Building a Tesla Powerwall 3 for R100,000 cheaper

It is possible to configure an inverter-and-battery system with similar specifications as Tesla’s Powerwall 3 for less than half the price.

However, this system may not be capable of Tesla’s autonomous intelligent power balancing and charging capabilities without additional components and tinkering.

Tesla’s latest backup energy system was launched in South Africa this week.

It offers the same 13.5kWh of energy storage as its predecessor, but continuous output has been boosted from 5kW to 11kW.

In addition, the system no longer requires a separate inverter to connect with solar panels.

The Powerwall 3’s recommended retail price is R181,873, excluding installation.

That makes it over R40,000 more expensive than the Powerwall 2 and Gateway’s launch price in South Africa in late 2019.

That is despite the Powerwall 3 launching at $200 (R3,676) less than its predecessor in the US when it debuted in September 2023.

It is important to note that the rand is currently much weaker against the dollar than when the Powerwall 2 launched in December 2019. Back then a dollar cost around R14.50. Today, it is trading at R18.30.

However, other solar and backup product prices have plummeted in the past two years.

One MyBroadband analysis found that popular portable power stations were around 50% cheaper in November 2024 than in June 2023.

Another comparison found that the prices of fully integrated solar and backup systems from a popular installer had declined by 23% to 33%.

The Powerwall 2 was already far more expensive than a custom inverter-and-battery configuration.

MyBroadband devised an alternative system that can provide similar performance as the Powerwall 3 using components from some of the most affordable yet trusted brands.

To match the Powerwall 3’s continuous output, we chose the Deye 12kW single-phase inverter.

The Chinese company’s products are widely available and popular with prominent solar power installers due to their balance of price and reliability.

The 12kW model has a slightly higher output than the Powerwall 3 but its price tag of R35,000 to R40,000 put it well within our budget.

For storage, we opted for the Dyness Powerbrick with 14.3kWh of capacity. Multiple retailers were selling this model for between R30,000 and R40,000.

When used with its maximum rated depth-of-discharge, the Powerbrick has nearly exactly the same capacity as the Powerwall 3.

It also boasts similar recommended battery charge and discharge ratings, which determine how much of the battery’s power can be used continuously without damaging its long-term life.

Using the retailers we identified, the custom system would cost R76,780, over R105,000 less than the Powerwall 3.

The table below compares the specifications of the Powerwall 3 and our custom system with similar specifications.

Ah… there’s the rub

One of the key benefits of Tesla’s solution over the custom system is its software. Tesla is renowned for how it uses real-world data and telemetry to make its products smarter.

The Powerwall’s software is no exception, as it can intelligently manage electricity sources and charge the battery at just the right time to achieve the maximum potential savings in grid expenditure.

Key to this is the Gateway smart hub, which is connected directly to the home’s distribution board.

It is effectively the system’s brain for safe and efficient energy management.

The Gateway can automatically turn certain appliances like geysers or pool pumps on or off based on solar generation availability and battery levels at any given time.

While it is possible to fit smart switches to the circuit breakers for higher-demand appliances in a custom-built solution, it is far more complex to get them to operate autonomously.

Users typically have to put their energy-intensive appliances on timers that ensure they make the best possible use of solar power when available.

However, getting this right can sometimes be a shot in the dark during rainy seasons, when clouds can severely impact performance and may make it necessary to repeatedly switch an appliance like a geyser on or off for optimal solar usage.

The more tech-savvy homeowners can create a link between their inverter and smart switches with a Raspberry Pi computer using open-source software like Home Assistant.

However, such configurations are complex, which is why the Tesla Powerwall 3 certainly has a place in the market.

The other major benefit of the Powerwall 3 is that it boasts significant environmental protection, enabling installation outside.

There are no other backup energy storage systems for households in South Africa which feature an IP67 dust and water proof rating.

The Powerwall 3 can even continue running when submerged in up to 60 centimetres of water during a flood.

The system is also far more compact than a separate inverter and battery, great for households and businesses with limited space.