Key takeaways
- Budget £4,800–£8,000 for a typical 4–6 kWp system without battery, £9,000–£15,000 with a 5–10 kWh battery.
- Mono PERC panels are the value choice; TopCon (n-type) panels are 2–4% more efficient at a 10–15% premium and worth it on small or shaded roofs.
- Hybrid inverters future-proof the install for battery and EV integration. Don't pay for a string inverter you'll have to replace in 3 years.
- Size to consumption + EV/heat-pump plans, not roof space. An oversized array on the wrong tariff is dead capital.
- Realistic payback in 2026 is 8–12 years for a self-consumption-optimised system, longer if export-heavy.
- The single biggest pitfall: undersized DC cabling and string design. Cheap installers skimp here, and you lose 5–8% generation forever.
What a solar PV install really involves
A residential solar PV install is four components: panels, inverter, isolators/protection, and (optionally) a battery. The panels generate DC electricity from sunlight. The inverter converts DC to AC and manages export to the grid. The isolators and DC/AC protection are safety kit required by MCS and DNO. The battery, if present, stores excess generation for use later.
The conversation that gets skipped most often is what the system is for. There are three meaningfully different objectives, and the right hardware differs for each:
- Maximum self-consumption — sized to match your daytime demand, modest battery, prioritises offsetting expensive imported electricity.
- Maximum export — sized to maximum roof capacity, no battery, banks on Smart Export Guarantee (SEG) rates.
- Whole-system integration — sized to support a heat pump, EV, and home battery, with hybrid inverter and tariff arbitrage.
Most households should be doing 1 or 3. Pure export-led setups rarely make sense in 2026 because SEG rates have dropped and self-consumed kWh save you 28–32p whereas exported kWh earn 5–15p. The maths heavily favours self-consumption.
Panel types: mono PERC vs TopCon vs the rest
The panel market in 2026 is dominated by two technology generations:
| Technology | Typical efficiency | Cost premium | Best for | Examples |
|---|---|---|---|---|
| Mono PERC (p-type) | 20–22% | Baseline | Standard installs with adequate roof | JA Solar, Trina Vertex S, Longi Hi-MO |
| TopCon (n-type) | 22–23.5% | +10–15% | Small/partial-shade roofs | Longi Hi-MO X6, Trina Vertex S+, JinkoSolar Tiger Neo |
| Heterojunction (HJT) | 22.5–24% | +25–35% | Premium installs, high-temperature locations | REC Alpha Pure, Meyer Burger |
| Polycrystalline | 16–18% | -15% | Avoid in 2026 — outdated tech | (Largely discontinued) |
The honest signal: mono PERC is the value sweet spot for most installs. TopCon makes sense when roof space is tight (every percent of efficiency matters) or when the array is partially shaded (TopCon's better low-light performance is worth the premium). Heterojunction is overkill for most UK domestic installs unless you're trying to maximise output from a constrained roof.
What actually matters more than the cell technology: the manufacturer's warranty and bankability. A 25-year linear power warranty from a Tier 1 manufacturer (JA Solar, Longi, Trina, JinkoSolar, REC, LG — though LG exited residential in 2022) is meaningful. A 25-year warranty from a brand you've never heard of and that may not exist in 2030 is not.
Inverter selection: string vs micro vs hybrid
The inverter is the brain of the system. Three architectures exist:
| Inverter type | Cost (4 kWp install) | Best for | Trade-offs |
|---|---|---|---|
| String inverter | £600–£1,200 | Simple unshaded roof, single string | One shaded panel drops the whole string. Poor partial-shade performance. |
| Hybrid inverter | £1,200–£2,400 | Almost all 2026 installs — battery-ready | Higher upfront cost, but no replacement needed when adding battery later. |
| Microinverters | £1,800–£3,000 | Complex roof, multiple orientations, partial shade | One per panel — more failure points but per-panel optimisation. |
| Power optimisers + string | £1,000–£1,800 | Mid-complexity roof | Hybrid solution. SolarEdge is the dominant player. |
The single most important inverter decision in 2026: buy a hybrid inverter even if you're not installing a battery yet. A hybrid inverter has an integrated battery management system and can take a battery later with minimal additional cost. A string inverter cannot — you'll either have to add an AC-coupled battery (less efficient, more expensive) or replace the whole inverter when the time comes. The £400–£800 hybrid premium pays back the first time you add a battery.
