Solar PV for office and EVs

Johannesburg, 15 Sep 2020
Read time 3min 40sec

AWPower engineers recently completed the conversion of its offices to sustainable living, including integrated facilities for charging battery powered electric vehicles (EVs). The objective was to design and install a solar PV system that would provide most of the energy requirements of the building by providing backup power during load-shedding, reducing costs and ensuring sufficient power to charge EVs during office hours. The results indicate an attractive model for future commercial buildings through increased and sustainable energy efficiency, a payback of around four years and proof that EVs could be charged primarily through solar generated power, thereby reducing their running cost to almost zero.

The solar PV system installed at AWPower’s Greenford Office Estate consists of 20kWp of roof-mounted solar PV modules, coupled with a combination of grid-tied (SolarEdge, Solis), hybrid (Victron, Goodwe) and battery tied inverters as UPS only (Mecer). Batteries used are a combination of popular AGM and Lithium Ion – 22kWh of battery capacity in total between the systems.

Please visit the infographic to view the installed system.

The savings in electricity following installation of the solar PV system amounts to approximately R4 500 per month at the current tariff. However, the savings in fuel through changing from internal combustion to an EV and charging the EV during office hours from this source, resulted in additional savings of approximately R3 000 per month.

Interesting observations worth noting on charging AWPower’s BMW i3 EV from solar generated power are:

  • When charging the EV batteries from a three-phase source, it is more economical to opt for a three-phase charger, rather than the regular single-phase chargers supplied with EVs. Typical after-market models can charge up to 16A x 230V = 3.68kW per phase, or 11kW combined (22kW units also available). At 11kW rate of charge, on a sunny day, the EV’s 33kWh battery can be fully charged from empty within three hours.
  • However, as most owners of solar PV equipped buildings know, every solar day is not a perfect sunny day, so the units in this example can be adjusted to reduce the load to 6A x 230V = 1.38kW/phase = 4.14kW combined.
  • Typical single-phase charger as shown in the picture can be switched from 8A (1.84kW) up to 32A (7.36kW). This is very practical when drawing from a residential single-phase installation where load-shifting must be applied to cope with loads like electric kettles, toasters, vacuum cleaner, geyser, etc.
  • A handy feature of grid-tied and hybrid inverters is the ability to supplement a lack of solar PV generation, by concurrently feeding from the grid as well. And using power from the grid does not make running an EV expensive. The average energy consumption for AWPower’s BMW i3 is 14kWh/100 km. At an electricity cost of 240c/kWh this equates to R33.60 per 100km. A similar sized internal combustion petrol car will consume approximately 8l/100km, and at a price of R14/l for unleaded petrol this equates to R112 per 100km, which is about three times higher than using electricity from the grid.

It can be concluded from the above case study that, with a grid-tied system, pay-back periods of less than four years for commercial buildings are within reach, especially if an annual increase of around 15% in the tariff are looming through Eskom’s claw-back initiatives. The additional tax incentives and attractive finance options outlined in a previous article makes opting for solar PV for commercial buildings a logical decision. When being financed, the monthly instalment should be covered by the savings.

And by adding an EV to this equation makes good economic sense, something that will certainly unfold over the next few years. See also what Bill Gates has to say about EV’s by visiting

Editorial contacts
AWPower Henri Hattingh (082) 371 3127
Login with