One peak sun hour = 1 kWh/m² of solar energy. A 4 kWp system with 2.5 peak sun hours/day generates approximately 4 × 2.5 × 365 × 0.80 = 2,920 kWh/year. Values below are annual averages from NASA POWER (ALLSKY_SFC_SW_DWN — all-sky conditions). Use the calculator above for your exact postcode.
* 4kWp system, PR 0.80, £0.26/kWh, 100% self-consumption. Source: NASA POWER ALLSKY_SFC_SW_DWN.
Plug-in balcony solar lets renters and flat dwellers generate electricity without roof access. The government's Solar Roadmap (June 2025) committed to a safety review of sub-800W plug-in systems. Legalisation of certified inverter systems expected 2026. The 57% of UK residents without roof access represents 8–12 million households.
0% VAT on solar installations until April 2027 makes the economics compelling today.
UK irradiance (2.2–3.2 peak sun hours/day) is comparable to Germany — the barrier is regulatory, not climatic. Germany has 435,000+ Balkonkraftwerk systems. The USA permits plug-in solar under NEC Article 705 across most states.
| Factor | 🇬🇧 UK | 🇺🇸 USA | 🇩🇪 Germany |
|---|---|---|---|
| Plug-in legal? | 2026 expected | Most states: Yes | Yes (800W) |
| Max size | 800W (planned) | Up to 2kW | 800W AC |
| Market size | Pre-commercial | 1–3M est. | 435k+ systems |
| Peak sun hrs/day | 2.4–3.2 | 3.5–7.5 | 2.5–3.5 |
| Electricity price | £0.26/kWh | $0.14–0.28 | €0.32/kWh |
| Typical payback | 3–6 years | 4–8 years | 3–5 years |
| Gov. scheme | SEG + 0% VAT | 30% Federal ITC | Feed-in tariff |
The global balcony solar (plug-in PV / Balkonsolar) market grew to an estimated £3–4 billion annual market in 2024, driven by Germany (435,000+ registered systems), the Netherlands, Austria, and Switzerland. In Germany the category is known as Balkonkraftwerk — typically €350–700 for a complete 600–800W kit. The US market is large and largely untracked; estimates suggest 1–3 million small residential systems deployed. The UK balcony solar market is pre-commercial for plug-in systems, with an active community of 20,000–50,000 early adopters on Reddit r/SolarUK and MoneySavingExpert. The Renters' Rights Act 2025 prevents landlords unreasonably refusing energy improvements, further strengthening the UK addressable market.
The best time of year to install solar panels in the UK is autumn and winter (October–February). December and January together account for only 8% of annual output — you lose almost nothing by installing in winter, but gain competitive quotes, faster slots, and panels ready for the spring surge. Avoid June–August when 12+ week wait times are common.
March–May: good choice. Generation ramps fast. Installers busy but manageable. Good combo of speed and immediate return.
Worst time. Peak demand, least competitive quotes, 6–12+ week wait lists. You miss peak generation while queuing.
Best time. Oct–Nov: demand falls sharply, quotes 10–15% lower, slots available within days. System ready for spring.
Also excellent. Dec–Feb: lowest competition, best prices, fastest slots. Only 8% of annual generation in these two months combined.
