Reading your electricity bill before you go solar

The Rand total at the bottom of your electricity bill is the number most people focus on, but it's not the one that actually matters for sizing a solar system. What matters is your average monthly usage in kWh — the actual amount of electricity you use, separate from what you're charged for it.

Why the Rand total is misleading

Two households using the same amount of electricity can end up with very different bills, because tariffs include fixed charges, block-rate pricing that increases the more you use, and municipal surcharges that vary from area to area. Your usage in kWh is found on an Eskom bill under your consumption figures, or on a prepaid municipal meter by checking your purchase history — that's the number that reflects what a system actually has to replace.

Time of use, if it applies to you

If you're on a time-of-use tariff, when you use power matters almost as much as how much you use — a chunk of usage happening in high-tariff hours changes the payback math on a system, even though it doesn't change the physical size of what you'd need.

Look at more than one month

Usage shifts across the year — geysers and heating push winter bills up in ways summer bills don't reflect. A system sized only for your best month leaves you short exactly when you need it most, so it's worth bringing a few months of bills, not just your most recent one.