Why we start with money instead of quantities
If you have R500 available, you may want to know how much electricity it buys or how far it will take you in petrol. You can also explore what saving R500 every month might add up to. The calculations answer different questions, so check the time period and assumptions before comparing them.
1. Work out what a once-off purchase buys
Suppose you use an illustrative electricity energy rate of R3 per kWh. R500 divided by three gives 166.7 kWh before any fixed fees or stepped tariffs. If you normally use 10 kWh per day, that is about 16.7 days of consumption; 20 kWh per day cuts that estimate in half. The same budget lasts longer when daily usage is lower.
For petrol, assume a hypothetical pump price of R25 per litre and a car averaging 7 L/100 km. R500 buys 20 litres, enough for an estimated 286 km. Traffic, vehicle condition, load and reserve requirements mean the real journey could be shorter. Both estimates depend on your actual usage and costs.
2. Compare a regular monthly payment
Saving R500 once and saving R500 each month are completely different commitments. Over five years, R500 monthly adds up to R30,000 of your own contributions, even if your savings earn nothing. Growth would depend on the return earned. A home loan calculation also uses a monthly amount, but estimates how much you could borrow. It cannot confirm lender approval or whether you can afford rates, levies and maintenance as well.
3. Check what the estimate leaves out
Every quick answer has exclusions. For energy: fixed charges, block tariffs and the actual provider. For driving: varying consumption, road conditions and pump price. For savings: inflation, fees, tax and uncertain returns. For borrowing: lending approval and recurring property costs. Read the exclusions alongside the result before using it to make a decision.
How to turn the result into a decision
Choose one assumption you can verify today. Read an energy bill to find the charge structure; use actual fuel receipts and distance travelled to establish car consumption; check the interest and term on a written lending quotation; or use the exact savings amount you can commit without borrowing. Run the calculation again with that input. Compare the new result with the example to see how much that input affects it.
We built the Money Mirror around this idea. It shows what one rand amount could mean for electricity, petrol, savings and a home loan. The labels distinguish once-off spending from monthly payments; the results do not rank one use of money above another.
Try the numbers yourself: Start with your rand amount or see how we calculate. These examples use assumed rates. Check the prices and terms that apply to you.