Does a battery pay for itself on Eskom Megaflex time-of-use in 2026?

Answer first: Megaflex is the tariff where a commercial battery earns real money. Eskom prices the five weekday peak hours far above off-peak, and the spread is widest in June, July and August. A battery that charges from surplus midday solar or 123 c off-peak power and discharges into the peak turns that spread into a monthly saving. Size it to the peak kWh you actually buy, not to a brochure kWh number. Related: demand charges and solar · commercial BESS · commercial solar desk.

The 2026/27 Megaflex energy rates, in one table

Eskom raised its large-power urban tariffs — Megaflex, Miniflex, Nightsave Urban and WEPS — by 8.76% from 1 April 2026 (Eskom 2026/27 tariff increase page). The active-energy rates for the most common small-commercial connection, low voltage below 500 V and within 300 km of Johannesburg, are:

All figures excl. VAT, Megaflex non-local authority, <500 V, ≤300 km. Sources: Eskom Schedule of Standard Prices 2026/27; Augos tariff database, Megaflex non-local 2026/27 (accessed 27 Oct 2026). Medium-voltage sites (500 V to 66 kV) sit slightly lower: 720.19 c peak in winter, 298.89 c in summer, 120.03 c off-peak. On top of energy, Megaflex adds a legacy charge, affordability subsidy, ancillary service charge and kVA-based network and generation capacity charges. Those do not change with timing, so they drop out of the arbitrage maths — except the demand-linked network charge, covered below.

When peak actually happens

NERSA’s Retail Tariff Plan decision shortened the morning peak to two hours and stretched the evening peak to three, and lowered the peak-to-standard ratio from 1:8 to 1:6 (NERSA Reasons for Decision on the Eskom Retail Tariff Plan). For 2026/27 the weekday windows are:

• High-demand season (1 June – 31 August): peak 06:00–08:00 and 17:00–20:00; standard 08:00–17:00 and 20:00–22:00.
• Low-demand season (September – May): peak 07:00–09:00 and 18:00–21:00; standard 06:00–07:00, 09:00–18:00 and 21:00–22:00.
• Weekends: no peak. Saturday carries standard blocks; Sunday has a two-hour standard window in the evening (17:00–19:00 in winter, 18:00–20:00 in summer).

Every other hour is off-peak (GridPulse ZA time-of-use table). The headline for a business: five peak hours a weekday, about 1 250 peak hours a year, and the three evening hours are the expensive block that solar cannot reach without storage.

The arbitrage maths per delivered kWh

A battery never returns every kWh you put in. We use 90% round-trip efficiency as the working figure for battery plus inverter; replace it with the number on your own system’s datasheet. At 90%, a kWh bought off-peak costs 123.20 c ÷ 0.9 = 136.89 c per kWh delivered back out of the battery.

Now scale it. A site that discharges 100 kWh into the peak every weekday, with roughly 65 working weekdays in the winter season and roughly 185 in the summer season, earns about 100 × R6.02 × 65 ≈ R39 100 in winter and 100 × R1.70 × 185 ≈ R31 400 the rest of the year. That is about R70 500 a year excl. VAT per 100 kWh shifted daily. Double the shift, double the saving — as long as your peak load is big enough to absorb it.

Divide the installed price of the battery by that figure and you have a first-pass arbitrage payback. Add the solar and demand effects below and the payback shortens further.

Solar charging beats off-peak charging

Off-peak grid power at 123 c is cheap, but surplus midday solar on a zero-export site is free. Many commercial roofs already curtail at lunchtime because the business is on a zero-export setting or the municipality has not approved export. Every curtailed kWh stored and released at 18:00 avoids a peak kWh outright. In winter that is 739 c of avoided cost for a kWh that would otherwise have been thrown away.

Where a site does export under an approved generator tariff, value the stored solar kWh at the export credit you forgo, not at zero. On Eskom supply that is the Gen-offset credit printed on your schedule; in a metro it is the published SSEG credit. Either way the gap to a peak kWh stays wide. See zero-export solar and clipping and export limits.

The demand charge: where batteries earn a second income

Megaflex bills network demand on the chargeable demand — the highest average kVA demand recorded in the peak and standard periods of the month (Eskom Tariffs and Charges Booklet 2026/27). A kettle-and-compressor spike at 07:30 sets the charge for the whole month. A battery that clips that spike earns on two lines at once: the energy saving above, plus a lower kVA figure on the demand line. Ask your installer to model both from your actual half-hour meter data, not from a monthly total. Our demand-charge explainer walks through the kVA arithmetic, and NMD rules explain why the notified maximum demand stays on the bill even when the peak drops.

