How to Choose Solar Panels and Batteries to Run a 100kWh Load 24/7: Full Guide with Examples
If you’re planning to power a 100kWh load continuously (24/7) using solar panels and a battery energy storage system (BESS), it’s not as simple as just multiplying watts. You need to factor in weather conditions, seasonal sunlight availability, cloudy days, and energy efficiency. This blog will guide you step-by-step on how to size your system properly using formulas, examples, and visual data.
???? What You’ll Learn:
- How to calculate required solar panel capacity
- Why yearly weather data is critical
- How to handle cloudy days and winter months
- Battery sizing for different backup durations
- Example formulas and real-world values
???? Step 1: Understand Your Load
Let’s say your system must support a 100 kWh per hour load.
- 24 hours/day × 100 kWh = 2,400 kWh per day
- That’s your daily energy demand from solar + battery.
???? Step 2: Analyze Your Location’s Solar Irradiance
Your geographic location heavily influences how much sunlight you receive—measured in Peak Sun Hours (PSH).
| Location | Peak Sun Hours |
|---|---|
| Phoenix, USA | 6.5 PSH |
| New Delhi, India | 5.5 PSH |
| London, UK | 2.8 PSH |
???? You can get this data from tools like PVWatts, NASA SSE, or Solcast.
???? Step 3: Calculate Required Solar Panel Capacity
Formula:
textCopyEditRequired Solar Capacity (kW) = Daily Load (kWh) ÷ (PSH × Derating Factor)
- Daily Load = 2,400 kWh
- Derating factor (system losses) = ~0.8
| Season | PSH | Required Solar Capacity |
|---|---|---|
| Summer | 6.5 | 2,400 ÷ (6.5 × 0.8) ≈ 462 kW |
| Winter | 4.0 | 2,400 ÷ (4.0 × 0.8) ≈ 750 kW |
| Cloudy Days | 2.5 | 2,400 ÷ (2.5 × 0.8) ≈ 1,200 kW |
????️ Why Consider Cloudy Days?
Even if your area has high annual irradiance, you’ll still face days with poor sun exposure. For mission-critical applications, your system must:
- Be oversized for worst-case scenarios.
- Include battery backup for 1–3 days.
- Use hybrid systems (e.g., gensets or grid backup) if needed.
❄️ Considerations for Winter Months
Winter brings:
- Lower sun angles
- Shorter daylight
- Snow cover (for northern regions)
???? This reduces effective PSH and increases your dependence on storage or supplemental power.
⚡ Step 4: Size the BatteryEnergy Storage System for Backup
Battery Energy Storage System should store enough energy to power the load during non-sunny hours or failures.
Formula:
textCopyEditBattery Capacity (kWh) = (Daily Load × Days of Autonomy) ÷ (DoD × Efficiency)
- Daily Load = 2,400 kWh
- Depth of Discharge (DoD) = 0.8
- Round-trip Efficiency = 0.9
| Backup Duration | Required Battery Capacity |
|---|---|
| 1 Day | 2,400 ÷ (0.8 × 0.9) ≈ 3,333 kWh |
| 2 Days | 4,800 ÷ (0.8 × 0.9) ≈ 6,667 kWh |
| 3 Days | 7,200 ÷ (0.8 × 0.9) ≈ 10,000 kWh |
✅ Tips for Choosing Solar Panels
- ✔️ Use Tier-1 panels with high efficiency (≥21%)
- ✔️ Consider bifacial panels if space allows
- ✔️ Use anti-reflective coating for dust-heavy areas
- ✔️ Install with adjustable tilt for seasonal optimization
✅ Tips for Choosing Batteries Cells for BESS
- ✔️ Choose Lithium Iron Phosphate (LFP) for safety and long life
- ✔️ Look for modular scalability
- ✔️ Integrate with a good BMS and EMS
- ✔️ Use temperature-controlled enclosures for extreme climates
???? Hybrid Solutions for Reliability
When powering a 100kWh continuous load, consider a hybrid setup:
- ???? Solar + Battery + Diesel: For industrial backup
- ???? Solar + Grid + Battery: For grid-tied systems
- ????️ Solar + Wind + Battery: For off-grid redundancy
???? Real Use Case Example
Scenario:
- Location: Northern India
- PSH (winter): 4 hours
- Load: 100kWh × 24 = 2,400kWh/day
- Solar Size = 2,400 ÷ (4.0 × 0.8) = 750 kW
- Battery for 2 days = 2,400 × 2 ÷ (0.8 × 0.9) ≈ 6,667 kWh
???? FAQs
Q: Can I go without batteries?
A: Only if your load is flexible or you remain connected to the grid.
Q: Should I oversize the battery or the solar array?
A: Both, depending on your climate. Cloudy regions need higher solar oversizing.
Q: What’s better—LFP or NMC batteries?
???? Conclusion
Designing a solar + battery system for a 100kWh 24/7 load isn’t just about matching numbers—it’s about planning for the worst day of the year, not the best. Location-specific solar data, battery autonomy, system losses, and seasonal variations must all be part of your sizing strategy.
