To understand the financial impact of smart automation (local electrical contractors, Straton Electrical, offer industrial scale automation as well as commercial and private automation) in the Nelson Mandela Bay (NMBM) area, we first have to look at the Inclining Block Tariff (IBT) structure for the 2025/26 financial year.
Under this system, the municipality charges a higher rate as your total monthly consumption increases. The “Penalty” or “Top” block is triggered the moment you exceed 500 units (kWh) in a single month.
The 2025/26 Domestic Tariff Breakdown (Non-ATTP)
Rates include 15% VAT.
| Consumption Block | Range | Price per kWh |
| Block 1 | 0 – 250 kWh | R3.48 |
| Block 2 | 251 – 500 kWh | R4.13 |
| Block 3 (High Block) | >501 kWh | R4.57 |
The “Shift” Calculation: Saving 100 kWh
If a household typically uses 600 units per month, the last 100 units are billed at the highest possible rate. By using automation to “shift” or reduce that load (staying at or below 500 units), the savings are substantial.
Monthly Savings (Direct Avoidance)
Cost of 100 units in Block 3: 100 kWh × R4.57 = R457.32
Total Monthly Saving: R457.32
Annual Savings
R457.32 × 12 months = R5,487.84
Note: This is nearly the cost of a mid-range solar inverter or a complete suite of smart relays for a standard home.
The “Efficiency” Saving
If you aren’t removing the load but simply managing it more efficiently (e.g., using a smart controller to ensure the geyser only runs when the household is actually using water, or load-shedding heavy appliances to avoid hitting that 501 kWh threshold), you are effectively keeping your “marginal cost” lower.
The difference between a unit in Block 1 and Block 3 is R1.09. For every unit you “save” from the top block and effectively move into your lower-tier budget through better efficiency:
Relative Saving: ~24% per unit.
How Smart Automation Achieves This
To stay under the 501 kWh threshold in a multi-appliance home (especially one with multiple geysers or fridges), Shelly automation installed by Straton Electrical acts as an “Energy Traffic Controller”:
- Geyser Load Management: Geysers typically account for 40% of a domestic bill. Automating them to run in short, high-efficiency bursts or during off-peak thermal periods can prevent “energy creep” into Block 3.
- Real-Time Threshold Alerts: Smart meters can trigger a notification or automatically shut down non-essential loads (like pool pumps or underfloor heating) the moment the monthly tally approaches 500 units.
- Appliance Interlocking: Preventing high-draw appliances (e.g., the oven and the tumble dryer) from running simultaneously doesn’t change the total units, but it reduces the strain on the system and helps in monitoring exactly where the “block-breaking” energy is going.
To stay below the 501 kWh threshold in Gqeberha, you are effectively playing a game of “load management.” In the Nelson Mandela Bay Municipality (NMBM), crossing into Block 3 (501+ kWh) significantly increases your cost per unit, making automation your best tool for a high ROI.
Geyser Automation: The “Heat and Hold” Strategy
A geyser typically accounts for 30–40% of a South African household’s energy bill. The goal is to heat the water just before peak demand and rely on the tank’s insulation to maintain temperature.
| Cycle | Time Window | Rationale |
| Morning Boost | 03:30 – 05:30 | Heats water before the 06:00 morning peak and before the first showers. |
| Afternoon Boost | 14:30 – 16:30 | Reheats the water before the 17:00 evening peak and dinner prep. |
| Weekend Flex | 10:00 – 14:00 | If you have solar, this is your “solar soak” window to use excess generation. |
Logic Rule: Use a Shelly Plus 1PM or Pro 1PM. Set a “Schedule” but add a “Local Action” or “Scene” that turns the geyser off immediately if the total house load (measured by your Shelly Pro 3EM) exceeds a certain limit (e.g., 5kW) to prevent “peaking” your demand.
Fridge Automation: Efficiency over Power-Cycling
Unlike a geyser, a fridge should not be aggressively power-cycled. Frequent “hard” restarts can damage the compressor and compromise food safety. Instead, focus on Thermal Management:
Pre-Cooling Logic: If you have a variable-rate tariff (like Homeflex), you can drop the fridge temperature by 1–2°C during off-peak hours (night) and let it “drift” slightly higher during the 17:00–20:00 peak.
The “Thermal Mass” Trick: Keep the fridge and freezer as full as possible. Use water bottles to fill empty spaces; they act as “cold batteries” that hold their temperature when the compressor is off.
Monitoring Alert: Use a Shelly Plus 1PM to monitor the “Duty Cycle.” If the compressor runs for more than 40 minutes an hour, it usually indicates a worn door seal or a dusty condenser coil—fixing this can save 5–10% on that specific appliance.
Staying Under 501 kWh: The “Monthly Run-Rate” Script
You can leverage Shelly Gen3/Gen4 scripting to manage your monthly budget dynamically.
Instead of a static schedule, you can implement a “Threshold Alert” script on your Pro 3EM:
Day 15 Check: If total consumption is >250 kWh, the script sends a notification to “Go Lean” for the rest of the month.
The “Safety Cut”: If consumption hits 480 kWh, the script can automatically disable non-essential loads (like guest geysers or pool pumps) to ensure you don’t tip into the Block 3 pricing.
Pro-Tip: In Gqeberha’s winter (June–August), your geyser will lose heat faster. Consider a “Geyser Blanket” combined with your Shelly automation; the blanket can reduce standing heat loss by up to 20%, allowing you to shorten your “On” windows by 15–20 minutes.