Brands worth considering in 2026: GivEnergy (UK-designed, strong support), SolaX, Solis, Sungrow, Fronius (premium), SolarEdge (premium with optimisers), Tesla (only if you're committing to the Powerwall ecosystem), Enphase (microinverter ecosystem).
Sizing: kW for the roof and kWh for the use
Sizing solar is the question that gets answered laziest. The right method has three steps.
Step 1: Annual generation potential
A 1 kWp south-facing array in the UK generates roughly 850–1,000 kWh/year, depending on location (Cornwall ~1,000, Inverness ~750). East/west orientations lose 15–20%; north-facing roofs lose 35–45% and rarely justify the install cost.
Step 2: Your annual consumption profile
The average UK household uses 2,700–3,500 kWh/year of electricity. Add 4,000–5,000 kWh if you have an EV charged at home; add 2,500–4,000 kWh if you have a heat pump. So a household running a heat pump and an EV might consume 10,000–13,000 kWh/year of electricity total.
Step 3: The self-consumption fraction
Without a battery, typical self-consumption is 30–45% — most generation happens midday when you're at work, and most consumption is evening and morning. With a 5 kWh battery, self-consumption rises to 55–70%. With a 10 kWh battery, 70–85%.
Putting it together: a 5 kWp array generates ~4,500 kWh/year. Without battery, 35% used (1,575 kWh saved at 30p = £472), 65% exported (2,925 kWh at 8p SEG = £234). Annual benefit £706. With a 5 kWh battery, 65% used (2,925 kWh × 30p = £878), 35% exported (1,575 kWh × 8p = £126). Annual benefit £1,004 — but the battery costs an extra £3,000–£4,500.
Cost breakdown: 2026 UK install pricing
| System | Typical 2026 cost | Annual saving (no EV/HP) | Payback |
|---|---|---|---|
| 3 kWp, no battery | £3,800–£4,800 | £420–£550 | 8–11 years |
| 4 kWp, no battery | £4,800–£6,000 | £570–£720 | 8–10 years |
| 6 kWp, no battery | £6,500–£8,000 | £800–£1,000 | 8–10 years |
| 4 kWp + 5 kWh battery | £8,500–£11,000 | £900–£1,150 | 9–12 years |
| 6 kWp + 10 kWh battery | £12,000–£15,500 | £1,400–£1,800 | 9–11 years |
| 10 kWp + 15 kWh + EV/HP | £18,000–£23,000 | £2,400–£3,200 | 7–10 years |
The pattern: payback is broadly similar across system sizes (8–11 years for sensibly specified systems). The marginal economics improve with EV and heat pump because more of the generation displaces expensive imported electricity at peak rates.
SEG (Smart Export Guarantee) tariffs in 2026
The Smart Export Guarantee replaced the Feed-in Tariff in 2020. All licensed energy suppliers must offer an export tariff; the rate is unregulated. In 2026 the landscape:
| Supplier | SEG rate | Notes |
|---|---|---|
| Octopus Outgoing | 15p (flat) or Agile (variable, often higher) | Best general rate |
| Tesla Energy Plan | 11p (Powerwall owners only) | Bundled with Tesla hardware |
| OVO | 4–7p | Lower; tied to OVO import tariff |
| E.ON Next Export | 5p–7.5p | Mid-tier |
| British Gas Export | 6.4p | Mid-tier |
| EDF Energy | 3p | Among the lowest |
You don't have to take your SEG from the same supplier as your import. Switching to Octopus Outgoing while remaining on a different import supplier is allowed and often makes sense. The Outgoing Agile tariff (variable, settled half-hourly) regularly pays 20–30p/kWh for export during peak grid stress hours, but requires smart export functionality from your inverter and a willingness to time-shift consumption.
MCS, DNO, and the install paperwork
Three regulatory hurdles:
- MCS accreditation — your installer must be MCS-certified, the install certificate is what energy suppliers require to register you for SEG.
- DNO notification — the Distribution Network Operator must be notified of any grid-connected generation. For systems under 3.68 kWp inverter capacity, this is a notification (G98). For systems above that, an application (G99) is required, can take 3–8 weeks, and may result in DNO requiring export limitation.
- Building Regulations — handled by the installer through the MCS scheme.
Common pitfall: G99 timing. If you live in an area with a constrained network (parts of London, the South West, rural Scotland), the DNO may delay or restrict approval. Get the DNO application in early and don't commit to install dates until G99 is confirmed.
