Solar Panel Output by Month UK: The Full Table
How much do panels actually generate each month? A lot more in July than December — summer makes around four times the winter output. Here’s the full month-by-month table, scalable to any system size.
The short answer
A typical 4kW UK solar system generates around 3,400–4,000 kWh a year — but very unevenly across the months. In midwinter (December/January) it makes only ~90–120 kWh a month (~3 kWh a day); in peak summer (May–July) it climbs to ~450–500 kWh a month (~15–16 kWh a day). So the best months produce roughly four times the worst months. Winter (Nov–Feb) delivers just 12–17% of the annual total; summer (May–Aug) delivers 35–40%.
This seasonal swing is completely normal and predictable — solar is sized to cover a useful share of your annual electricity, with summer’s surplus compensating for winter’s lean months. The full month-by-month table is below, in both kWh per day and per month, plus a per-kWp version so you can scale it to any system size (just multiply by your kWp). And crucially: temperature isn’t the reason for the winter drop — it’s the short days and low sun. The table, the scaling, and what it means for your savings and battery, below.
What this guide covers
The headline “3,400 kWh a year” figure hides the most important thing about solar: when that electricity actually arrives. A system generates a flood of power in summer and a trickle in winter, and understanding that shape helps you set realistic expectations, size a battery sensibly, and not panic when December’s generation looks tiny. Here’s the honest month-by-month picture.
Solar panel output by month: the full table (4kW system)
Here’s the month-by-month output for a typical 4kW south-facing system in central England, based on PVGIS (the European Commission’s solar model), at a 35° roof pitch. Figures are approximate averages — your own will vary with location, roof and weather.
| Month | Output (kWh) | Per day (kWh) | Share of year |
|---|---|---|---|
| January | ~100 | ~3.2 | 3% |
| February | ~150 | ~5.4 | 4% |
| March | ~270 | ~8.7 | 7% |
| April | ~380 | ~12.7 | 10% |
| May | ~480 | ~15.5 | 13% |
| June | ~490 | ~16.3 | 13% |
| July | ~470 | ~15.2 | 12% |
| August | ~410 | ~13.2 | 11% |
| September | ~315 | ~10.5 | 8% |
| October | ~210 | ~6.8 | 6% |
| November | ~120 | ~4.0 | 3% |
| December | ~100 | ~3.2 | 3% |
| Year | ~3,500 | ~9.6 avg | 100% |
The pattern is unmistakable: May, June and July each produce nearly five times what December does. The four summer months (May–August) alone deliver around half the entire year’s generation, while the four darkest months (Nov–Feb) contribute barely 13% between them. This isn’t a flaw — it’s simply how UK solar works, and it’s exactly why systems are sized around the annual total rather than any single month.
Scale it to any system size (per kWp)
The table above is for a 4kW system, but the beauty of solar is that output scales almost linearly with size — so you can estimate any system easily. A well-sited south-facing UK system generates roughly 950–1,000 kWh per kWp per year, and the monthly shape is the same whatever the size. To find your own numbers, just multiply the 4kW figures by the ratio of your system size:
- 3kW system: multiply each figure by 0.75 (≈2,600 kWh/yr)
- 5kW system: multiply by 1.25 (≈4,375 kWh/yr)
- 6kW system: multiply by 1.5 (≈5,250 kWh/yr)
- 8kW system: multiply by 2.0 (≈7,000 kWh/yr)
So a 6kW system in June generates around 490 × 1.5 ≈ 735 kWh; a 3kW system in December around 100 × 0.75 ≈ 75 kWh. The per-kWp approach is how installers estimate systems, and it lets you sanity-check any quote against these seasonal norms.
