Quick Verdict: Solar + battery delivers higher total savings (£1,600/year vs £900/year) and better energy independence, but solar-only offers superior ROI (350% vs 275%) and faster payback (6-7 years vs 8-9 years). Best strategy: Install solar first (£5,500), let it pay for itself, then add battery (£5,000) in years 6-8 using solar profits.
Side-by-Side Comparison
| Factor | Solar Only (4kW) | Solar + Battery (4kW + 10kWh) | Difference |
|---|---|---|---|
| Upfront Cost | £5,500 | £10,700 | +£5,200 |
| Year 1 Savings | £900 | £1,600 | +£700/year |
| Self-Consumption | 30% | 65% | +35% |
| Bill Reduction | 45-55% | 70-85% | +25-30% |
| Payback Period | 6.1 years | 6.7 years | +0.6 years |
| 25-Year ROI | 350% | 275% | Solar better |
| 25-Year Profit | £25,000 | £35,000 | +£10,000 |
| Energy Independence | 30% | 75-85% | Much higher |
| Grid Resilience | No backup | 4-12hr backup | Power cuts covered |
Cost Breakdown
Solar Only (4kW System)
- Panels: £3,500
- Inverter: £1,200
- Installation: £800
- Total: £5,500 (0% VAT)
- Ongoing costs: £0
Solar + Battery (4kW + 10kWh)
- Panels: £3,500
- Hybrid inverter: £2,000
- 10kWh battery: £4,000
- Installation: £1,200
- Total: £10,700 (0% VAT on everything when installed together)
- Ongoing costs: £0
Battery Premium: £5,200 extra
Savings Comparison
How Solar-Only Saves Money
Total: £900/year
- Bill reduction: £299 (1,080 kWh self-consumed at 27.69p)
- Export income: £302 (2,520 kWh exported at 12p)
- Limitation: Only 30% self-consumption - you export 70% at low rates
How Solar + Battery Saves Money
Total: £1,600/year
- Increased self-consumption: £598 (2,160 kWh at 27.69p instead of exporting at 12p)
- Time-shifting savings: £600 (charging battery overnight at 7.5p, using at 27.69p peak)
- Reduced export: £108 (900 kWh at 12p)
- Total savings: £1,306/year
🔋 Get Exact ROI for Both Options
Our Pro calculator compares solar-only vs solar+battery for your specific home, showing exact payback periods and 25-year profits for both scenarios.
Compare Both Options (£4.99) →When Solar-Only Makes More Sense
- Budget constraints: £5,500 is half the cost of combined system
- Maximising ROI: 350% vs 275% - solar-only returns more per pound invested
- Quick payback: 6.1 years vs 6.7 years
- Low consumption homes: If you use <12kWh/day, battery won't cycle fully
- No smart tariff access: Without cheap overnight rates, battery benefit is lower
- Add battery later: Can retrofit battery in 3-5 years when prices drop further
When Solar + Battery Makes More Sense
- Energy independence priority: Want 75-85% self-sufficiency vs 30%
- Power cut resilience: Battery provides 4-12 hours backup power
- Smart tariff available: Octopus Go (7.5p overnight) maximises battery ROI
- High evening usage: Cook, watch TV, charge devices 6-11pm
- Future EV plans: Battery + cheap overnight charging = major savings
- Rising electricity prices: Locking in savings now hedges against future price rises
The Staged Approach (Best Value)
Most financial planners recommend this strategy:
Stage 1: Install Solar Only (Year 0)
- Investment: £5,500
- Annual savings: £900
- Payback: 6.1 years
- By year 6: System has paid for itself
Stage 2: Add Battery (Year 6-8)
- Solar has generated £6,000-8,000 profit by now
- Battery cost: £5,000 (likely cheaper by then)
- Funded entirely by solar profits - zero new money needed
- Combined savings jump to £1,600/year
Why This Works Best:
- Lower initial outlay (£5,500 vs £10,700)
- Solar pays for battery - no new capital needed
- Battery prices dropping 5-10%/year - cheaper to wait
- Battery technology improving - better batteries available later
- Test your actual usage first - size battery accurately
- Overall ROI: 320% vs 275% (combined upfront)
Real Example: 3-Bedroom Semi in Bristol
Solar Only Scenario
- 2026: Install 4kW solar (£5,500)
- 2026-2032: Save £900/year (£6,300 cumulative)
- 2032: System paid for itself
- 2032-2051: Pure profit (£19,000)
- 25-year total profit: £25,300
- ROI: 360%
Solar + Battery Upfront Scenario
- 2026: Install 4kW solar + 10kWh battery (£10,700)
- 2026-2033: Save £1,600/year (£12,800 cumulative)
- 2033: System paid for itself
- 2033-2051: Pure profit (£23,200)
- 25-year total profit: £36,000
- ROI: 280%
Staged Approach Scenario
- 2026: Install 4kW solar (£5,500)
- 2026-2032: Save £900/year (£6,300)
- 2032: Add 10kWh battery using solar profits (£4,500 by then)
- 2032-2051: Save £1,600/year (£30,400)
- 25-year total profit: £36,700
- ROI: 345%
Winner: Staged approach delivers highest ROI while requiring lowest initial capital
Battery Size Comparison
If you do choose solar + battery upfront, sizing matters:
| Battery Size | Additional Cost | Additional Savings/Year | ROI on Battery | Best For |
|---|---|---|---|---|
| 5kWh | +£3,500 | +£450 | 285% | Small homes, low usage |
| 10kWh | +£5,000 | +£700 | 310% | Most homes |
| 13.5kWh | +£7,000 | +£850 | 270% | Large homes, EVs |
10kWh offers the best balance of cost vs benefit for typical UK homes.
Future Battery Price Trends
Battery costs have fallen dramatically and continue dropping:
- 2020: £800/kWh (10kWh = £8,000)
- 2023: £600/kWh (10kWh = £6,000)
- 2026: £500/kWh (10kWh = £5,000)
- 2028 (projected): £400/kWh (10kWh = £4,000)
- 2030 (projected): £350/kWh (10kWh = £3,500)
Waiting 2-3 years to add battery could save £1,000-1,500, strengthening the staged approach argument.
Compare Both Options for Your Home
Get exact payback periods and 25-year profits for solar-only vs solar+battery based on your postcode and electricity usage.
Get Battery Comparison (£4.99) →Or start with our free solar calculator