Peak Demand Shaving: The Hidden Cost on Your Eskom Bill — and How to Eliminate It

The Line Item Most Businesses Never Question

Ask most finance directors about their electricity bill and they'll point to consumption — kilowatt-hours used per month. But for commercial and industrial customers on Megaflex, Miniflex, or TOU tariffs, the real sting is elsewhere: the demand charge, measured in kilovolt-amperes (kVA).

Demand charges are fees based on the single highest 30-minute power draw in a billing period. Hit one spike — a Monday morning when every machine starts simultaneously — and you pay for that peak all month. According to industry data, demand charges can account for 30 to 70 percent of a commercial electricity bill.

What Is Peak Demand Shaving?

Peak demand shaving is the strategic reduction of your maximum power draw from the grid during the most expensive windows of the day. Rather than allowing motors, compressors, chillers, and lighting to all draw from Eskom at once, a BESS system detects when demand is approaching a threshold and instantly injects stored energy to bridge the gap.

The result: your grid meter never sees the spike. Your demand charge never triggers. Month after month, your bill drops — not because you're using less energy, but because you're using it more intelligently.

The Numbers Stack Up Fast

Consider a mid-sized manufacturing operation drawing a peak demand of 500 kVA. On Megaflex tariffs, shaving just 100 kVA off that peak can generate recurring annual savings running into six figures in rands — regardless of how much electricity is consumed. Multiply that across multiple sites or scale up the system, and the return on investment becomes compelling within three to five years.

The BESS acts as what engineers call an intelligent physical limiter. It monitors your load profile in real time, charges from solar or the grid during off-peak hours at low cost, and discharges precisely when needed to cap your demand footprint.

Combining Peak Shaving with Energy Arbitrage

The most effective BESS deployments don't just shave peaks. They combine peak shaving with energy arbitrage — charging the battery when Eskom's time-of-use tariff is at its lowest (typically overnight or at midday during solar generation) and discharging during evening peaks when tariffs are highest.

This dual strategy delivers savings on two fronts simultaneously: lower demand charges and lower consumption costs. For businesses on TOU tariffs, SolarHub engineers a system that maximises both benefits automatically, with no manual intervention required.

SolarHub Designs Your System for Maximum ROI

Every business has a unique load profile. SolarHub analyses your historical consumption data, identifies your demand spikes, and sizes a BESS solution specifically to flatten them. We include all SSEG registration, grid compliance, and full ongoing monitoring in our service — so you save from day one and never have to manage the system yourself.

➜  Find out how much your business is losing to peak demand charges. Book your free SolarHub energy audit.