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Solar Battery Payback Calculator

Calculate whether adding a battery storage system to your solar panels is financially worthwhile.

Solar Battery Payback Calculator

Affects self-consumption rate

Storage capacity in kWh

Installed cost

Price cap: 24.5p

SEG rates: 12-20p

Additional Daily Self-Consumption

4.5

kWh/day from battery

Annual Battery Savings

£156.75

per year

Battery Cost

£5000.00

Cost per kWh: £1000.00

Payback Period

31.9

years

Solar Only vs Solar + Battery

Solar Only

Daily Self-Consumption6.8 kWh
Daily Export8.3 kWh
Daily Savings£2.90
Annual Savings£1060.12
System Cost£10000.00

Solar + Battery

Daily Self-Consumption11.3 kWh
Daily Export3.8 kWh
Daily Savings£3.33
Annual Savings£1216.88
System Cost£15000.00

Battery adds: £156.75/year benefit, payback in 31.9 years

15-Year Cumulative Return

Year 0p0.0
Year 1 (Capacity: 4.97 kWh)p-484325.0
Year 2 (Capacity: 4.95 kWh)p-468728.4
Year 3 (Capacity: 4.93 kWh)p-453209.7
Year 4 (Capacity: 4.90 kWh)p-437768.7
Year 5 (Capacity: 4.88 kWh)p-422404.8
Year 6 (Capacity: 4.85 kWh)p-407117.8
Year 7 (Capacity: 4.83 kWh)p-391907.2
Year 8 (Capacity: 4.80 kWh)p-376772.7
Year 9 (Capacity: 4.78 kWh)p-361713.8
Year 10 (Capacity: 4.76 kWh)p-346730.3
Year 11 (Capacity: 4.73 kWh)p-331821.6
Year 12 (Capacity: 4.71 kWh)p-316987.5
Year 13 (Capacity: 4.68 kWh)p-302227.6
Year 14 (Capacity: 4.66 kWh)p-287541.4
Year 15 (Capacity: 4.64 kWh)p-272928.7

Battery breaks even in year -1. After 15 years: p-272928.7 return

Battery Benefits

  • Increase solar self-consumption from 45% to 75-85%
  • Save an extra £156.75 per year
  • Payback period: 31.9 years
  • Energy independence: use solar power in evening
  • Backup power in grid outages (if hybrid system)
  • Flatten your consumption profile
  • Export less = receive less low-rate export income
  • Battery warranty: typically 10-15 years

💡 Battery Optimization

  • For day-heavy usage: smaller battery (3-5 kWh) is more cost-effective
  • For evening-heavy usage: larger battery (8-13.5 kWh) captures morning generation
  • Install smart controls to charge battery when export tariff is low
  • Time your largest loads (laundry, EV charging) to battery discharge hours
  • Consider time-of-use tariffs: charge battery during cheap hours, discharge during peak
  • Monitor battery degradation (should be <1% per year)
  • Pair with smart meter to see real-time generation and usage
  • Check if your installer offers battery upgrades after purchase

When to Add Battery?

Add battery now if:

  • Payback period is under 10 years
  • You have evening-heavy usage
  • Export tariff is very low (under 10p/kWh)
  • You want energy independence
  • Grid outages are frequent in your area

Wait and add later if:

  • Payback period is over 12 years
  • You have day-heavy usage (most self-consumed already)
  • Battery prices are dropping (historically 5-10% per year)
  • Your household usage pattern may change

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