8kW Solar System: Cost, Output & Is It Right for You?
The big-house system for high-usage homes — one rung below 10kW. Here’s what an 8kW array costs in 2026, what it generates, and whether it beats a 10kW or a 6kW for your household.
The short answer
An 8kW solar system costs £9,000–£13,000 fully installed in 2026 and generates roughly 6,800kWh a year from 18–20 panels needing ~36–40m² of roof — usually across more than one roof face. It suits high-usage homes (5,000kWh+) — large households, EV owners, heat-pump homes — where it covers heavy demand and feeds a battery.
The key decision is 8kW vs 10kW vs 6kW: if you genuinely use 5,000kWh+ and have the roof, 8kW’s extra capacity costs proportionally less per kilowatt. Below that, a 5kW system pays back faster per pound. And whichever you pick, single-phase export limits shape the inverter design — we’ll cover that below. Full context sits in our solar panel sizes guide.
What this guide covers
The 8kW system is firmly in big-house territory: enough generation to run a heavily-electrified home — EV on the drive, heat pump humming, a household that actually uses power — and enough panels that roof space, not need, becomes the question. It sits one rung below the 10kW system and a clear step above the 5kW, and for the right high-usage household it’s often the sweet spot: most of 10kW’s generation, with slightly gentler roof and grid demands.
This guide gives you the honest 2026 numbers and settles the sizing question — because at this end of the ladder, buying too big is a real and expensive mistake. Let’s build up to it.
How much does an 8kW solar system cost in 2026?
| 8kW setup | Typical installed price (2026) | What you’re getting |
|---|---|---|
| Budget system | £9,000–£10,500 | Value panels, standard/export-limited inverter |
| Mid-range system | £10,500–£12,000 | Quality panels, hybrid (battery-ready) inverter |
| Premium / complex roof | £12,000–£13,000+ | Top-tier panels, optimisers, multi-face access |
| 8kW + 10kWh+ battery | £13,000–£19,000 | The high-usage family-home package |
That works out around £1,150–£1,600 per kilowatt — cheaper per watt than a 4kW or 5kW system, because fixed costs (scaffolding, the electrician’s day, DNO paperwork) spread across more panels. It’s roughly in line with a 10kW system’s per-kW rate. 0% VAT (to March 2027) is included; London and the South East run 15–25% higher. A hybrid inverter is almost always worth it at this size given how much a battery adds — the Solis hybrids are the value pick installers reach for. Across 18–20 panels, premium brands like Eurener or the top Tier 1 names add several hundred pounds.
18–20 panels — usually across multiple roof faces
At today’s 400–450W panels, 8kW means 18–20 panels across roughly 36–40m². That’s a lot of roof — on most homes it means using more than one face (front and back, or main roof plus a garage/extension), which brings orientation into play. The good news: mixed orientations aren’t a dealbreaker, and often help spread generation across the day. Our roof capacity guide shows how to measure your usable area, and it matters more at 8kW than any smaller size — this is where “will it even fit?” becomes the leading question.
Two roof realities worth knowing: east-west splits (panels on both slopes) work well at this size and flatten your generation curve, and where shading affects part of a large array, panel-level optimisers earn their keep by stopping one shaded face dragging down the rest.
What does an 8kW system generate?
| Scenario | Annual output | Daily average |
|---|---|---|
| South-facing, southern England | ~7,500kWh | ~20kWh |
| Average UK roof | ~6,800kWh | ~18–19kWh |
| East-west split or northern UK | ~5,800–6,400kWh | ~16–17kWh |
A bright summer day delivers 45–55kWh — enough to run the house, charge an EV and fill a battery with plenty to spare — while midwinter manages 5–8kWh. For calibration: the average UK home uses ~2,700–3,500kWh a year, so an 8kW system generates roughly double a typical household’s usage. That’s the crucial point about this size — it only makes financial sense if you genuinely consume a lot, because generation you can’t use or store exports at a low rate. On less ideal orientations the totals soften but the system still comfortably serves a high-usage home.
Savings and payback in 2026
At the 2026 price cap (~26p/kWh import, ~15p export), an 8kW system saves a high-usage home roughly:
- Self-consumption: using ~3,000–4,000kWh of your own generation directly saves £780–£1,040 a year.
- Export income: the remaining ~3,000–3,800kWh at typical SEG rates earns £450–£570 — more on the best export tariffs.
- Total: roughly £1,100–£1,600 a year, for payback around 7–10 years against panels warrantied 25+ years.
The decisive lever is self-consumption. An 8kW system generates so much that without high usage or a battery, a large share exports at 15p instead of displacing 26p imports — which quietly wrecks the payback. That’s why this size rewards EV homes, heat-pump homes and big households above all: they actually use the power. A battery is near-essential to make the most of it (below). If any support applies, our grants guide covers 2026’s real options — for most, the 0% VAT is the main help.
Battery pairing: 10kWh+ is the sweet spot
At 8kW, a battery isn’t a nice-to-have — it’s what stops your considerable midday surplus exporting cheaply and buying back expensively each evening. Our usual honesty holds (a battery rarely pays for itself on hardware alone), but at this generation level, paired with a smart tariff, it tips the household economics firmly positive.
Sizing: 10kWh+ suits most 8kW homes — enough to bank a real chunk of a summer day and cover the evening peak, with EV and heat-pump loads in mind. A 10kWh battery adds roughly £4,500–£6,500 installed; larger or stacked systems more. Modular ranges that expand (like the Fox ESS EP series) let you grow capacity as demand rises. Avoid discounted GivEnergy stock — post-administration, its warranties aren’t honoured, and on a big battery that’s a real risk. For the size-down option, our 5kWh battery guide covers smaller pairings.
