Our New Office: Chapter 10 – targeting Net Zero

Our New Office: Chapter 10 – targeting Net Zero

Solid Green’s new office in Parkhurst runs completely off the grid. Here, Chilufya Lombe shares the reality of what it has taken to embark on the solar journey, and the benefits experienced.

The first rule of sustainability is to align with natural forces, or at least not try to defy them.

Paul Hawken

 We often use Paul Hawken’s quote to start or end our presentations to clients and project teams. By following this ethos, we believe we can create spaces that are more aligned with nature and can therefore achieve more than we think is possible.

While our goal was always to ensure that our office building adheres to the levels of sustainability we advocate, a bit of misfortune pushed us to really test the boundary of just how much we could align with nature. Our office construction project started just before the onset of the hard lockdown due to Covid in 2020. The site sat with a half-demolished building for over eight months and, in this time, the municipal meter and infrastructure were stolen.

This pushed us to install our solar system much earlier than anticipated and also drove the decision to stay completely off the grid. There is often some confusion between net-zero and off-grid: you can be net-zero without being off-grid. In our case, we are net-zero because we are off-grid. Our only source of power is the sun.

Our office can accommodate all 20 of our staff members. With remote work, the actual numbers vary from 5 to 15 in the space at any given time. Each staff member has a laptop and a screen, and our 4 modelling team members work off desktops with two screens each. Despite this, our installation is smaller than one that would usually be installed in a 4-person home.

Natural Hours of our building


Energy in our office is used primarily for the delivery of our services, namely to power equipment like computers. Not needing energy for lighting or comfort means our building is able to run only on power available from the sun.

 We are an ‘A’ whichever way you look at it.


Energy performance certificate (EPC) benchmarks have recently been updated. This is causing some concern in the industry as the new benchmarks, shown in red, are significantly lower than the old benchmarks, shown in blue. Even taking the new updates into account, our office still outperforms an ‘A’. This shows what can be achieved if energy for comfort and lighting is reduced significantly. Particularly for offices.

The journey is not without its challenges. Our backup is only a 5kWh battery. That is enough to power your geyser at home for only 2 hours. Our original installation was 6,450W solar panels – enough power to turn on the electric element in a geyser. We eventually added additional panels (12 x 180W, they were tiny) that had been taken from our old office. This almost doubled our capacity and improved our ability to continue working on low sun days.

A key problem was that, if the battery was very low, we needed more energy earlier in the morning. We faced the additional panels slightly east to remedy this, ensuring that we get more energy early in the day if the battery was empty from the day before.

The battery is large enough to keep the fridge and security system running overnight with no issues. We have controls that switch off all monitors, TVs, printers and lights at exactly 6-30pm every day. We have always advocated for our team to have a good work-life balance, so we expect the office to be empty by then. External security lighting is all solar lighting that has its own integrated battery.

Our biggest challenge comes if we have two consecutive days of no sun. Even with direct sunlight, our solar panels generate a small amount of power and, because we only need a small amount of energy, this can keep us going through the day with the help of the battery. No sun days, however, means our battery does not charge and so the second day of no sun requires some load management. Like Eskom, we have a few levels of load management (to prevent shedding):

  • Stage 1 – Turn off fridge, TV and non-essential kitchen appliances unless using them. Items like kettles and microwaves can be used for a very short space of time because they tend to be high power but low energy.
  • Stage 2 – All kitchen appliances are switched off and cannot be used.
  • Stage 3 – All kitchen appliances plus all screens are switched off and cannot be used, except for the modelling team.
  • Stage 4 – All kitchen appliances plus all screens are switched off and cannot be used, except for the modelling team. When battery gets to zero, go home.

In 18 months of occupation, we have had stage 4 only once. Even stage 1 is rare. We only need the sun to peek from behind the clouds for an hour or so to alleviate any issues.

Challenges and future plans

 Living with nature cannot always be perfect. Johannesburg is cold in winter and, while the passive design interventions employed in our office mean that we have not required cooling in summer, we do need a heating solution for cold winter mornings. Our challenge is that it needs to fit within our current energy budget and we do not want to increase the solar production or battery backup to accommodate heating. We believe we have found a solution that meets this requirement and hope to have it in place in time for next winter.

That will be a story for another day though…

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