See what it takes to cut your electricity bill at your place.

• Panels are Aiko throughout: the 545 W dual-glass module on homes at about 2.2 m² each, and the Comet 665 W on commercial and agricultural jobs at about 2.7 m². Modules are priced per watt — R3.75/W on the 545 and R3.1875/W on the Comet — plus mounting per panel. Roof area assumes a clear, well-oriented pitch with room to work around the array. Mounting runs at R650 a panel, the Lumax blended rate covering rails, brackets and the fixings themselves on any pitched roof — tile roof hooks included, so a tile roof adds nothing to the mounting. What does add is structure over and above it: a ballasted flat roof R121 a panel for tilt frames and wind deflectors, and a ground mount R393 for footings. Tile, flat and ground all still carry the longer labour that goes with them.
• Inverters are sized to a 1.25 DC-to-AC ratio and snapped to the sizes each brand actually stocks, allowing a single unit to sit up to 10% under that target rather than racking two smaller ones. SigenStor runs to 12 kW single phase and 30 kW three phase, and its batteries stack 6 or 9 kWh modules, six to a unit; Sungrow batteries are priced as whole towers in 5 kWh steps to 40 kWh. On the commercial side a SigenStack takes 50, 110 or 125 kW inverters and 12 kWh blocks.
• A battery can only push so much power at once, so it has to be big enough to carry the inverter's full output. Both the Sigenergy and Sungrow batteries are 0.5C rated, meaning continuous output is half the installed capacity — so the rule is at least 2 kWh of battery per kW of inverter. On many systems that, not the backup time, is what sets the battery size.
• Pricing is built exactly the way we build a quote, off the live item list as at 15 October 2026: inverter and battery at our current retail rates, plus the energy gateway, panels and mounting, PV isolation, a sized AC combiner box and installation labour, then consumables, then VAT. Every rate is the sale price of the actual stock item we invoice — Aiko 545 W at R2,043.75, mounting at R650 a panel, a PVI 1000 V isolation box, Solar/AC consumables at R5,000 and installation and ECOC at R6,500 a day. Hardware is priced on the same basis for every brand, so Sigenergy and Sungrow compare like for like. The method reproduces our own quotes to within a rand or two. The band is rounded to the nearest R5,000 and runs from a straightforward job to a demanding one.
• Every SigenStor carries a Sigen Energy Gateway — the part that does the changeover and holds the backed-up circuits up when the grid drops. A single inverter takes the Home gateway (R6,962.50 single phase, R8,212.50 three phase); two take the HomeMax built for the pair (R15,387.50 and R21,987.50). On Sungrow that function sits in the SBH accessory box already in the price. On the C&I platforms a gateway only appears where the plant is large enough to need one: past three inverters a SigenStack takes a gateway to bring grid and generator in together. The inverter size sets the smallest that will do — the 300 kW unit behind 50 kW inverters, the 600 kW unit behind 110 kW — and the plant's own output then picks the rung above that: 300, 600, 1200, 1600 or 2400 kW, one bigger gateway rather than several small ones, and multiples of the 2400 only past that. Past six inverters a Sungrow Power Keeper takes the Energy Management Unit, one of them whatever the plant size, because it is a controller rather than switchgear. Below those counts neither needs one and neither is charged for one.
• Where a Sungrow Power Stack cabinet is used instead of the Power Keeper, the ATS is not in these figures. Whether one is needed at all, and what it has to switch, depends on what the site actually runs on — grid alone, grid and generator, or generator only — so it is priced on the design once the supplies are known, not estimated here.
• Labour runs two days on a single-phase system and three on three-phase, with more on large arrays. A supplementary Certificate of Compliance is included provided the property already holds a valid original CoC — if it doesn't, a full CoC is quoted separately.
• Output follows Aiko's warranted curve — 1% in the first year, then 0.35% a year — rather than the 0.5% a year a conventional module loses. Both panels carry a 30-year performance warranty. We allow R1,500 a year for servicing from year two, and one battery replacement in year 13 at 55% of today's battery price.
• Aiko's ABC cells run at −0.26%/°C against about −0.34%/°C for a conventional PERC or TOPCon module. On a KZN roof running roughly 20 °C above test conditions that is worth about 1.6% more energy, so the yield you enter — which is quoted for a conventional module — is lifted by that before anything else is worked out. Panel efficiency itself (24.6% on both the 545 and the Comet) buys roof area rather than energy, which is why the area figures above are as tight as they are.
