Solar System Sizer

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

How to use — Solar System Sizer

Select your country — this loads local electricity tariffs, sun hours (peak solar hours per day), seasonal hemisphere adjustment, and currency.
Enter your average monthly electricity usage in kWh. Find this on your electricity bill, or use the Load Planner tab to calculate it.
Set the percentage of your usage you want solar to cover — 80–100% for an off-grid-capable system, 50–60% for a daytime self-consumption system.
Review the recommended solar panel capacity (kWp), inverter size (kVA), and battery storage (kWh).
Adjust the system size sliders to see how different configurations affect estimated generation and self-sufficiency.
Battery sizing accounts for your desired backup hours during load shedding — increase battery capacity for longer backup.

💡 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.

How to use — Load Planner

Add each major appliance in your home — geyser, fridge, TV, lights, AC, pool pump.
Enter the wattage (found on the appliance label or manual) and estimated daily hours of use.
The calculator totals your daily kWh consumption and monthly usage.
Identify your biggest loads — typically geyser (2–3kW), AC (1–3kW), and pool pump (0.75–1.5kW). These are also the best targets for solar automation.
Use the results to fill in the System Sizer tab with an accurate monthly usage figure.

🔌 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.

How to use — Savings & Return on Investment

Enter your current average monthly electricity bill in your local currency.
Enter the estimated total installed cost of your solar system (get quotes from at least 3 installers).
Set the percentage of generated solar you expect to self-consume vs export (if your utility allows export).
The calculator shows annual savings, payback period in years, and 10-year and 25-year return on investment.
Electricity tariff escalation (typically 8–12% per year in South Africa) is factored in — this significantly improves long-term ROI.
Use this tab to compare different system sizes and find the sweet spot between upfront cost and savings.

💰 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.

How to use — Load Shedding / Backup Sizer

Select your load shedding stage — higher stages mean more frequent and longer outages to plan for.
Enter the loads you need to run during an outage: critical loads only (lights, router, fridge) or full home.
Enter total critical load in watts and the number of backup hours you want per outage.
Set your battery depth of discharge limit — 80% is recommended for lithium batteries to preserve lifespan.
The calculator shows the minimum battery capacity needed (kWh) to meet your backup requirement.
For South Africa: Stage 4–6 load shedding can mean 8–12 hours without power per day. Plan your battery for the worst stage you regularly experience.

🔌 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.