Battery sizing: the right answer is rarely the obvious one
Battery sizing is a function of three things: solar generation, evening consumption, and tariff arbitrage potential.
- 5 kWh — covers typical 4–6 kWh evening consumption for a 3-bed semi without EV/heat pump. Sweet spot for most homes.
- 10 kWh — covers higher evening consumption or enables tariff arbitrage (charge cheap overnight, discharge in peak hours). Right size for households with EV or heat pump.
- 15+ kWh — tariff arbitrage and energy independence. Pays back faster on Octopus Flux or similar dynamic tariffs.
The mistake to avoid: oversizing the battery beyond your daily consumption. A 20 kWh battery in a house consuming 8 kWh/day spends most of its life partially charged and never pays back the extra capacity. Match the battery to the use case.
Common pitfalls
- Undersized DC cabling — losses 3–8% of generation forever. Inspect the spec; cables should be 4mm² or 6mm² for typical residential.
- Inverter sized to peak panel rating, not real-world output — UK panels rarely output STC values. A 5 kWp array does fine on a 4 kW inverter (the overhead clips at noon on the 10 best days of the year). Oversizing the inverter is wasted money.
- String design that combines panels of different orientations — destroys output. Each orientation needs its own string or microinverters.
- Cheap mounting hardware — fails before the panels do. Spec proper aluminium rails, stainless fasteners, and roof hooks rated for your roof type.
- "Include" panels that aren't actually MCS-listed — disqualifies the install from SEG. Always ask for the MCS certificate after install.
- Shading not assessed properly — a tree, chimney, or aerial can knock 20%+ off output. Insist on a shading survey.
- Battery brand-locked to inverter — limits future upgrade options. Where possible, pick an inverter that supports multiple battery brands.
FAQ
Q: How long do solar panels last?
A: Modern panels carry 25-year linear power warranties — typically guaranteeing 80–85% of nameplate output after 25 years. Real-world degradation is roughly 0.5%/year, so a panel installed in 2026 should still produce 87% of its rated output in 2050. Inverters have 5–10-year warranties and typically need replacement at 10–15 years (£800–£1,800 for a hybrid inverter swap).
Q: Will solar panels work in cloudy UK weather?
A: Yes. Solar panels generate diffuse light as well as direct sunlight, so a cloudy day still produces 15–35% of clear-sky output. The UK's annual insolation (850–1,000 kWh/kWp/year) is lower than southern Europe but high enough for solar to make economic sense in every region except parts of the far north of Scotland.
Q: Do I need permission to install solar?
A: For most homes, solar PV is permitted development — no planning permission needed. Exceptions: listed buildings, conservation areas (where you'll need planning consent), and installs that protrude more than 200mm from the roof surface. The DNO notification (G98/G99) is separate and always required.
Q: Should I lease solar panels or buy outright?
A: Buy outright if you can. Lease/rent-a-roof schemes (where a third party installs panels and you take a share of the savings) almost always have worse economics than ownership and can complicate selling the house. The exception is if you genuinely cannot raise the capital — but at 8–11 year payback, ownership is by far the better deal.
Q: How does cold weather affect output?
A: Counter-intuitively, panels work better at cold temperatures (silicon cells are more efficient when cool). The reason UK winter output is low is short days and low sun angles, not temperature. A clear cold winter day can produce strong output even at 0°C.
Q: What happens during a power cut?
A: A standard grid-tied solar system shuts off during a power cut for safety reasons (anti-islanding protection). To run during outages, you need a battery with backup capability (sometimes called "EPS" — Emergency Power Supply). Tesla Powerwall, GivEnergy, and Sigenergy all offer this; expect to pay £500–£1,500 extra for the backup-ready hardware.
Q: Is VAT charged on solar installations?
A: 0% VAT on residential solar PV, batteries, and heat pumps applies in the UK until at least March 2027. Check the quote includes 0% VAT — some installers still apply 20% by mistake or to opaque sub-components.
If you'd like to size a solar PV system for your specific roof, factor in your tariff and EV/heat pump plans, and model realistic payback, the solar sizing calculator on Eco Saving Hub does it interactively. Run your numbers at ecosavinghub.co.uk/solar-pv-battery-roi/ — it accounts for your roof orientation, shading, consumption pattern, and tariff to produce a realistic payback rather than a brochure number.
Want to model your specific home? Use our free ROI calculators →