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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in CM3 (Chelmsford)

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

Solar Calculator

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
11.8 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,032
What you save every year
Profit Over 25 Years
£13,585
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 Eastern, the current unit rate is 26.53p/kWh with a 48.25p/day standing charge. Your postcode’s south-facing sunshine yield is 1035 kWh/kW — 26 above the regional median (1009).

Read the full story

A typical roof here lands around 6.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 1035 kWh per year on a south-facing roof. We value self-used electricity at 26.5p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.5p/kWh
Standing charge
48.2p/day
Sunshine yield (south)
1035 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: £860, Upfront: £10,173, Break-even: 11.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2070 kWh 828 kWh 1242 kWh £220 £124 £344 £4,069 11.8 yrs £2,809
3 kW 3105 kWh 1242 kWh 1863 kWh £330 £186 £516 £6,104 11.8 yrs £4,213
4 kW 4140 kWh 1656 kWh 2484 kWh £439 £248 £688 £8,138 11.8 yrs £5,618
5 kW 5175 kWh 2070 kWh 3105 kWh £549 £311 £860 £10,173 11.8 yrs £7,022
6 kW 6210 kWh 2484 kWh 3726 kWh £659 £373 £1,032 £12,207 11.8 yrs £8,426
7 kW 7245 kWh 2898 kWh 4347 kWh £769 £435 £1,204 £14,242 11.8 yrs £9,831
8 kW 8281 kWh 3312 kWh 4968 kWh £879 £497 £1,376 £16,276 11.8 yrs £11,235

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: £1,031, Upfront: £12,273, Break-even: 11.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2070 kWh 1242 kWh 828 kWh £330 £83 £412 £6,169 15.0 yrs £2,078
3 kW 3105 kWh 1863 kWh 1242 kWh £494 £124 £618 £8,204 13.3 yrs £4,166
4 kW 4140 kWh 2484 kWh 1656 kWh £659 £166 £825 £10,238 12.4 yrs £6,255
5 kW 5175 kWh 3105 kWh 2070 kWh £824 £207 £1,031 £12,273 11.9 yrs £8,344
6 kW 6210 kWh 3726 kWh 2484 kWh £989 £248 £1,237 £14,307 11.6 yrs £10,433
7 kW 7245 kWh 4347 kWh 2898 kWh £1,153 £290 £1,443 £16,342 11.3 yrs £12,522
8 kW 8281 kWh 4968 kWh 3312 kWh £1,318 £331 £1,649 £18,376 11.1 yrs £14,610

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: £1,116, Upfront: £13,673, Break-even: 12.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2070 kWh 1449 kWh 621 kWh £384 £62 £447 £7,569 16.9 yrs £1,362
3 kW 3105 kWh 2174 kWh 932 kWh £577 £93 £670 £9,604 14.3 yrs £3,793
4 kW 4140 kWh 2898 kWh 1242 kWh £769 £124 £893 £11,638 13.0 yrs £6,224
5 kW 5175 kWh 3623 kWh 1553 kWh £961 £155 £1,116 £13,673 12.2 yrs £8,655
6 kW 6210 kWh 4347 kWh 1863 kWh £1,153 £186 £1,340 £15,707 11.7 yrs £11,086
7 kW 7245 kWh 5072 kWh 2174 kWh £1,346 £217 £1,563 £17,742 11.4 yrs £13,517
8 kW 8281 kWh 5796 kWh 2484 kWh £1,538 £248 £1,786 £19,776 11.1 yrs £15,948

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: £1,142, Upfront: £15,423, Break-even: 13.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2070 kWh 1511 kWh 559 kWh £401 £56 £457 £9,319 20.4 yrs £-183
3 kW 3105 kWh 2267 kWh 838 kWh £601 £84 £685 £11,354 16.6 yrs £2,351
4 kW 4140 kWh 3022 kWh 1118 kWh £802 £112 £914 £13,388 14.7 yrs £4,885
5 kW 5175 kWh 3778 kWh 1397 kWh £1,002 £140 £1,142 £15,423 13.5 yrs £7,418
6 kW 6210 kWh 4534 kWh 1677 kWh £1,203 £168 £1,370 £17,457 12.7 yrs £9,952
7 kW 7245 kWh 5289 kWh 1956 kWh £1,403 £196 £1,599 £19,492 12.2 yrs £12,486
8 kW 8281 kWh 6045 kWh 2236 kWh £1,604 £224 £1,827 £21,526 11.8 yrs £15,019

