Every few months a headline or a neighbour’s WhatsApp message revives the same dream: cover the roof in solar panels, add a battery, and never pay an energy bill again. It’s an appealing idea, and in sunnier, more consistent climates it’s closer to realistic than you might think. In the UK, the honest answer is more complicated. Solar and battery storage can dramatically cut what you draw from the grid, and for a growing number of homes it can get close to “mostly self-sufficient” for large parts of the year. But fully generating and storing all your own electricity, with no grid connection at all, is a genuinely different proposition from the grid-tied solar-plus-battery systems most installers quote for.
This article sets out the real numbers: how much a typical UK solar system produces, how that compares to what a typical household actually uses, why British winters make “full independence” much harder than people expect, what a home battery can and can’t cover, and what it actually takes - in equipment and cost - to go properly off-grid. We’ll also look at the practical alternative that most UK solar households end up using instead.
What a typical UK solar system actually produces
Start with consumption. Ofgem publishes Typical Domestic Consumption Values (TDCVs), the reference figures used across the industry for bills, quotes and price cap calculations. For electricity, the current bands are:
- Low usage (flats or one-bed homes, 1-2 people): 1,800 kWh per year
- Medium usage (2-3 bedroom homes, 2-3 people): 2,700 kWh per year
- High usage (4+ bedroom homes, 4-5 people): 4,100 kWh per year
Now the generation side. The average UK domestic solar PV system installed in 2024 was 4.6 kWp. Using a typical UK solar yield benchmark of roughly 900 kWh of generation per kWp of installed capacity per year (a figure for a well-sited, south-facing, unshaded roof near the geographic centre of the UK), that average 4.6 kWp system generates in the region of 4,140 kWh over a full year.
Put those two numbers side by side and the picture looks encouraging: a typical solar installation produces roughly enough electricity, annually, to cover a medium-use household’s entire electricity consumption, with some to spare. This is the number that gets quoted in marketing materials, and it isn’t wrong - as an annual total. The problem is that “annual total” is doing a lot of work to disguise what actually happens month to month, which is the part that determines whether you can genuinely disconnect from the grid rather than just offset your bill.
If you’re weighing up system size for your own roof, it’s worth getting a proper site-specific yield estimate rather than relying on national averages - orientation, pitch, shading and postcode all move the number meaningfully. Our solar page covers how installers size a system to your roof and usage rather than to a generic average.
The real obstacle: British winters don’t cooperate
This is the crux of why “fully off-grid” is a much harder proposition in the UK than in, say, southern Spain or California. Solar generation in the UK is heavily skewed towards the summer half of the year, and the swing between seasons is dramatic.
On a typical 6 kWp system, daily output runs to around 25 kWh on a good day in May or July. In December, the same system produces around 4.9 kWh a day - roughly an 80% reduction. Averaged across the year, winter months (broadly November to February) account for around 11% of a system’s total annual output, while the summer months (broadly May to August) account for around 38%. In other words, more than three times as much electricity gets generated in the four brightest months as in the four darkest ones.
The reasons are straightforward physics rather than anything installers can design around: roughly three times less daylight in December than in June, the sun sitting much lower in the sky (reducing the angle of incidence on most roofs), and heavier average cloud cover through winter. None of this is a fault in the panels or the installation - it’s simply what solar generation looks like at UK latitudes.
This is precisely why the “annual total covers annual usage” framing is misleading if your goal is genuine independence. A system that generates 4,140 kWh across the year might produce the bulk of that between April and September, while producing only a small fraction of what the same household needs to run lights, appliances, and - increasingly - heating and hot water, through the darkest, coldest months, which is exactly when electricity demand tends to be highest. Annual totals balance out on paper. Days and weeks in January do not.
What a home battery can - and can’t - fix
This is where batteries come in, and where a lot of the “go off-grid” marketing gets ahead of itself. A home battery doesn’t generate anything; it stores surplus solar generated during daylight hours so you can use it later - typically in the evening, overnight, or in the early morning before the sun is back up. That’s a genuinely useful and well-proven use case.
A Tesla Powerwall 3, one of the most common domestic units on the UK market, has 13.5 kWh of usable capacity. For a household using roughly 12 kWh a day, that’s approximately one day’s worth of storage from a single unit; two units get you to roughly two days. That’s enough to shift a sunny afternoon’s surplus into a normal evening and overnight period, which is exactly the pattern most home battery buyers are trying to solve - reducing what you draw from the grid at peak-rate times, and using more of the power your own roof already produced.
What a battery of this size categorically cannot do is bridge the multi-day (or multi-week) stretches of low generation that are routine in a UK winter. If your solar array is producing 4-5 kWh a day in December and your household is using 12-15 kWh a day for the same period - heating aside - a battery sized for daily cycling isn’t going to carry you through a week of overcast December weather with no grid to fall back on. It will run flat, typically within a day or two, and then you’re relying entirely on whatever your panels manage to trickle in on a grey Tuesday. Scaling the battery up to cover those stretches is technically possible, but it moves the economics and the physical footprint into a very different category, which is the subject of the next section.
What genuine off-grid actually takes - and costs
“Off-grid” in the loose, aspirational sense that most homeowners mean it - solar plus a battery, topped up by the grid when needed - is really just a normal grid-tied system. Genuine off-grid means no grid connection at all: every kWh the household uses, in every season, has to come from what’s generated and stored on site, or from a backup generator.
