The most common question in solar planning: "My monthly bill is $X — what size solar system do I need?" The answer depends on two factors: your local electricity tariff rate (price per kWh) and your location's solar resource (specific yield in kWh/kWp).
This guide provides ready-to-use lookup tables for major global markets. Find your monthly bill amount and tariff rate, then read directly the system size you need.
The Formula
Step 2: System Size (kWp) = Monthly kWh ÷ Monthly Specific Yield (kWh/kWp)
Specific yield is the amount of energy produced per installed kWp. It varies by climate:
- Tropical (0-20°): 145 kWh/month/kWp (1,740 kWh/year)
- Subtropical / Arid (20-35°): 135 kWh/month/kWp (1,620 kWh/year)
- Temperate (35-50°): 110 kWh/month/kWp (1,320 kWh/year)
- High Latitude (50°+): 85 kWh/month/kWp (1,020 kWh/year)
Conversion Tables by Market
Each table below shows: Typical monthly bill → Monthly kWh → Required kWp for both temperate and subtropical specific yields. Find your market and bill amount.
USA Market ($0.12/kWh average)
| Monthly Bill | Monthly kWh | System Size (Temperate) | System Size (Subtropical) |
|---|---|---|---|
| $75 | 625 | 5.5 kWp | 4.5 kWp |
| $100 | 833 | 7.5 kWp | 6.0 kWp |
| $125 | 1,042 | 9.5 kWp | 7.5 kWp |
| $150 | 1,250 | 11.5 kWp | 9.5 kWp |
| $200 | 1,667 | 15.0 kWp | 12.5 kWp |
| $250 | 2,083 | 19.0 kWp | 15.5 kWp |
| $300 | 2,500 | 23.0 kWp | 18.5 kWp |
UK Market (£0.28/kWh average)
| Monthly Bill | Monthly kWh | System Size (Temperate, UK) |
|---|---|---|
| £60 | 214 | 2.0 kWp |
| £80 | 286 | 2.5 kWp |
| £100 | 357 | 3.5 kWp |
| £120 | 429 | 4.0 kWp |
| £150 | 536 | 5.0 kWp |
| £200 | 714 | 6.5 kWp |
| £300 | 1,071 | 10.0 kWp |
Germany Market (€0.32/kWh average)
| Monthly Bill | Monthly kWh | System Size (Temperate) |
|---|---|---|
| €60 | 188 | 2.0 kWp |
| €80 | 250 | 2.5 kWp |
| €100 | 313 | 3.0 kWp |
| €130 | 406 | 4.0 kWp |
| €160 | 500 | 5.0 kWp |
| €200 | 625 | 5.5 kWp |
| €250 | 781 | 7.0 kWp |
| €320 | 1,000 | 9.0 kWp |
Australia Market (A$0.25/kWh average)
| Monthly Bill | Monthly kWh | System Size (Subtropical) |
|---|---|---|
| A$100 | 400 | 3.0 kWp |
| A$150 | 600 | 4.5 kWp |
| A$200 | 800 | 6.0 kWp |
| A$250 | 1,000 | 7.5 kWp |
| A$300 | 1,200 | 9.0 kWp |
| A$400 | 1,600 | 12.0 kWp |
| A$500 | 2,000 | 15.0 kWp |
India Market (Rs. 7/kWh average)
| Monthly Bill | Monthly kWh | System Size (Subtropical) |
|---|---|---|
| Rs. 1,500 | 214 | 1.5 kWp |
| Rs. 2,500 | 357 | 2.5 kWp |
| Rs. 3,500 | 500 | 4.0 kWp |
| Rs. 5,000 | 714 | 5.5 kWp |
| Rs. 7,500 | 1,071 | 8.0 kWp |
| Rs. 10,000 | 1,429 | 10.5 kWp |
| Rs. 15,000 | 2,143 | 16.0 kWp |
Pakistan Market (Rs. 50/kWh average)
| Monthly Bill | Monthly kWh | System Size (Subtropical) |
|---|---|---|
| Rs. 10,000 | 200 | 1.5 kWp |
| Rs. 20,000 | 400 | 3.0 kWp |
| Rs. 30,000 | 600 | 4.5 kWp |
| Rs. 40,000 | 800 | 6.0 kWp |
| Rs. 50,000 | 1,000 | 7.5 kWp |