| Month | Avg Daily Output (4kWp, South England) | % of Annual | Installer Demand | Quote Competition | Verdict |
|---|---|---|---|---|---|
| January | 5.6 kWh/day | 4.4% | Very Low | Best prices | ✅ Ideal install month |
| February | 7.8 kWh/day | 6.1% | Low | Excellent | ✅ Ideal install month |
| March | 11.4 kWh/day | 9.0% | Growing | Good | ✅ Good — beat the rush |
| April | 14.8 kWh/day | 11.7% | High | Fair | ⚠ Getting busy |
| May | 16.2 kWh/day | 12.8% | Very High | Competitive | ⚠ Expect delays |
| June | 16.8 kWh/day | 13.3% | Peak | Worst | ❌ Avoid if possible |
| July | 16.4 kWh/day | 12.9% | Peak | Worst | ❌ Avoid — 6–12wk wait |
| August | 14.9 kWh/day | 11.8% | Very High | Poor | ⚠ Still very busy |
| September | 11.6 kWh/day | 9.1% | Easing | Improving | ✅ Getting better |
| October | 7.9 kWh/day | 6.2% | Low | Good | ✅ Great timing |
| November | 5.4 kWh/day | 4.3% | Very Low | Excellent | ✅ Ideal — ready for spring |
| December | 4.6 kWh/day | 3.6% | Lowest | Best prices | ✅ Ideal install month |
A standard UK rooftop installation is 4–6 kWp (10–16 × 400W panels). 4kWp is most common, generating 2,800–4,200 kWh/year depending on location.
A fully installed 4kWp rooftop system costs £6,000–£9,000 in 2025 including 0% VAT. Adding a 10kWh battery adds approximately £4,000–£7,000.
Payback: 7 years (south England, high self-consumption) to 12 years (north Scotland). Smart Export Guarantee (SEG) tariff shortens payback by 1–2 years.
Annual savings from a 4kWp system: £300 (north Scotland, low self-consumption) to £900+ (south England, battery). National average ~£550–700/year.
Modern panels are guaranteed 25 years (~80% output at year 25). Inverters need replacing after 10–15 years (£500–£1,500). Then 13–18 years of free electricity.
UK homes with solar sold for approximately 6.9% more than comparable properties without solar in 2025. Solar also improves EPC ratings.
0% VAT on supply and installation until 31 March 2027. Smart Export Guarantee (SEG) pays for surplus exported. ECO4 offers up to 100% funding for qualifying households.
South-facing (180°) gives maximum output. SE and SW give ~8–12% less. East and west give 15–25% less. North-facing not recommended. Optimal tilt: 30–35°.
Great Britain's solar data hub — live national generation, postcode solar calculators via NASA POWER satellite data, peak sun hours for every UK city and region, balcony solar guidance, installation timing advice, and the definitive UK solar record tracker. All data is open-source and free.
Great Britain broke four records in 25 days during April 2026, culminating in 15,158 MW on 23 April 2026 — 42% of the entire GB grid from solar alone. On 22 April, zero-carbon sources hit 98.8% of grid supply and gas fell to just 1.2%.
| Milestone | Value | Date |
|---|---|---|
| All-time peak | 15,158 MW | 23 Apr 2026 |
| 42% of GB grid at peak | 36.4 GW | 23 Apr 2026 |
| 98.8% zero-carbon grid | record low gas | 22 Apr 2026 |
| 3rd record (interim) | 14,400 MW | 7 Apr 2026 |
| 2nd record (interim) | 14,100 MW | 6 Apr 2026 |
| Previous all-time peak | 14,000 MW | 8 Jul 2025 |
| 2024 annual peak | 11,500 MW | 2 Jun 2024 |
| 2023 annual peak | 10,971 MW | 20 Apr 2023 |
| 2025 annual generation | 18,314 GWh | Full year |
| 2025 share of UK electricity | 6.3% | Full year |
| Installed capacity (2026) | ~20+ GW | Early 2026 |
| Govt 2030 target | 45–47 GW | Target 2030 |
Total deployed capacity exceeded 20 GW by early 2026. New homes require solar from 2027 under the Future Homes Standard. Cleve Hill (373 MW, Kent) is the UK's largest solar farm.
| Region / Type | Installed | Share |
|---|---|---|
| England (total) | ~18 GW | ~87% |
| Scotland | ~1.2 GW | ~6% |
| Wales | ~0.8 GW | ~4% |
| Large-scale (>1 MW) | ~14 GW | ~70% |
| Residential rooftop | ~4 GW | ~20% |
| Commercial rooftop | ~2 GW | ~10% |
| Cleve Hill (largest) | 373 MW | 1 site |
| New installs 2025 | ~250,000 | Record yr |