A slab system is designed so the first portion of usage can be charged at one rate while later portions can be charged at a higher rate. That means your full bill is not always one simple rate multiplied by total units. Instead, the bill is built in layers.
Why slabs matter
Slabs affect both your total bill and your average unit cost. A household that uses 60 units and a household that uses 120 units are not just paying for twice the electricity. The second household may be paying higher rates on the higher portion of that use, plus a different fixed charge structure depending on the tariff table.
A simple way to think about slabs
Imagine usage is poured into separate buckets. The first bucket fills at one rate. The next bucket fills at another rate. If your monthly usage crosses into more buckets, your total cost climbs faster than expected. That is the easiest mental model for slab pricing.
Worked example
If one home uses 55 units and another uses 95 units, the first home may remain within lower-priced blocks. The second home uses those same lower blocks first, but the remaining units spill into higher-priced blocks. That is why the per-unit average cost for the second home ends up higher.
How to use this information
- Track whether your household regularly crosses important usage thresholds
- Shift avoidable usage if you are close to a higher slab
- Use a calculator before buying high-consumption appliances
- Compare your average monthly usage over several months instead of one month only
FAQ
- Does every unit cost the same
- No. Under slab pricing, earlier units and later units can be priced differently.
- Does a small increase in usage always mean a small increase in the bill
- Not always. Crossing into a higher block can make the increase larger than expected.
- Can solar reduce slab pressure
- Yes. Lower net imported energy can help some users avoid higher-cost ranges.
Use the estimator to see how usage changes affect the bill instead of guessing.
Estimate Your Bill