplied with some warmth on icy days.

The Laptop
The first thing I realised is that this is not a normal domestic test.  This house is used as an office and a home. An empty house would spend the day recharging the batteries for the night.

Habitually, I turn my laptop on when I wake up and turn it off when I go to sleep.  It can be on for 17 hours a day.  That was the first habit I changed.  Just closing it when I’m not using it — putting it into sleep mode — made a big difference in consumption.

Before I became laptop-conscious, I was using over 1000Wh a day — by far the biggest single appliance-user.  It can be equated to leaving a TV set on all day.

Apart from putting the laptop to sleep more often, changing the hard drive for a solid state disk, upgrading my phone and doing more on the new phone wasn’t only more convenient, it saved even more power.  And it’s great for watching movies!

Now if I had a Lenovo Carbon X1 laptop, with a battery life of up to 15 hours, that wouldn’t be a problem.  Its selling price of R40,400 is a problem!

The fridge
The fridge has its own story.  It’s a 150 litre Hisense with a rated consumption of 155kWh/year — that’s 425Wh/day or 18W/hour — very low by fridge standards  The reality is that the compressor motor turns on about three times an hour for several minutes, using a paltry 35W.  But… and it’s a very big but… I have seen very short spikes of 860W when the motor turns on.  At nighttime, that’s a battery killer… or, at best, the quickest way to shorten your battery’s life.

So, during winter when my power supply was stressed, I took a leaf from the book by Indian shopkeepers.  Being as parsimonious as they are, they habitually turn the mains switch off at night when they leave their shops to save electricity.  Of course, this turns all fridges off too.  So, in addition to the unreliability of Indian power supplies, this is why Asian fridge manufacturers were among the first to introduce emergency ratings — the number of hours a fridge stays cold without electricity.  Today, many freezers or fridges have 24 hour ratings.

Not so my Hisense… so I packed a big part of the freezer with refreezable ice bricks, since I rarely buy frozen products.  And that worked.  Turning the fridge off from 9pm to 9am in winter, it still managed to stay cold enough. Of course, you can’t do that if you have separate freezer and fridge sections.

There are inverter-friendly fridges on the SA market — where the compressor remains on all the time — but they all use more power than a top-end, standard fridge.

The best solution is also much more expensive.  A 260 litre A+++ Miele fridge/freezer (R29,000), for example, only uses 174kWh or 0.474kWh per day — not much more than the much smaller Hisense.  It’s power surge is minimal and the storage time if power is switched off is 24 hours.

The First Purchases… and the First Winter
Victron MTTP 75/15 controllerR1,200
TES modified sine wave Inverter 800WR1,140
2 x 102Ah deep cycle lead acid batteryR3,400
1 x 150W PanelR1,710

Verdict for the end of the first winter:  150W of solar panel was just not enough to fully charge the two batteries.  There were several days when I had to take one battery away to be charged.  In a normal domestic situation where there is very little consumption during the day, and the panel just charges the batteries, this would not be a problem.

There were a few days when I used the bakkie’s battery to power the house — which didn’t shorten that battery’s life significantly.  (It did last 5 years and finally died when the buzzer reminding me that I’d left the headlights on stopped working!)  This does make the case for a mobile powerbank that can be remotely charged.

Cost of electricity: This assumes that the panels, controller and inverter have a life span of 20 years.  The batteries proved to have a lifespan of 18 months.  It’s a simple sum that doesn’t take into consideration interest charges.

The Cost of Electricity — First 18 months
ItemCostLifespanCost per month
HardwareR4,05020 yearsR16,80
BatteriesR3, 40018 monthsR188,29

The Second Winter
2 x 150W PanelsR3,420
Victron MTTP conttrollerR1,200
TES modified sine wave Inverter 800W,R1,140
3 x 102Ah deep cycle lead acid batteries @R1 700R5,100

Verdict for the end of the second winter:  I had bought an extra panel. There were only two days when I actually ran out of power, and the two panels were able to charge the battery quickly enough that I never had to resort to remote charging.

Cost of electricity: The single battery is still going strong 20 months after I bought it, although it is being used alongside two new batteries.  I assume its longevity is due to the fact that the extra panels meant it was discharged totally less often.  In the figures below, I’ve assumed that would have died after 24 months had it been on its own.

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Verdict for the end of the third winter:  I bought two extra 102Ah lead acid batteries to supplement the existing one.  My battery usage rarely dropped below 50% (12.20V) and the discharge table from the battery manufacturer shows that these batteries should last about 3 years.  In spite of a very wet winter, I’ve never been able to get even close to exhausting the batteries.

Cost of electricity: Power security comes at a small cost, compared to the previous winter.  I wish I had rather bought Omnipower Hybrid batteries which would have seen costs much lower.

The Cost of Electricity — Through the Third Winter
ItemCostLifespanCost per month
HardwareR5,74020 yearsR23.92
3x102Ah Lead Acid BatteriesR5,10036 monthsR141.67
The Cost of Electricity — The Better Option>strong>
ItemCostLifespanCost per month
HardwareR5,74020 yearsR23.92
2x180Ah Hybrid Batteries,7 444,12 years,51.69
id Batteries
R7,44412 yearsR51.69

I will be testing the Omnipower Hybrid batteries next and they promise to offer far longer life, making them the most economical bet.

Battery capacity
BatteriesTotal stored kWhTarget max. to prolong battery life kWh
1 x 102Ah lead acid battery1.2240.612
2 x 102Ah lead acid battery2.4481.224
3 x 102Ah lead acid battery3.6721.836
Power Generation — 2 x 150W panels
Best sunny day1.34
Average rainy/overcast day0.89
Very worst dark/overcast day0.23

There has been about 2 hours on 2 days in different years when it was too dark for the panels to generate any electricity.  Many rainy days are still bright, and generate almost as much electricity as the sunniest days.  Dark weather very rarely lasts more than 36 hours.

Since this project started, I’ve generated 765kWh of my own electricity at the time of writing.  That feels very good!  🙂

The next phase will generate up to 5.6kWh/day and be able to handle anything I can throw at it… far more the normal house scenario at a cost of R183/month (using the same methodology as above).  There will also be a ‘mobile Powerbank’ to provide added security during the worst of the winter months.  You’ll have to come back to read about that!

A note for Employers

I’ve been approached by scores and scores of farmworkers asking how they can go the solar route — like the community in Ekanini.  You can help them.

Municipalities get tied into loans/grants from Eskom to provide expensive township infrastructure, which ties them into even more expensive electricity.  The cost of the infrastructure doesn’t warrant the small amounts of electricity provided.

Maybe someone will tell me if the capital costs of PV panels, controllers and batteries can be written off against tax by employers?  Because a simple 12 Volt solar system would cost something like this:

A Simple Solar System
ItemCostLifespanCost per month
1 x 330W Solar PanelR1,81920 yearsR7.58
1 x controller with 12V outputR50020 yearsR2.08
1 x 180Ah Hybrid Battery,R3 722,12 years,R25.85R3.72212 yearsR25.85

In 2016, Stellenbosch Municipality was paying the Sustainability Institute R60 a month per household — the value of the free basic electricity subsidy for those connected to the Eskom grid.  All municipalities should be paying that amount for all solar-powered dwellings.

Do the sums, add interest charges, explore the tax benefits and harass your municipality for the free electricity subsidy…   This could be the biggest perk employers can give employees who live without electricity, or want to get off the Eskom system.  #LoyaltyRewards

One Response

  1. This is a great article, very well researched and taking into account the capital costs and lifetime years of the products… well done! I am impressed. Now, we just need to get this into an infographic manual for home users 🙂

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