Single-phase limits and G99 approval
This matters more at 8kW than any smaller size. Most UK homes have a single-phase supply, and exporting solar to the grid on single-phase is typically capped at 3.68kW without prior DNO approval. An 8kW system can exceed that, so installers handle it one of three ways: export limitation (the inverter caps grid export while you still use all you generate on-site), G99 DNO approval (pre-application to export more, adding a few weeks), or occasionally three-phase where available. None of this stops you having 8kW — it just shapes the inverter choice and timeline, and a good installer will advise based on your supply and whether you’re export-focused or self-consumption-focused. It’s the same inverter-sizing logic as any large system, just more pronounced. Expect a slightly longer lead time than a sub-4kW 4kW install that skips this step.
8kW vs 10kW vs 6kW: which is right?
| 5–6kW | 8kW | 10kW | |
|---|---|---|---|
| Typical cost installed | £7,000–£9,500 | £9,000–£13,000 | £10,000–£15,000 |
| Panels | 12–16 | 18–20 | 22–24 |
| Annual output | ~4,300–5,100kWh | ~6,800kWh | ~8,500kWh |
| Best for usage of | 3,500–5,000kWh | 5,000–7,000kWh | 7,000kWh+ |
| Roof needed | ~24–32m² | ~36–40m² | ~44–48m² |
| Single-phase export job? | Usually simple | Needs planning | Needs planning |
The honest rule at this end of the ladder: match the system to genuine usage, because oversizing is expensive here. If you use 5,000–7,000kWh — a big household, EV plus heat pump, someone home during the day — 8kW is the sweet spot, with most of 10kW’s generation and slightly easier roof and grid demands. Use 7,000kWh+ and have the roof? Step up to the 10kW system. Under ~5,000kWh, don’t buy 8kW to watch half of it export at 15p — a 5kW or 6kW system pays back faster per pound. Bigger isn’t better; best-matched is — the same principle we apply right across the sizes range.
8kW solar system: pros & cons
✓ Pros
- Ideal for large, high-usage & electrified homes
- ~6,800kWh/year — covers heavy demand + battery
- £1,100–£1,600 annual savings for the right home
- Cheaper per kW than 4–5kW systems
- Most of a 10kW’s output, slightly gentler demands
- Battery-ready with a hybrid inverter
✗ Cons
- Overkill below ~5,000kWh usage — surplus exports cheaply
- Needs 36–40m² — usually multiple roof faces
- £9k–£13k up front (£13k–£19k with battery)
- Single-phase export limits need planning / G99
- Nearly needs a battery to make full sense
Frequently asked questions
How much does an 8kW solar system cost in the UK?
£9,000–£13,000 fully installed in 2026, including panels, inverter, scaffolding, labour and 0% VAT. With a 10kWh+ battery, budget £13,000–£19,000. London and the South East add 15–25%.
How many panels, and will they fit?
18–20 modern panels across ~36–40m² — usually spanning more than one roof face, so 8kW suits larger detached homes or generous roof space. Check yours with our 2-minute roof guide.
How much electricity does it generate?
~6,800kWh a year on an average UK roof (18–19kWh/day), from 45–55kWh on peak summer days to 5–8kWh midwinter. South-facing southern arrays reach 7,500kWh+ — roughly double a typical home’s usage.
Is an 8kW system worth it?
For homes using 5,000kWh+ — big households, EVs, heat pumps — yes: it covers heavy demand and feeds a battery, at a lower per-kW cost than smaller systems. Below that usage, a 5kW system pays back faster per pound.
8kW or 10kW?
8kW for very high usage that still wants to stay manageable on single-phase; 10kW for the largest homes and biggest EV/heat-pump demand with the roof to match. Both need careful inverter sizing for the single-phase export limit.
Do I need three-phase power?
Not necessarily — 8kW runs on single-phase, but export is capped at 3.68kW without G99 DNO approval, or the system uses export limitation. Larger inverters or full export may need G99 or three-phase; your installer will advise.
The high-usage home’s sweet spot
The bottom line: For a genuinely high-usage, electrified home with the roof for it, 8kW is often the smartest big-system choice — most of a 10kW’s generation, cheaper per kW than smaller arrays, and gentler on your single-phase supply. Just don’t buy it for average usage.
Get my free quotes →The verdict
The 8kW system is the high-usage home’s sweet spot: most of a 10kW’s generation, a lower per-kilowatt cost than smaller arrays, and slightly gentler roof and grid demands. Paired with a battery and a smart tariff, for a big electrified household — EV, heat pump, the lot — it’s one of the strongest solar cases going.
But it lives or dies on genuine usage: generate double what you consume with nowhere to store it, and the surplus bleeds away at export rates. So size it honestly — compare survey-based quotes that model your roof and usage, and make the installer show their working across 6kW, 8kW and 10kW before you commit.
Important
Going Solar UK is an introduction service, not an installer. We don’t design, supply, or fit solar systems ourselves. Prices, outputs, savings and grid-rule details in this guide are indicative 2026 market averages and vary by property, region, network operator, roof, system design and tariff — always get a proper survey and quotes from MCS-certified installers before relying on them.
We may receive a commission when we introduce you to an installer, at no cost to you. Any contract for work is directly between you and the installer.