Sizing the battery to the peak you buy

1. Pull 12 months of half-hour data. Eskom large-power customers have interval metering; ask your account manager for the export.
2. Add up weekday peak kWh per day. That is the ceiling for arbitrage. A battery larger than the peak you buy only earns on the smaller summer spread or sits idle.
3. Size the inverter to the peak kW. Five peak hours a day means a 100 kWh shift needs about 20 kW of continuous discharge spread over the windows, more if the load is concentrated in the evening.
4. Check usable kWh, not nameplate. Work in usable capacity at the depth of discharge the warranty allows — usable kWh explained.
5. Price it in rand per usable kWh and per lifetime kWh. Divide the price by usable kWh, then by warrantied throughput. That second number is the true cost of every arbitrage cycle.

Cycle life is the hidden line in the business case

Arbitrage cycles a battery every weekday — about 250 full cycles a year. Ten years of that is 2 500 cycles before you count solar top-ups on weekends. Read the throughput warranty, not only the years. Solar MD, for example, publishes a 12-year or 84 MWh warranty on its SS4160 to at least 60% capacity, built and supported in South Africa (Solar MD; our breakdown) — the kind of throughput figure a daily-cycling commercial bank needs. Compare it with peers on the same basis: warrantied MWh divided into price gives you rand per cycled kWh, and that number must sit well below the R1.70 summer spread for year-round arbitrage to make sense.

For larger sites, 48 V DC modules stack into racks, while high-voltage commercial cabinets suit 100 kWh-plus projects. 48 V DC remains the oldest, most proven architecture for hybrid systems and is the right choice for small commercial loads up to a few tens of kWh — stacking hybrids.

Tax and finance shorten the payback

A business that owns a battery charged by its own solar PV system can include it in the PV system’s cost under section 12B, which allows 100% of the cost of a PV system up to 1 MW in the year it is first used. SARS’s guide is explicit that a battery qualifies only when it forms an integral part of a generating system; a battery that only stores grid power does not (SARS guide IT39 on renewable-energy allowances). Read our section 12B guide before you split the invoice.

On finance, prime has been 10.75% since 25 September 2026 (Absa financial indices); Standard Bank’s business solar finance is published as prime + 2.5% over 60 months (SolarGuide bank comparison (checked 21 Oct 2026)). Interest is a cost line in the arbitrage model, so run the numbers cash and financed side by side.

Where Megaflex sites waste their battery

• Discharging at the wrong hour. Many inverters ship with residential evening schedules. Program the windows to Eskom’s 2026/27 TOU table and change them on 1 June and 1 September.
• Charging from standard-time grid power. Standard at 172–185 c is above off-peak; charging at 10:00 from the grid instead of solar or overnight wastes 50–60 c per kWh.
• Ignoring weekends. No peak on Saturday or Sunday. Use the battery for solar self-consumption and keep it full for Monday 06:00 or 07:00.
• Treating backup as the business case. Backup reserve is a small slice of capacity, set on the inverter. The money is in the peak and demand lines.

Bottom line

On Megaflex, the battery pays for itself through the weekday peak. A delivered kWh is worth about R6 in winter and R1.70 in summer after losses, the demand line adds a second saving, and free midday solar makes the cheapest charging source of all. Size to your peak kWh, price on rand per lifetime kWh, claim section 12B where it applies, and program the TOU windows correctly. Get the wholesaler and installer quotes side by side through our quote checker.

Quick questions

What are the Megaflex peak hours in 2026/27?

Weekdays 06:00–08:00 and 17:00–20:00 in the high-demand season (1 June to 31 August), and 07:00–09:00 and 18:00–21:00 in the low-demand season (September to May). Weekends carry no peak hours.

How much is a Megaflex peak kWh in 2026/27?

For a low-voltage (<500 V) supply within 300 km of Johannesburg, 739.28 c/kWh excl. VAT in the high-demand season and 306.82 c/kWh in the low-demand season, against 123.20 c/kWh off-peak in both seasons.

Is battery arbitrage worth it outside winter?

It earns about R1.70 per delivered kWh from September to May, a third of the winter figure. The battery pays its way when it also stores midday solar that would otherwise be curtailed and trims the demand peak.

Should a Megaflex site charge from solar or the grid?

Solar first. Surplus midday solar on a zero-export site is worth nothing unless you store it, so charging from it costs you nothing beyond battery wear. Top up from off-peak grid only on days the sun falls short.