How Much Does 100 Units of Electricity Cost in South Africa?
Understand electricity costs, calculate your own bill, and learn why prices vary across South Africa.
How Much Does 100 Units Cost?
100 units = 100 kilowatt-hours (kWh) of electricity.
The cost depends on your municipality's electricity tariff. There is no single national price—tariffs vary significantly across South Africa based on the supplier, your customer category, and the consumption block you fall into.
The Basic Calculation
100 units × your tariff rate (R/kWh) = estimated energy cost
Example: If your tariff is R3.50 per kWh, then 100 units would cost R350 for the electricity alone.
Note: Your actual bill includes fixed charges, service fees, and possibly tiered pricing or taxes. This calculation shows energy cost only.
Hypothetical Cost Examples
These are mathematical examples only—not current South African electricity tariffs. They show how cost changes with different tariff rates:
| Tariff Rate | 100 Units × Rate | Cost |
|---|---|---|
| R2.50/kWh | 100 × R2.50 | R250 |
| R3.00/kWh | 100 × R3.00 | R300 |
| R3.50/kWh | 100 × R3.50 | R350 |
| R4.00/kWh | 100 × R4.00 | R400 |
| R4.50/kWh | 100 × R4.50 | R450 |
| R5.00/kWh | 100 × R5.00 | R500 |
Your actual tariff will differ. Find your real tariff on your electricity bill or contact your municipality.
Understanding Electricity Terms
What Is an Electricity Unit?
One electricity unit is the same as one kilowatt-hour (kWh). It is the standard measurement of electrical energy used in South Africa and most of the world. On your bill, "units" and "kWh" refer to the same thing.
What Is a kWh?
A kilowatt-hour (kWh) is a unit of energy. One kWh is the energy used by a 1,000-watt appliance running for one hour. Your electricity bill measures consumption in kWh, which is the same as units.
What Is a Tariff?
A tariff is the rate your electricity supplier charges per unit (kWh). It is shown on your bill as R/kWh (rands per kilowatt-hour). Different municipalities and suppliers have different tariffs.
Why Do Tariffs Differ in South Africa?
Electricity tariffs vary because different municipalities and suppliers have different costs. Supply areas differ, infrastructure costs vary, and some municipalities have different pricing structures for residential, business, or agricultural customers. Your tariff also depends on which consumption block you fall into.
How Long Will 100 Units Last?
How long 100 units lasts depends entirely on your household's daily consumption. There is no universal answer—it varies from household to household based on appliances, family size, and usage habits.
Use This Formula
Days = 100 ÷ average daily kWh consumption
Example 1: Low Daily Consumption
If your household uses 3 kWh per day:
100 ÷ 3 = 33 days
100 units would last about 33 days.
Example 2: Moderate Daily Consumption
If your household uses 5 kWh per day:
100 ÷ 5 = 20 days
100 units would last about 20 days.
Example 3: High Daily Consumption
If your household uses 10 kWh per day:
100 ÷ 10 = 10 days
100 units would last about 10 days.
Find your daily consumption: Check your electricity bill. Divide the total units used by the number of days in the billing period. This gives you your average daily consumption. Then use the formula above.
How Much Electricity Do Appliances Use?
Calculate any appliance's electricity use with this formula:
(Wattage ÷ 1,000) × hours used = kWh
Or in simpler terms: Wattage in watts, divide by 1,000, then multiply by the number of hours the appliance runs.
Worked Example 1: Television
Appliance: 100W television
Usage: 4 hours per day for 30 days
Calculation:
(100 ÷ 1,000) × 4 hours × 30 days
= 0.1 kW × 4 × 30
= 12 kWh per month
Cost: 12 kWh × R3.50/kWh = R42 per month
Worked Example 2: Electric Kettle
Appliance: 2,000W kettle
Usage: 10 minutes (0.167 hours) per day for 30 days
Calculation:
(2,000 ÷ 1,000) × 0.167 hours × 30 days
= 2 kW × 0.167 × 30
= 10 kWh per month
Cost: 10 kWh × R3.50/kWh = R35 per month
Tip: You can find an appliance's wattage on its label, nameplate, or product manual. Some appliances (like microwave ovens) show wattage in the product specifications.
