Can Solar Power Your Whole House?

What "Whole House" Actually Means

There are four distinct scenarios most homeowners mean when they ask this question:

• 100% annual energy independence: the system produces enough over a year to match total consumption, with grid export in summer offsetting winter imports
• Complete off-grid operation: never use grid power — requires significantly more battery capacity and system redundancy
• Essential load coverage: solar powers critical loads (lights, fridges, internet, security) while heavy loads use grid during peak demand
• Daytime independence: solar covers all daytime consumption while grid supplements at night — minimises battery investment

Household Energy Consumption Breakdown

System Sizing for Whole House Coverage

Powering an entire house requires matching both production and peak demand:

• Panels: each kW produces ~4.5–6 kWh daily in SA. A home using 30 kWh/day needs 5–7 kW of panels
• Inverter: must handle peak simultaneous load — 5kW for managed loads, 8–10kW for households running multiple heavy appliances
• Batteries: for overnight coverage, match expected consumption during non-production hours. A 10 kWh overnight need requires ~12–14 kWh usable battery capacity
• Typical example: 8kW panels + 8kW inverter + 15kWh battery for a 900 kWh/month household (R220,000–R280,000)

The Battery Challenge

Batteries are the enabling technology — and the primary cost challenge:

• Cost: quality lithium batteries cost R7,000–R10,000 per usable kWh — a 15kWh system adds R105,000–R150,000
• Usable capacity: batteries shouldn't discharge below 10–20%. A 15kWh battery gives only 12–13.5 kWh usable
• Degradation: batteries lose ~20–30% capacity over 10 years — size for future state, not just today
• Extended cloudy periods: three overcast days at 50% production may require 30+ kWh stored for full independence

Grid-Tied vs Off-Grid for Whole House

The approach differs significantly between configurations:

• Grid-tied hybrid (most common): uses grid as backup, exports excess for credit, smaller batteries needed, seamless load management
• Off-grid: complete Eskom independence, but requires larger battery banks, backup generator for extended cloudy periods, higher upfront cost
• Most urban SA homeowners choose grid-tied hybrid — extensive solar coverage with grid backup for exceptional circumstances
• True off-grid makes sense primarily for remote properties or those with extreme energy independence goals