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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TR24 (Isles of Scilly)

See if solar pays off for you in Isles of Scilly — price, savings and payback in under a minute (official UK data).

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Change the settings below to see how costs and savings work for your situation.

System Size

Roof Direction

Battery Storage

Export Value

Your Numbers

Break-even
11.1 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£917
What you save every year
Profit Over 25 Years
£12,747
After paying itself off, you're this much ahead

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How we calculate this

Solar generation: Based on typical south-facing roof at 35° angle. We account for weather, dirt, and system losses (14%).

How much you'll use directly:

  • Without battery: You'll use about 40% of what you generate. The rest gets sold back to the grid.
  • With 5 kWh battery: You'll use about 70% (battery stores extra for evening use).
  • With 10 kWh battery: You'll use about 75% (more storage means less exported).
  • Panel-only payback: Bigger systems don’t shorten payback—cost and savings rise together per kW.
  • Battery & payback: Batteries raise self-use and cut bills, but added hardware cost often lengthens break-even at typical UK rates.
  • When a battery can still make sense:
    • Evening-heavy usage patterns
    • Time-of-use tariffs / cheap night rates
    • Low export rate vs. high unit rate
    • Heat pump or EV charging synergy
    • Optional backup/resilience (system-dependent)
    • Lower evening-hour CO₂ vs. grid

Costs: Battery prices are typically £700 per kWh. Export tariffs vary by supplier (usually 5–15p per kWh).

Grid connection: Systems up to about 3.7 kW typically need just a notification (G98). Larger systems may need permission (G99).

These are typical values based on average usage patterns. Your actual results will vary based on your roof, shading, and how you use electricity.

Your area in context

In Southern Western, the current unit rate is 26.82p/kWh with a 54.03p/day standing charge. Your postcode’s south-facing sunshine yield is 1096 kWh/kW — 83 above the regional median (1013).

Read the full story

A typical roof here lands around 5.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 1096 kWh per year on a south-facing roof. We value self-used electricity at 26.8p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.8p/kWh
Standing charge
54.0p/day
Sunshine yield (south)
1096 kWh/kW
Export price (baseline)
10p/kWh

Browse the scenarios below. Each battery size has its own expand — open the one that matches your plan (or just explore). For each system size (2–8 kW) we show annual output, how much you use directly, what gets exported, annual benefit, upfront cost, break-even, and a 20-year net. Negative numbers are possible — that’s the honest trade-off when adding more battery than your usage profile justifies.

No battery 5 kW example → Annual benefit: £917, Upfront: £10,173, Break-even: 11.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2192 kWh 877 kWh 1315 kWh £235 £132 £367 £4,069 11.1 yrs £3,265
3 kW 3288 kWh 1315 kWh 1973 kWh £353 £197 £550 £6,104 11.1 yrs £4,898
4 kW 4384 kWh 1754 kWh 2631 kWh £470 £263 £733 £8,138 11.1 yrs £6,531
5 kW 5481 kWh 2192 kWh 3288 kWh £588 £329 £917 £10,173 11.1 yrs £8,163
6 kW 6577 kWh 2631 kWh 3946 kWh £706 £395 £1,100 £12,207 11.1 yrs £9,796
7 kW 7673 kWh 3069 kWh 4604 kWh £823 £460 £1,284 £14,242 11.1 yrs £11,428
8 kW 8769 kWh 3508 kWh 5261 kWh £941 £526 £1,467 £16,276 11.1 yrs £13,061

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

3 kWh battery 5 kW example → Annual benefit: £1,101, Upfront: £12,273, Break-even: 11.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2192 kWh 1315 kWh 877 kWh £353 £88 £440 £6,169 14.0 yrs £2,640
3 kW 3288 kWh 1973 kWh 1315 kWh £529 £132 £661 £8,204 12.4 yrs £5,010
4 kW 4384 kWh 2631 kWh 1754 kWh £706 £175 £881 £10,238 11.6 yrs £7,380
5 kW 5481 kWh 3288 kWh 2192 kWh £882 £219 £1,101 £12,273 11.1 yrs £9,750
6 kW 6577 kWh 3946 kWh 2631 kWh £1,058 £263 £1,321 £14,307 10.8 yrs £12,121
7 kW 7673 kWh 4604 kWh 3069 kWh £1,235 £307 £1,542 £16,342 10.6 yrs £14,491
8 kW 8769 kWh 5261 kWh 3508 kWh £1,411 £351 £1,762 £18,376 10.4 yrs £16,861

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

5 kWh battery 5 kW example → Annual benefit: £1,193, Upfront: £13,673, Break-even: 11.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2192 kWh 1535 kWh 658 kWh £412 £66 £477 £7,569 15.9 yrs £1,978
3 kW 3288 kWh 2302 kWh 986 kWh £617 £99 £716 £9,604 13.4 yrs £4,716
4 kW 4384 kWh 3069 kWh 1315 kWh £823 £132 £955 £11,638 12.2 yrs £7,455
5 kW 5481 kWh 3836 kWh 1644 kWh £1,029 £164 £1,193 £13,673 11.5 yrs £10,194
6 kW 6577 kWh 4604 kWh 1973 kWh £1,235 £197 £1,432 £15,707 11.0 yrs £12,933
7 kW 7673 kWh 5371 kWh 2302 kWh £1,440 £230 £1,671 £17,742 10.6 yrs £15,672
8 kW 8769 kWh 6138 kWh 2631 kWh £1,646 £263 £1,909 £19,776 10.4 yrs £18,411

