Solar Battery Calculator
Size your battery backup system for South African load shedding — select your essential loads, set backup hours, and compare lithium vs lead-acid economics
Battery Storage for South African Load Shedding How to size • Technology • Costs
How Battery Storage Differs from Solar Panels
A battery backup system stores electricity (from Eskom or solar panels) and releases it during load shedding. Unlike a solar ROI calculation — which focuses on generating electricity and reducing your grid bill — a battery system is primarily about energy resilience: keeping your essential loads running when Eskom cuts power.
You can have a battery system without solar panels (charged overnight from the Eskom grid at off-peak rates), or combine batteries with solar for maximum independence. This calculator focuses on the battery storage component.
Understanding Battery Capacity and DoD
Battery capacity is measured in kilowatt-hours (kWh). A 10 kWh lithium battery can theoretically power a 1 kW load for 10 hours. However, Depth of Discharge (DoD) limits how much energy you can use:
- Lithium (LiFePO4): Can be discharged to 80–90% safely. A 10 kWh battery provides 8–9 kWh usable energy. Lasts 4,000–6,000 cycles (10–15+ years).
- Lead-acid / AGM: Should not be discharged below 50% without damaging the cells. A 10 kWh battery provides 5 kWh usable. Lasts 500–1,000 cycles (2–4 years with daily cycling).
- Gel batteries: Similar to AGM but slightly better at partial-state-of-charge cycling. Still much shorter lifespan than lithium.
Load Shedding Stage Guide
During Stage 4 or higher, a single daily load shedding cycle can last 2.5–4 hours. For evening resilience (cooking, lighting, security), you need 4–6 hours of backup. For overnight resilience, plan for 8–12 hours.
Worked Example
Priya in Cape Town wants to run lights (150W), TV/decoder (150W), fridge (200W), router (30W), and security system (100W) during 4-hour evening load shedding slots — Stage 4 conditions.
Total load: 630W = 0.63 kW. Over 4 hours: 2.52 kWh raw energy needed. With 85% DoD on lithium: 2.52 ÷ 0.85 = 2.96 kWh battery capacity needed. A single 5 kWh LiFePO4 battery (e.g., Pylontech US5000) comfortably covers this.
System cost estimate: 1× 5kWh battery ~R22,500 + hybrid inverter ~R27,500 + installation ~R10,000 = ~R60,000 total. At Stage 4 load shedding of 20 hrs/week and R3.50/kWh, annual Eskom saving is approximately R5,460/year, giving a payback of about 11 years — primarily a resilience investment, not purely financial.
Frequently Asked Questions
How much does a home battery backup system cost in South Africa?
A typical South African home battery backup system costs R60,000–R120,000 fully installed. This includes a hybrid inverter (R15,000–R40,000), a 10 kWh lithium battery bank (R30,000–R60,000), and installation (R5,000–R15,000). Small systems for essential loads only (5 kWh) start from approximately R45,000. Prices have dropped significantly since 2022 due to increased import volumes and local competition.
Which battery brand is best for South African load shedding?
Popular and well-supported lithium battery brands in South Africa include Pylontech (widely available, 10-year warranty), Freedom Won (South African brand, excellent warranty and support), Hubble (SA brand, good value), and Sunsynk (integrated inverter-battery systems). For smaller budgets, Greenrich and Revov (reburbished cells) offer lower-cost options. Always choose batteries compatible with your inverter brand and SANS 10142 compliant.
Do I need a Certificate of Compliance for a battery installation?
Yes. Any electrical installation, including battery backup systems, must comply with SANS 10142 (Wiring of Premises) and requires a Certificate of Compliance (CoC) issued by a registered electrician. For lithium battery systems specifically, fire safety requirements apply — the installation location must meet ventilation and fire rating standards. The CoC is also required for home insurance validity and when selling your property.
Is a battery backup system or a generator better for load shedding?
Both have merits. A battery system is silent, requires no fuel, and powers sensitive electronics safely. A generator can power larger loads (air conditioning, electric stove) at lower upfront cost. Over 10 years, a petrol generator costs R5–R6 per kWh (fuel + maintenance), versus R1.50–R3 per kWh for a battery system. Battery wins on long-term economics and convenience; generator wins on raw power capacity and low upfront cost.
Can I add solar panels to my battery system later?
Yes, if you install a hybrid inverter (rather than a standard inverter/UPS). A hybrid inverter supports solar panel input (MPPT charge controller) and can be retrofitted with PV panels at any time. Most reputable SA installers recommend a hybrid inverter from the start, even if you are not adding panels immediately. Ensure the inverter's MPPT capacity matches your planned solar array size.