Opinion by Teresa Settas, Marketing Director of the One Energy Group
Many people are looking for back-up power solutions for their homes and businesses to see them through unpredictable and productivity-killing Eskom load shedding and are also fed up with the rocketing costs of electricity that Eskom cannot reliably or affordably supply. The parlous state of municipalities should also be of great concern, with collapsing infrastructure, non-existent service delivery and rampant cable theft that leaves you without power for extended periods of time, compromising your productivity, safety, security, income and quality of life.
Before you rush into purchasing a back-up power solution, you need to take a considered and long-term view of how to get yourself as close to grid independence as possible, for the long term. It’s crucial to consider where South Africa’s energy future is headed, and what this means for your home and business. Any money spent on an unsuitable back-up solution today detracts from your ultimate objective of grid-independence and self-sufficiency. Don’t be lured into the many cheap ‘plug and play’ solutions being punted on the market by drop-and-go shippers and dodgy installers who offer no back-up or support in country, and even less in terms of warranties on their products.
Start with a scalable, quality solar PV hybrid solution that takes care of your immediate needs for back-up power during load shedding and power failures and allows you to scale up in future to self-generation by adding solar panels and additional batteries if needed. While you can start initially with your hybrid system configured as a back-up solution (inverter and battery only), as budget allows you will be able to expand with solar panels to generate your own power, providing back-up and saving you a fortune in electricity costs. The big caveat here is that not all inverters offer this scalable functionality, so it’s essential to work with a renewable energy partner who is experienced in this field and understands and works with your long-term objectives. Avoid at all costs the cheap, quick fixes sold by bakkie brigade newcomers to the industry looking to make a quick buck on SA’s energy crisis.
This is how you start your journey to greater grid-independence step-by-step
Step 1: Convert your electric geyser to a solar geyser
An electric geyser accounts for 30-40% of your monthly electricity usage in a typical mid-income home, so this is the most crucial starting point to reducing your daily electricity load, and which means you can also buy a smaller and more affordable PV solution. A 200-litre solar geyser, fully installed is around R27 000. On a R3000 electricity bill, you’ll save around R880 per month, amortising your outlay in just over two years (28 months) without taking annual electricity cost increases into account.
Step 2: Start with a hybrid inverter and li-ion battery solution that is expandable with panels and more batteries
As your budget allows, you can add solar panels and additional li-ion batteries to provide you with a full hybrid system for self-generation, electricity savings and battery-back up. For purposes of this illustrative exercise, we used a Sunsynk inverter configuration, however there are also other quality Hybrid inverter solutions available. Don’t get duped into cheap inverters and outdated lead acid battery technology and installations as these entry level products simply don’t offer this scalability or reliability. They also simply will not cope with the demands of stage 4 and 6 load shedding which we have been experiencing of late.
Option 1:
- Install a 5kW Sunsynk inverter with one 3,6kWh li-ion battery set up as a UPS config initially – this means it will provide back-up for your essential loads (which we split at your DB board) during loadshedding and power outages only. Starting cost is around R78k including professional installation and all the required electrical protection and a COC.
- If you need a bigger inverter, then go for a Sunsynk 8kW Hybrid Inverter & 7.2kWh li-Ion battery. Set up as a UPS configuration initially. Expandable with solar panels and additional batteries. From R122k.
Option 2:
- Install a 5kW Sunsynk inverter with 7,2kWh li-ion batteries and a 2.7kW solar array. Starting cost is around R135k including professional installation and all the required electrical protection and COC. This is a full hybrid system that provides for self-generation (electricity savings) and battery back-up.
- Or a Sunsynk 8kW Hybrid Inverter, 10.8kWh li-Ion battery & 4.5kW solar array. Full hybrid system for self-generation, electricity savings and battery back-up. From R200k.
Option 3:
- Install a 5kW Sunsynk hybrid inverter, 10.8kWh li-ion battery and 5.4kW solar array. Starting cost is R197k including professional installation and all the required electrical protection and COC.
- Sunsynk 8kW Hybrid Inverter, 14.4kWh li-Ion battery & 8.1kW solar array. Full hybrid system for self-generation, electricity savings and battery back-up. From R280k.
The right size inverter, battery and panels is determined by doing an energy audit and monitoring for around 7-10 days to determine your real energy usage as well as peak loads (the most energy you draw at any one time). Don’t accept a quote or system design without doing the proper groundwork.
With the advances in solar technology and pricing, you can hedge your electricity costs for the next 20-25 years and secure your supply at less than 50% of current prices that Eskom can supply it, by making savvy investment decisions today.
Avoid at all costs the cheap, quick fixes sold by fly-by-nights who promise you the world with a R10k inverter – if it were that easy and capable of taking you off the grid, everyone would have done it long ago. There are many unqualified fly-by-nights who have popped up, with even more questionable tech offerings and sub-standard installation quality. You’re going to be installing your solar system on your single most valuable asset and its pivotal to your quality of life, productivity and safety – so be sure to invest in the best quality systems and qualified installers with solid warranties.
90% Off grid versus 100% off-grid?
First off, it’s important to understand the system design and temper expectations with going full off grid. A system that takes care of 80-90% of your electricity needs is the best option from a financial perspective – with a connection to the grid to recharge the batteries during cloudy/rainy weather.
The last 10% to get entirely off the grid can prove very costly. An entirely off-grid system would need to be sized at least three times larger than a grid-tied system that uses Eskom/council as a backup when there is extended inclement weather. While adding a generator can charge up batteries, this comes with the ongoing costs of fuel, system maintenance and emissions.