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: £1,159, Upfront: £17,173, Break-even: 14.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2070 kWh 1553 kWh 518 kWh £412 £52 £464 £11,069 23.9 yrs £-1,796
3 kW 3105 kWh 2329 kWh 776 kWh £618 £78 £695 £13,104 18.8 yrs £806
4 kW 4140 kWh 3105 kWh 1035 kWh £824 £104 £927 £15,138 16.3 yrs £3,408
5 kW 5175 kWh 3882 kWh 1294 kWh £1,030 £129 £1,159 £17,173 14.8 yrs £6,010
6 kW 6210 kWh 4658 kWh 1553 kWh £1,236 £155 £1,391 £19,207 13.8 yrs £8,613
7 kW 7245 kWh 5434 kWh 1811 kWh £1,442 £181 £1,623 £21,242 13.1 yrs £11,215
8 kW 8281 kWh 6210 kWh 2070 kWh £1,648 £207 £1,855 £23,276 12.6 yrs £13,817

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: £1,176, Upfront: £19,623, Break-even: 16.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2070 kWh 1594 kWh 476 kWh £423 £48 £471 £13,519 28.7 yrs £-4,109
3 kW 3105 kWh 2391 kWh 714 kWh £634 £71 £706 £15,554 22.0 yrs £-1,438
4 kW 4140 kWh 3188 kWh 952 kWh £846 £95 £941 £17,588 18.7 yrs £1,232
5 kW 5175 kWh 3985 kWh 1190 kWh £1,057 £119 £1,176 £19,623 16.7 yrs £3,903
6 kW 6210 kWh 4782 kWh 1428 kWh £1,269 £143 £1,412 £21,657 15.3 yrs £6,573
7 kW 7245 kWh 5579 kWh 1666 kWh £1,480 £167 £1,647 £23,692 14.4 yrs £9,244
8 kW 8281 kWh 6376 kWh 1905 kWh £1,692 £190 £1,882 £25,726 13.7 yrs £11,914

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 CM3

Figures below are tailored to CM3 — click through for full league tables.

Big-Roof Britain Rank #435 of 2182
5.7 kWp (UK avg 5.1 kWp)
~12 panels (≈430 W)
Solar Payback Index Rank #310 of 2997
10.3 years (UK avg 11.3 years)
~£1,186 /yr • £12,207 upfront
Standing-Charge Drag Rank #213 of 2997
14.8% (UK avg 21.7%) drag on savings
£176 fixed • ~£1,186 /yr value

Your Area at a Glance

Your Electricity Rate
26.53p/kWh
Daily Fixed Charge
48.25p/day
Local Sunshine
1035kWh/kW
A 1 kW system generates ~1035 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
6.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 71% • Flats: 12% • Bungalows: 16% Based on 13,576 properties

Coverage

Chelmsford (68%)|Maldon (17%)|Braintree (14%)|Uttlesford (1%)

Areas Covered

South Woodham-Elmwood and Woodville, Little Baddow, Danbury and Sandon, Hatfield Peverel & Terling, Boreham and The Leighs, Broomfield and The Walthams, Althorne, Bicknacre and East and West Hanningfield + 5 more

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 Eastern

CM98 (Chelmsford)
≈6.5 km away
Local sunshine: ~1,036 kWh/kWp · +0% vs CM3
CM9 (Maldon)
≈6.9 km away
Local sunshine: ~1,054 kWh/kWp · +2% vs CM3
CM99 (Chelmsford)
≈6.9 km away
Local sunshine: ~1,039 kWh/kWp · +0% vs CM3
CM2 (Chelmsford)
≈7.7 km away
Local sunshine: ~1,033 kWh/kWp · -0% vs CM3
CM1 (Chelmsford)
≈8.6 km away
Local sunshine: ~1,033 kWh/kWp · -0% vs CM3
CM8 (Braintree)
≈10.4 km away
Local sunshine: ~1,050 kWh/kWp · +1% vs CM3

Similar sunshine across the UK

GU29 (Chichester)
~1,035 kWh/kWp · -0% vs CM3
LN13 (East Lindsey)
~1,035 kWh/kWp · +0% vs CM3
SO40 (New Forest)
~1,035 kWh/kWp · -0% vs CM3