How to Find Your Electricity Tariff
To calculate your own electricity costs, you need to know your tariff rate (R/kWh). Here's how to find it:
Method 1: Check Your Electricity Bill
Look for a line showing "Rate" or "Tariff" or "Rate per unit" or "R/kWh". It may also be called "unit rate" or "energy rate". This is your tariff.
Different consumption blocks may have different rates, so check which block your consumption falls into.
Method 2: Contact Your Municipality or Supplier
Call your local municipality or electricity provider and ask for your tariff rate. Provide your customer account number.
Be specific about your customer category (residential, business, etc.) as tariffs differ.
Method 3: Visit Your Municipality's Website
Many municipalities publish their tariff schedules online. Search for your municipality's electricity tariffs or rates.
Tariffs usually change annually, typically in July.
Use Our Calculator
Once you know your tariff, use our electricity cost calculator to see exactly how much your appliances cost to run. Enter your wattage, hours of use, and tariff for personalised estimates.
Go to CalculatorFrequently Asked Questions
How much does 100 units of electricity cost?
It depends on your municipality's tariff. Multiply 100 by your tariff rate (R/kWh). For example, at R3.50/kWh, the energy cost is R350. However, your bill will also include fixed charges, service fees, and possibly tiered pricing or taxes. Check your bill to find your specific tariff.
Is 100 units the same as 100 kWh?
Yes. One unit of electricity equals one kilowatt-hour (kWh). South African electricity bills measure consumption in units, which is the same as kWh. The terms are interchangeable.
How do I calculate my electricity cost?
Use this formula:
Units used × your tariff (R/kWh) = estimated energy cost
Find your tariff on your electricity bill. Multiply the units you used by this rate. Remember to add any fixed charges shown on your bill for the total cost.
Why does 100 units cost different amounts in different areas?
Because different municipalities and electricity suppliers charge different tariffs. Tariffs depend on supply infrastructure, local demand, operational costs, and sometimes different customer categories (residential vs. business). There is no national electricity price in South Africa.
How long will 100 units last in my household?
It depends on your daily consumption. Use this formula:
Days = 100 ÷ your average daily kWh
For example, if you use 5 kWh per day, 100 units will last 20 days. Check your recent electricity bill, divide the total units by the number of days, and calculate from there.
Does prepaid electricity have additional charges beyond the per-unit cost?
Yes. Most prepaid electricity systems include standing charges or service fees in addition to the per-unit energy cost. The amount varies by municipality. Check your prepaid meter's receipt or contact your supplier to see your full tariff structure, including any fixed charges.
How do I calculate what an appliance costs to run?
Use this formula:
(Wattage ÷ 1,000) × hours used = kWh
Then multiply kWh by your tariff to find the cost. For example, a 100W television used 4 hours per day costs: (100 ÷ 1,000) × 4 × 30 = 12 kWh. At R3.50/kWh, that's R42 per month.
Important Disclaimer
Electricity tariffs, billing structures, and charges vary significantly across South Africa depending on your municipality, supplier, customer category, and consumption block. The tariff examples in this article (R2.50–R5.00/kWh) are mathematical illustrations only and not actual South African tariffs.
Your actual electricity bill includes not only the per-unit energy cost but also fixed service charges, network charges, applicable taxes, and potentially tiered pricing if you exceed certain consumption thresholds. Bills may also include municipality-specific levies or adjustments.
To know the exact cost of 100 units for your household, check your own electricity bill for your tariff rate and billing structure, or contact your municipality or electricity supplier. The information on this page is for educational purposes and general understanding only.