AWPower Bulletin: November 2016
Following the release of “Living with Solar – Part 1”, AWPower received many enquiries about the cost of the various systems tested at our experimental site in Cape Town. In this edition, we elaborate on the costs of the most common type of PV systems including the factors that may have an influence on the costs, savings and payback period.
Cost drivers
The cost of solar PV modules has dropped by approximately 40% during the past 3 quarters in the international markets, making solar PV systems more affordable for small scale residential & commercial users. Although ESKOM assures us of no load shedding in the foreseeable future, the infrastructure supporting the distribution of electricity has become a risk as a result of little or no maintenance of transformers & cabling by municipalities, including theft of cables. Hence, when assessing the viability and cost of a solar PV system, energy security should also be considered.
In the examples below, we have assumed typical monthly electricity bills of R1,000 for Multi-Functional Inverter installations and R2,000 for Off-Grid Inverter installations. For Grid-tied Solar Inverter installations, electricity bills of R2,000 for the single phase and R10,000 for the medium sized three-phase commercial installations were used. For larger estates using the Bi-directional Hybrid Inverter, R2,500 is used for single phase and R4,500 for the three phase installations.
Please refer to the PV solutions section of the AWPower website for more detail.
MULTI-FUNCTION INVERTER
Transformer-less Multi-Function inverters provide for a low-cost entry to a solar PV solution, and are therefore more suitable for supporting the essential circuit of the household with uninterrupted power. The typical sizes range from 1kW to 4kW.
Application: Office & small house, essential loads.
* Assumed monthly Bill without solar – R1,000 & Tariff – 187.50 c/kWh
Ex = Expanded option
| Ref | System Info | Electricity Savings | % Generation from Solar |
Price (Excl. VAT) |
Payback * |
| M3 | 5kVA Multi-Function Inverter (4kW) with 6x260Wp (1.56kWp), 4x102Ah (2.45kWh) |
R 385 p/m | 39 % | R 58,600 | 8.7 years |
| M3 Ex | 5kVA Multi-Function Inverter (4kW) with 12x260Wp (3.12kWp), 4x102Ah (2.45kWh) |
R 770 p/m | 77 % | R 83,400 | 6.8 years |
OFF-GRID INVERTER *
Transformer-based off-grid inverters, such as the 6kW MLT Oasis inverter, are more efficient, reliable and suitable for heavy-duty applications where battery backup is required. These inverters will connect to the grid when running out of PV and battery power. Such systems are suitable for powering the full household or office/workshop, including geysers. Typical battery technologies are deep-cycle lead-acid or Lithium-Ion battery banks, which are managed by the self-consumption feature of the inverter
Application: Medium residential/office, off-grid farmhouse, only single-phase or 1 x inverter/phase.
* Assumed monthly Bill without solar – R2,000 & Tariff – 187.50 c/kWh
Ex = Expanded option
| Ref | System Info | Electricity Savings | % Generation from Solar |
Price (Excl. VAT) |
Payback * |
| O3 | 6kW MLT Oasis with 12x260Wp (3.12kWp), 8x225Ah (5.4kWh) | R 770 p/m | 39 % | R 137,800 | 9.3 years |
| O3 Ex | 6kW MLT Oasis with 18x260Wp (4.68kWp), 8x225Ah (5.4kWh) | R 1,155 p/m | 58 % | R 160,500 | 7.8 years |
| O3 Ex Ex | 6kW MLT Oasis with 24x260Wp (6.24kWp), 8x225Ah (5.4kWh) | R 1,540 p/m | 77% | R 200,200 | 7.3 years |
* On promotion during December 2016
BI-DIRECTION HYBRID INVERTER
The Bi-direction Hybrid inverter is suitable for a variety of applications such as off-grid farms, large estates and factories requiring clean incoming, voltage-regulated power. The MLT Powerstar is a robust & reliable Bi-direction Hybrid inverter with functionality to monitor all possible sources, simultaneously supplementing PV with the grid as well as control exporting power.
Application: Large residential/estates, off-grid farmhouse, factories, single & 3-phase.
* Assumed monthly Bill without solar – R2,500 & Tariff – 187.50 c/kWh
Ex = Expanded option
| Ref | System Info | Electricity Savings | % Generation from Solar |
Price (Excl. VAT) |
Payback * |
| B1 | 12kW Single-phase MLT Powerstar with 14x260Wp (3.64kWp), 16x225Ah (10.8kWh) | R 898 p/m | 36 % | R 243,900 | 13.1 years |
| B1 Ex | 12kW Single-phase MLT Powerstar with 24x260Wp (6.24kWp), 16x225Ah (10.8kWh) | R 1,540 p/m | 62 % | R 301,700 | 9.6 years |
* Assumed monthly Bill without solar – R4,500 & Tariff – 187.50 c/kWh
Ex = Expanded option
| Ref | System Info | Electricity Savings | % Generation from Solar |
Price (Excl. VAT) |
Payback * |
| B3 | 24kW 3-phase MLT Powerstar with 30x260Wp (7.80kWp), 24x225Ah (16.2kWh) | R 1,926 p/m | 43 % | R 437,700 | 11.7 years |
| B3 Ex | 24kW 3-phase MLT Powerstar with 64x260Wp (16.64kWp), 24x225Ah (16.2kWh) | R 4,109 p/m | 91 % | R 607,100 | 8.0 years |
GRID-TIED SOLAR INVERTER
A Solar Inverter that is directly grid-tied could supplement any power drawn from the grid by the load. The high-quality SMA Sunny range from Germany that comes with reverse power blocking devices installed (export limiting), the inverter can only produce what is being asked of it, while with exporting functionality, the inverter will produce as much as possible and export any excess power not utilized. However, when the grid is down, the system will be down too.
Application: Commercial & Industrial, single & 3-phase.
* Assumed monthly Bill without solar – R2,000 & Tariff – 228.77 c/kWh
| Ref | System Info | Electricity Savings | % Generation from Solar |
Price (Excl. VAT) |
Payback * |
| S1 | 3kW Single-phase Solar Inverter with 14x260Wp (3.64kWp) – no batteries | R 1,096 p/m | 55 % | R 97,700 | 5.2 years |
* Assumed monthly Bill without solar – R10,000 & Tariff – 129.25 c/kWh
Ex = Expanded option
| Ref | System Info | Electricity Savings | % Generation from Solar |
Price (Excl. VAT) |
Payback * |
| S3 | 20kW 3-phase Solar Inverter with 66 x260Wp (17.2kWp) – no batteries | R 2,921 p/m | 29 % | R 341,500 | 6.2 years |
| S3 Ex | 20kW 3-phase Solar Inverter with 84 x260Wp (21.8kWp) – no batteries | R 3,717 p/m | 37 % | R 411,000 | 6.0 years |
| S3 Ex Ex | 40kW 3-phase Solar Inverter with 168 x260Wp (43kWp) – no batteries | R 7,436 p/m | 74 % | R 807,900 | 5.9 years |