A 5kW hybrid inverter, 10.8kWh li-ion battery and 5.4kW solar array will take a home using around 30kWh per day to around 90% off the grid. A system that takes care of 80-90% of your electricity needs is the best option from a financial perspective – with a connection to the grid to recharge the batteries during cloudy/rainy weather.
What is an essential vs non-essential load?
Your essential load consists of the appliances and equipment that you want to be able to power up in an outage while non-essential is exactly that – items that are not necessary or vital during an outage. By splitting your loads, you are able to use your batteries for longer to power up the essential equipment. Secondly, you also reduce the capital outlay needed on a bigger PV system and battery capacity if you were to try and power up everything in your home/office.
By splitting your essential and non-essential loads at your distribution board, a 5kW inverter with 10.8kWh li-ion battery, 5kW solar panels and a solar geyser will take an average household currently using around 25-30kWh of power per day to around 90% off the grid.
| Essential loads | Non-essential loads (heavy loads) |
|---|---|
|
Lights |
Anything with an element – geyser / kettle / dishwasher
|
|
TV and routers |
Aircons |
|
Fridge/freezer |
Heavy machinery and pumps eg pool/borehole pump |
|
Laptops/Computers |
Ovens/Stove (electric) |
|
Electric Fence / Alarm |
Underfloor heating/electric heaters
|
How long will my battery last?
The amount and duration of battery back-up is dependent on two factors – the size of the battery bank and the size of the load drawing power from it – in other words how many appliances you have running at the same time, and the total wattage being drawn by these appliances. It’s one of the reasons why we split essential and non-essential loads, to extend the battery capacity.
For purposes of this exercise, we used one 3.6kWh li-ion battery which allows for an 80% depth of discharge. This means that once your battery is discharged to having 20% power left, it is automatically disconnected by the inverter to protect your battery’s lifespan. You can of course add additional li-ion batteries if you require more back-up.
Estimated battery running times based on a 3.6 kWh li-ion battery:
| Wattage | Back-up time | Wattage | Back-up time |
|---|---|---|---|
|
2000W |
1.4 hours
|
1000W |
2.9 hours |
|
800W |
3.6 hours |
600W
|
4.8 hours |
|
400W |
7.1 hours |
200W
|
14.3 hours
|
Lithium Ion versus lead acid batteries?
Li-ion batteries have a phenomenal life span – with 6000 cycles+ at an 80% DOD – that’s a lifespan of 16 years (based on one cycle per day)! You can also expand your li-ion battery bank at a later stage and add more batteries within a certain time frame which you cannot do with outdated and cheaper lead-acid battery technology, which also only allows for a 50% depth of discharge (DOD). Essentially this means you can only use half of your lead-acid battery’s capacity, and the lifespan is 2-3 years at absolute best. With current load shedding at stage 4-6, you’ll be lucky to see a 12-month lifespan out of lead acid batteries.
Home energy storage systems using lithium-ion batteries have overtaken the market for good reason, and provide exceptional performance and lifespan compared with outdated lead acid batteries. Here’s a rundown on the two technologies:
- Li-ion batteries do not contain hazardous materials where lead-acid batteries contain lead which is toxic to the environment. Both battery types are recyclable.
- Lithium-ion batteries require less energy to keep them charged than lead acid batteries. Lead acid batteries also self-discharge at a higher rate than Lithium-ion.
- While the initial capital cost for lead-acid batteries is lower than li-ion batteries, which tends to make them more attractive for homeowners, the downside if that the cycle life of a lead-acid battery is much lower than that of lithium ion.
- Lithium-ion batteries offer at least 6 000 cycles and more and will last around 16 years (at one cycle per day) and typically discharge to 20% which means you have at least 80% usable power in your battery.
- Most lead batteries will typically cycle between 1,000 and 2000 cycles and last about 3 years, with a maximum depth of discharge of 50% – essentially meaning that only half of the battery capacity is useable. Over the lifetime of a solar array, a homeowner will have to replace lead-acid batteries numerous times, which makes the total cost of ownership uncompetitive with li-ion.
- Discharging lead acid batteries too deeply significantly reduces their life expectancy so a bigger capacity battery is required than the actual useable energy it can provide. Lead acid batteries therefore require a lot more space than li-ion batteries do. Lead acid batteries may produce hydrogen gas so need a well-ventilated situation.
- Lithium-ion batteries are lighter, far more compact (easier to accommodate) and generally aesthetically more acceptable than lead acid batteries.
The new cost of a Lithium-ion battery system keeps coming down and has already reached a point where cost over time is much less than the rate you can buy power from Eskom or your council. Longer cycle life, cost per kW and no maintenance costs makes li-ion batteries a far better option to outdated lead acid technology.
Track record and technical expertise matters!
Given the strategic importance of the decision you are making with regards to your electricity cost, supply and safety, as well as the quantum of your financial investment and expected ROI, work with a credible, qualified and accredited renewable energy partner that will be around for back-up, support and ongoing consultation over the lifespan of your system – that’s a good 20-25 years.
Download our handy checklist of the important considerations that One Energy suggests you look at when choosing a solar installer. Always go with reputable, quality and proven products installed by reputable companies with a national footprint and backing, and do check and verify their credentials. Done right the first time, going the route to grid-independence and solar generation is likely to be one of the very best decisions you can make in terms of investment in your safety, security and productivity.
