Like all investments, hybrid solar has to be continually optimized.

Most people with a successful investment portfolio attribute that the success to buying correctly at the right time or selling at the right time or holding for the long-term. These decisions are made usually with the assistance of a broker who employs rafts of analytics to give the right advice.

Installing a solar solution in your home or business is no different and like any financial instrument, there are less expensive, more risky options that may not deliver the performance you expect. It is important to do your research, but this is easier said than done. The PV solar industry has a proliferation of acronyms and terminology which few people understand or for that matter, care about. kWh, kWp, kW, MPPT, SoC, net metering, Peak Shaving etc.

In South Africa the demand for hybrid solar systems (those that include batteries) has been driven mainly by the need to mitigate loadshedding and other power outages. As I write this, we are now into 100 days of zero loadshedding albeit that municipal infrastructure is now showing some severe cracks resulting in unscheduled outages.

However, the absence of loadshedding has been achieved by a concerted effort and no doubt a fortune of money spent on maintenance catch-up and a hurry-up on bringing Kusile and Medupi power stations online. Unfortunately, this means we can expect annual tariff increases in the teens, maybe even twenties of percent in the coming years. Add to this the unbundling of generation, transmission and distribution into standalone entities responsible for their own bottom-line and inevitably the end product to the consumer will be more expensive.

Contrary to this, the cost of solar equipment has come down substantially over time which is congruent with most maturing technologies as defined by Moore’s law in IT technology. In the PV solar context, we have Swansons Law which proposes that the price of solar photovoltaic modules tends to drop 20 percent for every doubling of cumulative shipped volume.

The preceding chart shows the price reduction for the year of 2023 from approximately $0,23 down to $0,13 per Watt peak. That’s a staggering 43% less in a single year. There is however context to this as there have been periods of oversupply during 2023 forcing manufacturers to sharpen the pencil.

The rough cost of a kWh for solar deployed in South Africa is R1,20 per kWh dependent on variables such as irradiation in your area, size of the system, cost of installation but as an average this would apply to most residential and small commercial systems. The average tariff for power sourced from Joburg City Power is R3,20 per kWh including VAT. Using the 900kWh per month average suburban household usage as a benchmark, utility provided power will cost you R2,880 per month excluding fixed costs.

Annual Cumulative Savings over 20 years assuming 15% tariff increase p.a.

By contrast, if you were to provide 600kWh/ month of your own solar power, it would theoretically cost you R720 for solar plus the additional 300kWh for grid at the lower block tariff of R2,71 resulting in R813 including VAT. Thus the total bill would be R1533 excluding fixed costs. The objective here is to get to the lowest tariff block but to retain your grid connection for cloudy days and for your high-load items such as an oven or geyser.

Silenergy advocate for getting geysers off the grid as much as possible as they are usually a big contributor to your energy usage of 30% to 40%. We approach this by using the same type of solar panels as deployed on your roof as the Hybrid PV system but using a seperate hybrid geyser box which uses both solar and grid-power to provide hot water.

This system retains your existing geyser and allows you to control how much grid versus solar you use depending on weather conditions and hot water usage. Three or four solar panels are usually required for such systems and you can expect to pay sub-R2000 per 560W solar panel and roughly R6500 for the geyser box. These systems usually pay for themselves in 24 months or less.

Hybrid standalone geyser solution

The capital cost of a household hybrid system to provide the 600kWh as described above would require 6 x 570W panels, 5kW inverter and 5kWh battery plus installation would approximate to R100,000. ROC period would be around 3 years against annual electricity increases but that is including the battery and the “lifestyle” advantages it offers.

Assuming this is advantageous and you elect to invest in a Hybrid PV system for your home or business, there are some obvious caveats such as product quality, performance and warranty. A reputable installer is imperative, so check references and look at past projects.

The primary objective of this article is to highlight the value of ongoing maintenance, system monitoring and configuration.

Managing your Investment

There is a misconception that PV solar systems are install and forget items, however, there is some post installation things to consider. Cleaning of solar panels, particularly in the dry months can deliver as much as 15% more generation than dirty, occluded panels. We recommend once a quarter depending on the specific environment. Solar panels on a sea-front house will need a lot more regular cleaning for example.

A regular maintenance inspection is also advisable to ensure panel mounts remain secure, no damage is evident on the panels themselves, all cabling is as-installed with no damage caused by birds or rats and that the roof structure itself is sound. Additionally, the inverter and battery equipment should be checked for fuse integrity, cabling and any other anomalies or safety issues that may have arisen.

Most PV systems come with an app for the purposes of initial configuration and ongoing monitoring. The functionality of these systems varies from manufacturer to manufacturer and some are quite complex, especially for non-technical people. As a suggestion, before committing to a specific system, take a look at the app offered by that manufacturer and assess if it will be intuitive to you or not.

The app is important as this where you will get the following basic information:

·         The current electrical load of the promises

·         What the state-of-charge of the battery is in percentage

·         How many kW of grid energy is being used

·         How many kW of PV energy is being generated currently and for the day thus far

·         How many kW of battery energy is being used

·         How much money the system has saved you

Over and above this, there are many technical parameters that need to be configured by the installers and it is best that these settings are left to the experts.

There are however changes that you as the client, may want to manage such as the Battery Reserve Capacity. Full hybrid systems allow the blending of power from solar, battery and the grid, usually in that order, but you can choose the priority. Given that the battery has two functions and that is one, to provide power to the premises during power outages. Secondly, the battery can supplement the solar or grid when there is no grid outage.

This can be useful if you produce excess solar power during the day which can be stored in the battery for use later in the day or night. Another cost-saving mechanism of a hybrid system, however, one needs to be cautious with using too much battery and then an outage occurs and there is insufficient battery left to get you through.

It is thus ideal to reserve a percentage of battery for such an eventuality. The question is how much battery should you save, as loadshedding and outages are often not anticipated. That would be a specific percentage relevant to your typical usage overnight. An outage during the day is not so critical as most times, the solar will charge the batteries.

When there is scheduled loadshedding, you will then be able to amend your battery reserve in accordance with the Stage of loadshedding expected. Depending on the size of your battery and your typical usage you can set the percentage you want to reserve. Thus at Stage 2 you may be able to get through with 35% battery reserve, however at Stage 6 you might need 70% reserve. The beauty of this is that you can save significantly on electricity bills by using battery in the evening but obviously when Stage 6 hits you will want to change the reserve capacity.

Most Silenergy sites are setup to only permit battery charging from the solar unless the owner specifies a period to permit charging from the grid. For example if there are cloudy days and irradiation is inadequate to generate sufficient energy to fully charge the battery, it will require a period of grid charge set on the app.  

App Example

Summary

Hopefully this dispels the perception that solar is all about loadshedding, in fact solar alone ie. without the batteries, does not provide power to the premises when the grid is down. A hybrid battery/solar system does mitigate power outages, including loadshedding, but does a whole lot more to reduce monthly bills.

Ultimately, Hybrid Solar is about continuity of electricity availability, saving your money and your planet. Silenergy recommend that you protect and optimize this investment through regular maintenance and continuous monitoring. This will ensure longevity of your system and ensure safety as well as a good financial return.