Solar Calculator — Panel Sizing, Battery & ROI for South Africa & International

Solar System Sizer

Enter your electricity bill and location to get a complete system recommendation — panels, inverter, and battery. No bias, no lead capture.

💡 Your Electricity

Average Monthly Bill

Enter your average monthly electricity bill in the selected currency

OR — I know my monthly kWh usage

Leave blank to calculate from bill above

Region / Province / State

Roof Orientation

🧭 North-facing
Best

🌅East
−15%

🌇West
−15%

🏠Multi
Custom

Panels per direction

🧭 NORTH

×1.00

🌅 EAST

×0.85

🌇 WEST

×0.85

Total: 16 Blended factor: 0.925

Panel Wattage

Sizing Goal

Battery Backup Required

Recommended System

– kW

–

Solar Panels

–panels

–

Inverter Size

–kW

+25% headroom on system

Battery (recommended)

–kWh

–

Battery Units

–

× 10.2 kWh LiFePO4

Daily Production

–kWh

avg good day

Winter Production

–kWh

worst month estimate

Monthly Production

–kWh

–

Your Daily Usage

–kWh

–

📋 Sizing Notes

–

🏠 Real-world reference: A 10kW system with two strings in Pretoria (7kW north house roof + 5.5kW garage) produces 45–50 kWh/day summer and 30–35 kWh/day winter.

Household Load Planner

Build your actual daily load appliance by appliance. Toggle and adjust hours. Feed these results into the System Sizer for an accurate panel count.

🔌 Appliances

	Appliance	W	Hrs/day	kWh/day

Total Daily Load

0.0 kWh

–

Peak Simultaneous Load

–W

min inverter sizing

Monthly kWh

–

× 30 days

Estimated Bill

–

at selected rate

Biggest Consumer

–

highest kWh/day item

📊 Breakdown by Category

Savings & Return on Investment

See your payback period, annual savings, and why rising electricity prices make solar increasingly valuable every year.

💰 Your Numbers

Total Installed System Cost

Typical SA 2026: ~R75k–R120k (5kW no battery) · R130k–R200k (with 10kWh battery)

Current Monthly Electricity Bill

% of Bill Offset by Solar

85%

Annual Electricity Price Increase

12%

SA historical: 12–15%/yr · UK: ~5–8%/yr · AUS: ~4–6%/yr

Panel Degradation per Year

0.5%

Industry standard: 0.5%/yr. Most panels warrantied at 80% output after 25 years.

Solar Tax Rebate –

Payback Period

– yrs

–

Net Cost After Rebate

–

after any applicable rebate

Year 1 Monthly Saving

–

on electricity bill

10-Year Net Saving

–

vs staying on grid

25-Year Net Saving

–

panel warranty lifetime

📅 Year-by-Year Savings

Year	Grid Rate	Monthly Saving	Annual Saving	Cumulative

Load Shedding / Backup Sizer

Size a battery and inverter just for backup power during outages. Select what must stay on and for how long.

🔌 What Must Stay On?

Outage Duration

Battery Chemistry

⚡ Lithium (LiFePO4) batteries deliver 85–90% of rated capacity safely. Gel/AGM should only use 50% to protect lifespan. This calculator applies the correct depth-of-discharge automatically.

Battery Capacity Needed

– kWh

–

Total Load

–W

simultaneous draw

Minimum Inverter

–kVA

peak + 25% headroom

Raw kWh Needed

–kWh

load × duration

Rated Capacity Required

–kWh

–

🛒 Recommendation

Select appliances above.

🔋 Real-world reference: A 10.2 kWh LiFePO4 battery with a 5kW inverter running lights + WiFi + fridge + TV will last 6–8 hours. Adding air conditioning reduces this to 2–3 hours.