To make that work reliably through a UK winter, the sizing changes substantially. Where a typical grid-tied home might need 10-15 panels sized around summer generation and annual averages, a system genuinely designed for winter resilience without grid support can require 50-70 panels - often more than a typical roof can hold, pushing the array onto a ground-mounted frame instead. Battery capacity has to scale similarly: rather than the 10-15 kWh batteries common in grid-tied installations, off-grid setups are typically specified at somewhere between 15 and 36 kWh of usable storage, specifically so the household can coast through several consecutive low-generation days. And because even an oversized array and a large battery bank can still be caught out by an extended run of dark, still winter weather, most genuine UK off-grid installations also include a backup generator - adding fuel costs, maintenance, noise, and a reliance on liquid fuel that rather undercuts the “clean and silent” appeal of the original idea.
On cost: a standard 4 kW grid-tied solar installation in the UK typically runs to around £6,000-£8,000. Add battery storage and the combined cost rises further - a 5 kWh battery typically costs £3,000-4,000 installed, a 10 kWh battery £4,000-6,000, and a 15 kWh battery £5,000-7,000, putting a fairly standard grid-tied solar-plus-battery system in the region of £10,000-£15,000 all in. A genuine off-grid system needs an array several times larger than the standard 4 kW example above, a battery bank well beyond the 15 kWh bracket (often into the 24-36 kWh range), plus a generator and the additional installation complexity of a system with no grid safety net - all of which sit well outside the pricing brackets that apply to a normal grid-tied installation. It is, unambiguously, a much larger investment than the solar-plus-battery systems most UK installers are quoting for day to day.
The middle ground almost everyone actually uses: export what you don’t need, import what you do
Given all of the above, it’s worth being clear about what most UK solar households actually do, because it isn’t off-grid and it isn’t purely “sell everything back to the grid” either - it’s a hybrid that uses the grid as a very large, very reliable, no-maintenance battery.
The mechanism that makes this financially sensible is the Smart Export Guarantee (SEG), introduced on 1 January 2020. Under the SEG, electricity suppliers with 150,000 or more domestic customers are required to offer a tariff that pays generators for electricity exported to the grid - the rate must always be above zero, though beyond that suppliers set their own terms. In practice, SEG rates vary widely: from around 1-3p per kWh on basic no-strings tariffs up to 15-25p per kWh on tariffs that require switching supplier or installing through a particular provider, with households on export tariffs earning 13p per kWh on average in 2024-25.
The logic is simple and, unlike full off-grid, doesn’t require oversized equipment: on a bright June afternoon, a typical solar system generates more than the house is using. Rather than that surplus needing to be stored (which requires battery capacity you’d only use a few months a year) or wasted, it’s exported and paid for. In December, when the same system is producing a fraction of what the house needs, electricity is imported from the grid as normal. The household isn’t trying to be self-sufficient every single day - it’s optimising for the lowest net cost and, usually, a meaningfully reduced carbon footprint, while keeping the reliability of a grid connection as backup.
This is also the point at which sequencing matters if you’re planning more than one retrofit measure. Adding a heat pump changes your electricity consumption profile substantially - and doing that alongside, or shortly after, a solar and battery installation changes the sizing calculations for all of it. If you’re weighing up which to do first, our guide to sequencing solar and heat pump installations goes through how to plan the order so you’re not paying twice to resize a system you already installed.
So when does off-grid actually make sense?
None of this means off-grid never makes sense in the UK - it means it makes sense in a narrower set of circumstances than the marketing around “energy independence” implies. The clearest case is a genuinely remote property where a grid connection itself is expensive or impractical to install in the first place. UK grid connection costs vary hugely by circumstance: the average price of a new electricity supply connection is around £1,619, but costs range from roughly £450 up to £10,140 or more for difficult rural sites - for example, where a distribution network operator needs to carry out a lengthy road dig (a 60-metre dig alone was cited as pushing one connection cost up to that £10,140 figure). For a remote self-build, a barn conversion far from the nearest pole, or a plot where the connection quote comes back eye-wateringly high, a well-specified off-grid system (oversized array, larger battery bank, generator backup) can start to look like the more sensible investment when weighed against that connection cost, rather than against a grid connection that’s already sitting there ready to use.
For the overwhelming majority of UK homes, though, the grid connection already exists, it’s already paid for, and it works reliably through every winter without needing a generator, a much bigger roof, or a battery bank sized for the worst week of the year rather than a normal one. In that situation, going properly off-grid means paying substantially more to replicate - imperfectly, and at real ongoing cost and maintenance - something you already have. The financially and practically sound approach for the vast majority of self-funded retrofits is the one described above: size solar and battery storage sensibly around your actual usage and roof, use the Smart Export Guarantee to get paid for summer surplus, and let the grid do what it’s good at during the months when your own generation can’t keep up.
If you’re weighing up solar, a battery, or a heat pump for your own home, the right starting point isn’t a nationwide average - it’s a proper assessment of your roof, your usage, and your property’s current energy performance. That’s the information a specialist needs to size a system that actually matches how your household uses electricity, rather than an off-the-shelf number pulled from a marketing page.
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