• Self-consumption is worked out from your day and night split, not assumed: 85% of a day's generation lines up with daytime load, the surplus charges the battery at 90% round-trip efficiency, and only 90% of the battery's nominal capacity is usable. Anything the site can't absorb is exported or clipped, and the offset caps at 95% — nobody draws literally nothing from the grid.
• Everything on backup is not the same as off-grid, which is why they are separate options. Everything keeps the grid connection: the battery carries a full day's load through an outage, and the grid is still there behind it for the run of overcast winter days the array cannot cover. Off-grid cuts the connection, and three things change. The battery is sized for 1.5 days of the whole site rather than a night's load. The array is sized on a winter month — about 78% of the annual average yield in KZN — instead of the annual average, so it is materially bigger. And a generator becomes part of the design rather than a fallback: sized at roughly inverter kW ÷ 0.8 to get the kVA and snapped to a size you can buy, with automatic changeover and a comms link so the hybrid controls the charge rate rather than the generator running flat out. That generator is not in the price band, and neither is its fuel — the running cost shown for an off-grid site is diesel at R29/litre and about 0.30 litres per kWh, which is roughly R8.70/kWh and several times what the grid charges. That is the honest arithmetic of going off-grid: it is bought for independence, not for payback, and on a site that still has a working connection it almost never pays better than staying on it.
• The array is never sized bigger than the site can actually use. Add battery and more of the array earns its keep, which is why a bigger battery lifts the percentage covered as well as the backup time.
• R250 a month of your bill is treated as the fixed network and service charge. It stays whatever you install, so it's stripped out before we work back to kWh and added again to your new bill. Both lines on the chart are energy only, so it cancels out of the comparison.
• A commercial bill is taken apart before anything else happens. The kVA demand charge, the network access charge and the service and admin charge are all subtracted, and only what's left is energy — otherwise the array comes out far too big. The remaining spend is divided by a blended rate built from your three time-of-use rates and the share of usage in each period, which is what gives the kWh figure under the bill.
• Time of use decides what a kWh is worth. Generation is put where it actually lands on the clock — about 12% in the peak shoulders, the rest in the standard period — so solar is valued at roughly the standard rate, not the peak rate. Valuing solar at peak is a costly error. The effective rate the page works out is shown in the notes above the price.
• The battery does two jobs in the peak. It holds a reduction through a three-hour evening peak block, limited by whichever runs out first — its power (capacity × C-rate) or its energy. That cuts the measured demand, and the energy it delivers displaces peak-rate units. It charges from surplus solar where there is any and off-peak grid where there isn't, and the off-peak charging cost is netted off, round-trip losses included.
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• Tax is part of a commercial case, so it is in the numbers. A VAT-registered business claims the input VAT back, so the asset really costs the ex-VAT figure rather than the quoted price. Section 12B(1)(h) then writes that off against taxable income — the whole cost in year one for a generation plant under 1 MW, and 50/30/20 over three years above it. (The enhanced 125% allowance under Section 12BA lapsed on 28 February 2025 and is not used here.) The default rate is the 27% company rate; change it in the assumptions for a trust, a small business corporation or a sole proprietor, or clear the VAT box if the business is not registered. The flip side is applied too: electricity is a deductible expense, so on a commercial site both lines on the chart are after tax and the savings are worth what is left of them once tax is paid. That matters — because the allowance and the tax on the savings are struck at the same rate, Section 12B barely moves the payback year; what it does is hand the cash back in year one, which is where its real value sits. The VAT reclaim is what genuinely shortens the payback. Anyone showing you a commercial payback that credits 12B to the capex but leaves the savings untaxed is showing you a shorter number than the site will deliver. This is a sizing tool, not tax advice — your accountant signs it off.
• Above 15 kW the system goes on three phase, and above about 50 kW onto the commercial platform — Sigen C&I with SigenStack blocks, or the Sungrow SH125CX with Power Keeper packs. Commercial pricing here covers hardware, panels, mounting and labour on the same basis as a home; it does not cover roof structure, MV work, transformers, grid application or civils.
• Eskom's approved increases are 8.76% from April 2026 and 8.83% from April 2027 — 8.8% a year is the default here. Municipal rates on the North Coast differ; put your own rate in above.

This is a planning estimate, not a quote. It won't know about a shaded roof, a three-phase supply, an old distribution board or a borehole that starts on a hard load — which is exactly what a site visit is for.