How the load-shedding cost calculator works
Last updated 10 November 2026
Outages cost more than the inconvenience: lost work, fuel for a generator, food that spoils. Adding them up is the first step in judging whether backup power is worth it.
How it works
- Monthly cost = lost work hours times what an hour is worth + generator fuel + food loss + other costs.
- Generator fuel = outage hours times the share on a generator times litres per hour times the fuel price.
- A system saves the share of those costs it removes, less its running cost. Payback is when savings reach the system cost.
Worked example
With the starting figures:
- Outages cost about R 2 400 a month with the starting figures.
- A system that removes the share entered would save R 1 920 a month.
- Simple payback is about 2.5 years.
How to read your result
The headline is what outages cost you in a typical month. With the starting figures that is R 2 400 a month, or R 28 800 a year. The rows split it into lost work, generator fuel, food and other costs, so you can see which part is largest.
The second half of the result looks at a backup system. With the starting figures it would save R 1 920 a month. The last row, saved minus cost over your chosen period, shows whether the savings overtake the price of the system.
A closer look at the value of an hour
The lost-work line is the hours of work lost multiplied by what an hour of your work is worth. That only counts if the work is really lost. If you can catch up later, or you can work on battery power anyway, the true loss is smaller.
For a salaried person, the hourly value is a way to put a number on lost time. For someone who is paid per job or per hour, the loss is more direct. Use the figure that matches how you earn.
Costs that are easy to miss
Beyond the obvious ones, these also add up:
- Food that spoils when the fridge or freezer is off.
- Candles, gas, data and power banks, which go in the Other costs box.
- Generator fuel, which depends on the hours it runs and how many litres it uses an hour.
- Running and upkeep costs of the backup system itself.
What this does not cover
The tool counts the costs of outages and the share a backup system removes. It does not count other benefits, such as a lower electricity bill. For that, use the solar payback calculator.
Savings are not discounted, and costs rise each year with an inflation assumption. Outage schedules also change, so the hours you enter today may not hold in future. Your area’s schedule or your own records are the best source for the outage hours.
Things to watch
- The value of an hour of your work only counts if the work really is lost.
- Schedules and outage hours change.
See also the solar payback calculator. Read the full disclaimer.
Like every tool on MoneyMzansi, this one runs in your browser. Nothing you enter is sent or stored, so download your data if you want to keep it.