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

7.5 kWh battery 5 kW example → Annual benefit: £1,221, Upfront: £15,423, Break-even: 12.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2192 kWh 1600 kWh 592 kWh £429 £59 £488 £9,319 19.1 yrs £449
3 kW 3288 kWh 2400 kWh 888 kWh £644 £89 £733 £11,354 15.5 yrs £3,298
4 kW 4384 kWh 3201 kWh 1184 kWh £858 £118 £977 £13,388 13.7 yrs £6,148
5 kW 5481 kWh 4001 kWh 1480 kWh £1,073 £148 £1,221 £15,423 12.6 yrs £8,997
6 kW 6577 kWh 4801 kWh 1776 kWh £1,288 £178 £1,465 £17,457 11.9 yrs £11,847
7 kW 7673 kWh 5601 kWh 2072 kWh £1,502 £207 £1,709 £19,492 11.4 yrs £14,696
8 kW 8769 kWh 6401 kWh 2368 kWh £1,717 £237 £1,954 £21,526 11.0 yrs £17,546

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

10 kWh battery 5 kW example → Annual benefit: £1,239, Upfront: £17,173, Break-even: 13.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2192 kWh 1644 kWh 548 kWh £441 £55 £496 £11,069 22.3 yrs £-1,154
3 kW 3288 kWh 2466 kWh 822 kWh £661 £82 £744 £13,104 17.6 yrs £1,770
4 kW 4384 kWh 3288 kWh 1096 kWh £882 £110 £992 £15,138 15.3 yrs £4,693
5 kW 5481 kWh 4110 kWh 1370 kWh £1,102 £137 £1,239 £17,173 13.9 yrs £7,616
6 kW 6577 kWh 4932 kWh 1644 kWh £1,323 £164 £1,487 £19,207 12.9 yrs £10,539
7 kW 7673 kWh 5755 kWh 1918 kWh £1,543 £192 £1,735 £21,242 12.2 yrs £13,462
8 kW 8769 kWh 6577 kWh 2192 kWh £1,764 £219 £1,983 £23,276 11.7 yrs £16,386

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

13.5 kWh battery 5 kW example → Annual benefit: £1,258, Upfront: £19,623, Break-even: 15.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2192 kWh 1688 kWh 504 kWh £453 £50 £503 £13,519 26.9 yrs £-3,456
3 kW 3288 kWh 2532 kWh 756 kWh £679 £76 £755 £15,554 20.6 yrs £-459
4 kW 4384 kWh 3376 kWh 1008 kWh £905 £101 £1,006 £17,588 17.5 yrs £2,538
5 kW 5481 kWh 4220 kWh 1261 kWh £1,132 £126 £1,258 £19,623 15.6 yrs £5,535
6 kW 6577 kWh 5064 kWh 1513 kWh £1,358 £151 £1,509 £21,657 14.3 yrs £8,532
7 kW 7673 kWh 5908 kWh 1765 kWh £1,585 £176 £1,761 £23,692 13.5 yrs £11,529
8 kW 8769 kWh 6752 kWh 2017 kWh £1,811 £202 £2,013 £25,726 12.8 yrs £14,526

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

Figures are illustrative and use the same method as the calculator above. For exact results, adjust your roof direction, tariff, and usage in the calculator.

Insights for TR24

Figures below are tailored to TR24 — click through for full league tables.

Big-Roof Britain Rank #746 of 2182
5.3 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #77 of 2997
9.6 years (UK avg 11.3 years)
~£1,055 /yr • £10,173 upfront
Standing-Charge Drag Rank #1204 of 2997
18.7% (UK avg 21.7%) drag on savings
£197 fixed • ~£1,055 /yr value

Your Area at a Glance

Your Electricity Rate
26.82p/kWh
Daily Fixed Charge
54.03p/day
Local Sunshine
1096kWh/kW
A 1 kW system generates ~1096 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
5.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 64% • Flats: 6% • Bungalows: 30% Based on 184 properties

Coverage

Isles of Scilly (100%)

Areas Covered

Tresco

Data Sources & Assumptions

Solar yield: PVGIS (EU Joint Research Centre), January 2025 data

Electricity rates: Ofgem price cap, Q4 2025

Installation costs: MCS certified installer data, March 2025

Property data: EPC open data (Open Government Licence), aggregated

All estimates are typical values. Actual results vary based on your specific situation, roof characteristics, and usage patterns.

Compare nearby areas

Nearby in Southern Western

TR23 (Isles of Scilly)
≈1.1 km away
Local sunshine: ~1,101 kWh/kWp · +0% vs TR24
TR25 (Isles of Scilly)
≈3.5 km away
Local sunshine: ~1,092 kWh/kWp · -0% vs TR24
TR21 (Isles of Scilly)
≈5.0 km away
Local sunshine: ~1,066 kWh/kWp · -3% vs TR24
TR22 (Isles of Scilly)
≈7.0 km away
Local sunshine: ~1,099 kWh/kWp · +0% vs TR24
TR19 (Cornwall)
≈51.0 km away
Local sunshine: ~1,083 kWh/kWp · -1% vs TR24
TR18 (Cornwall)
≈59.8 km away
Local sunshine: ~1,066 kWh/kWp · -3% vs TR24

Similar sunshine across the UK

PO11 (Havant)
~1,096 kWh/kWp · -0% vs TR24
PO9 (Havant)
~1,096 kWh/kWp · -0% vs TR24
PO2 (Portsmouth)
~1,096 kWh/kWp · -0% vs TR24