| Rs. 75,000 | 1,500 | 11.0 kWp |
| Rs. 100,000 | 2,000 | 15.0 kWp |
UAE Market (AED 0.45/kWh average)
| Monthly Bill | Monthly kWh | System Size (Arid/Subtropical) |
|---|---|---|
| AED 200 | 444 | 3.5 kWp |
| AED 350 | 778 | 6.0 kWp |
| AED 500 | 1,111 | 8.5 kWp |
| AED 750 | 1,667 | 12.5 kWp |
| AED 1,000 | 2,222 | 16.5 kWp |
| AED 1,500 | 3,333 | 25.0 kWp |
How Tariff Types Affect Sizing
The tariff rate you pay per kWh depends on your utility's rate structure. The table assumes a flat tariff (same rate all day). However, many markets use tiered or time-of-use (TOU) rates:
| Tariff Type | How It Works | Sizing Impact |
|---|---|---|
| Flat Rate | Same $/kWh regardless of usage level or time | Simple — use the rate from your bill directly |
| Tiered (Inclining Block) | Rate increases as you consume more kWh per month | Use the highest tier rate for sizing because you want to offset the most expensive kWh |
| Tiered (Declining Block) | Rate decreases as you consume more (commercial) | Use the average effective rate = total bill ÷ total kWh |
| Time-of-Use (TOU) | Different rates for peak, off-peak, and shoulder periods | Size for peak period offset. If peak rate is $0.30 and off-peak is $0.10, you should size to cover peak consumption first |
| Feed-in Tariff (FiT) | You get paid for exported solar energy at a specific rate | If FiT is near retail rate, size to offset 100%. If FiT is low, consider self-consumption optimization and slightly undersizing |
Worked Examples
Example 1: Los Angeles, USA
Monthly bill: $200. Tariff: $0.12/kWh (flat). Monthly kWh: $200 ÷ 0.12 = 1,667 kWh. Climate: Temperate (coastal LA). Monthly yield: 110 kWh/kWp. System size: 1,667 ÷ 110 = 15.2 → 15.5 kWp. Panels needed: 29 × 550W (15.95 kWp). Inverter: 15 kW.
Example 2: Lahore, Pakistan
Monthly bill: Rs. 45,000. Tariff: Rs. 50/kWh (tiered, using highest slab). Monthly kWh: 45,000 ÷ 50 = 900 kWh. Climate: Subtropical. Monthly yield: 135 kWh/kWp. System size: 900 ÷ 135 = 6.7 → 7.0 kWp. Panels needed: 13 × 550W (7.15 kWp). Inverter: 6 kW.
Example 3: London, UK
Monthly bill: £140. Tariff: £0.28/kWh. Monthly kWh: 140 ÷ 0.28 = 500 kWh. Climate: Temperate. Monthly yield: 110 kWh/kWp. System size: 500 ÷ 110 = 4.5 → 4.5 kWp. Panels needed: 9 × 550W (4.95 kWp). Inverter: 5 kW.
Related Guides
- Calculate Solar System Size From Your Bill
- Solar Panel Wattage Guide: Which Wattage in 2026?
- Solar Inverter Sizing Guide: Match Inverter to Array
Convert your bill instantly
Open the Solar System Size Calculator →Data sources: US EIA 2025 residential electricity rates, UK Ofgem price cap 2026, Germany BDEW Strompreis 2025, Australian Energy Regulator 2025-26, Indian CEA tariff data, Pakistan NEPRA 2025-26 slab rates, UAE DEWA 2025 tariffs. Specific yield from NREL PVWatts, European Commission JRC PVGIS. System sizes are recommendations only.
Last updated: July 2026 | Browse all guides