🔋 Battery Storage

Solar battery storage system • Watten, Scottish Highlands

🔋

Battery Storage System

Installation Scheduled: February 2026

Hanchu API Connected
System ready • Solar rated: 7.0kW • Temp: 0.0°C
Planned Capacity
18.8 kWh
2x Hanchu 9.4kWh
Solar System
4.8 kW
12 x 400W Panels
Expected Benefit
+40%
Self-Sufficiency
📊 Battery Simulation (Based on Last 30 Days)

What would an 18.8kWh battery save you based on your actual usage patterns?

💷 Projected Savings
£3.85
Per Month
£46.86/year
⚡ Grid Avoided
1.1 kWh
Per Day (avg)
19.7 kWh over 18 days
☀️ Solar Captured
1.2 kWh
Per Day (avg)
Currently exported, would be stored
🌱 Self-Sufficiency
4%
→
6%
Current → With Battery
📅 Est. Payback
106.7 years
At ~£5,000 system cost
📈 Simulation Details
Assumptions:
  • 18.8kWh capacity (2x Hanchu 9.4kWh)
  • 90% usable capacity (10-100% DoD)
  • 90% round-trip efficiency
  • Blended rate: 28.42p/kWh
Notes:
  • Based on your actual 30-day history
  • Real savings may be higher with Cosy tariff optimisation
  • Doesn't account for seasonal variation
  • Summer months will show better returns
⚡ Cosy Tariff Arbitrage

Extra savings by charging during cheap Cosy periods (14.33p) and discharging during Peak (43.83p)

💰 Arbitrage Spread
29.5p/kWh
Peak (43.83p) - Cosy (14.33p)
After 90% efficiency: 26.6p/kWh profit
🔄 Daily Arbitrage
£2.25
Per Day (est.)
Using ~8.5 kWh for arbitrage
🎯 Combined Savings
£71.24
Per Month
Solar + Arbitrage: £866.70/year
📅 Improved Payback
5.8 years
With Arbitrage
vs 106.7 years solar only
📊 Monthly Savings Breakdown
Solar Storage: £3.85
Cosy Arbitrage: £67.38
Total: £71.24/month
⏰ Optimal Battery Schedule for Cosy Tariff
🔋 CHARGE (Cosy: 14.33p)
  • 04:00 - 07:00 (3 hours)
  • 13:00 - 16:00 (3 hours)
  • 22:00 - 00:00 (2 hours)
⚡ DISCHARGE (Peak: 43.83p)
  • 16:00 - 19:00 (3 hours)
  • Power home from battery
  • Avoid expensive peak grid
☀️ SOLAR PRIORITY
  • Daytime: Store excess solar
  • Evening: Use solar first
  • Export only when full
💷 Battery Savings by Tariff

Compare potential battery savings across different Octopus tariffs

✓ Your Current Tariff
Octopus Cosy
Battery savings: £76.91/month
🏆 Best for Battery
Octopus Cosy
Battery savings: £76.91/month
Tariff Spread Arbitrage Solar Monthly Payback
🥇 Octopus Cosy CURRENT
Best for heat pumps
 29.5p £67.38 £9.53 £76.91 5.3 yrs
🥈 Octopus Flux
Best for battery export
 22.6p £51.58 £9.25 £59.00 7.0 yrs
🥉 Octopus Go
Best for EV charging
 22.6p £51.71 £6.49 £58.21 7.1 yrs
💡
Key Insights:
  • Cosy has the best arbitrage spread (29.5p) making it excellent for battery storage
  • Go has cheap overnight rates but smaller spread for arbitrage
  • Flux offers better export rates which boosts returns if you export
  • Agile rates vary - can be very profitable on high-spread days
  • Flexible has no arbitrage benefit (flat rate)
📅 Seasonal Projections

Projected battery savings across seasons based on Scottish Highlands solar potential and heating patterns

☀️ Annual Solar
2,685 kWh
Projected generation
🔥 Annual Heat Pump
6,552 kWh
Projected usage
💷 Annual Battery Savings
£575.10
Projected total
📅 Realistic Payback
8.7 years
Seasonal adjusted
❄️ Winter
Dec - Feb
Minimal solar, high heating
Solar
1.5 kWh/day
Heat Pump
35.0 kWh/day
Grid Avoided
16 kWh
Battery Savings
£206.32
Solar vs Demand 3%
🌸 Spring
Mar - May
Good solar, moderate heating
Solar
8.0 kWh/day
Heat Pump
15.0 kWh/day
Grid Avoided
246 kWh
Battery Savings
£140.02
Solar vs Demand 35%
☀️ Summer
Jun - Aug
Peak solar, minimal heating
Solar
15.0 kWh/day
Heat Pump
2.0 kWh/day
Grid Avoided
364 kWh
Battery Savings
£79.02
Solar vs Demand 150%
🍂 Autumn
Sep - Nov
Declining solar, rising heating
Solar
5.0 kWh/day
Heat Pump
20.0 kWh/day
Grid Avoided
123 kWh
Battery Savings
£149.74
Solar vs Demand 18%
📊 Seasonal Comparison
£206
❄️
Winter
£140
🌸
Spring
£79
☀️
Summer
£150
🍂
Autumn
🌍
Scottish Highlands Factors:
  • Summer: Up to 18+ hours daylight, solar panels can generate 15+ kWh/day. Battery captures excess for evening use.
  • Winter: Only ~7 hours daylight with low sun angle. Battery value comes mainly from tariff arbitrage, not solar storage.
  • Heat Pump: Major consumer in winter (~35 kWh/day), minimal in summer (~2 kWh for hot water only).
  • Best ROI: Summer months provide best battery returns due to excess solar capture.