Daily output through the year
One “daily output” number is misleading — think in seasonal bands
A 4kW system averages around 9–10 kWh per day across the whole year, but that single figure hides an enormous swing, so it’s far more useful to think in seasonal bands. In midsummer, a 4kW system produces roughly 15–17 kWh a day on average, with bright June days hitting 20 kWh or more. In spring and autumn, expect around 8–12 kWh a day. And in midwinter, it drops to just 3–4 kWh a day — with a dark, heavily overcast December day producing as little as 2 kWh. Individual days vary even within a month, because generation depends on daylight and cloud: a bright overcast day still yields perhaps 10–30% of a clear-sky day, while thick storm cloud cuts it to almost nothing. If you have a solar monitor, you’ll watch this play out in real time — the key is to judge your system over a month or a year, never on one gloomy day. To scale to your size: divide the daily figures by 4 for a per-kW number, then multiply by your kWp (a 6kW system averages ~14 kWh/day, a 5kW ~12 kWh/day).
Why solar output drops so much in winter
UK winter output falls to a fraction of summer’s for two reasons — and, surprisingly, cold isn’t one of them. First, shorter days: December offers only 7–8 hours of daylight versus 16–17 in June, so there’s far less time to generate. Second, the sun’s low angle: in winter the sun stays low, so its light travels through more atmosphere and hits the panels at a shallow angle — both of which reduce the energy reaching the cells. Together these mean winter (Nov–Feb) delivers only ~12–17% of annual output. What doesn’t cause the drop is cold — in fact, panels are slightly more efficient in cool temperatures, since heat marginally reduces their performance, so a crisp bright winter day generates well for the few hours it lasts. It’s the shortness of the day and the low sun, not the chill, that limit winter. This is why solar is sized around annual generation, and why — as the next section explains — a battery can’t rescue your winter by storing summer’s excess.
What the seasonal swing means for savings & battery
The four-to-one seasonal swing has two practical consequences worth understanding. Savings are uneven: because you generate ~4× more in summer, your bill savings follow the same shape. At ~25p a unit, a 4kW system might offset £110–£120 of your electricity bill in May but only £25–£30 in December — so winter bills won’t vanish the way summer ones can, and that’s normal; the annual saving (typically several hundred pounds) is what counts. A battery can’t move summer into winter: a common misconception is that storage banks your summer surplus for the dark months. It can’t — a home battery shifts power within a day (midday generation used in the evening), not across seasons. So size a battery around your daily surplus, not annual generation: in summer it fills easily and lifts your self-consumption from the 30–50% of a battery-less system to 70–80%; in winter there’s often too little surplus to fill it. Understanding your month-by-month output — not just the headline annual figure — is what lets you size a system and battery sensibly.
What changes your numbers
The table is a central-England, south-facing average — several factors will shift your actual output. Orientation is the biggest: a south-facing roof produces 100% of the potential, east or west around 75–80%, and north-facing only 50–60%. Location: southern England (especially the south coast) generates ~15–20% more than northern Scotland, mostly in winter — though interestingly the summer-to-winter swing is less extreme in the cloudier north and west, which rely more on consistent diffuse light. Roof pitch: 30–40° is close to ideal in the UK. Shading from chimneys, trees or buildings reduces output disproportionately (see our shading guide). And weather varies year to year, so treat any figure as a multi-year average, not a guarantee. For a genuinely accurate, location-specific estimate, the best free tool is PVGIS (the EU’s solar calculator) — enter your postcode, roof direction, angle and size, and it gives you a month-by-month estimate for your exact spot. It’s what installers, and this guide’s figures, are based on.
Frequently asked questions
How much do solar panels generate each month in the UK?
A 4kW system makes ~3,400–4,000 kWh/year, spread unevenly: ~100 kWh in December (~3/day) up to ~490 kWh in June (~16/day) — the best months make ~4× the worst. Roughly: Jan 100, Feb 150, Mar 270, Apr 380, May 480, Jun 490, Jul 470, Aug 410, Sep 315, Oct 210, Nov 120, Dec 100 kWh.
How many kWh per day?
A 4kW system averages ~9–10 kWh/day annually, but think in bands: ~15–17/day midsummer (20+ on bright June days), ~8–12/day spring/autumn, just ~3–4/day midwinter. Divide by 4 for per-kW, then multiply by your size (6kW ≈ 14/day).
Why is winter output so low?
Short days (7–8 hours vs 16–17 in June) and the sun’s low angle — not cold. Panels are actually slightly more efficient when cool. Winter (Nov–Feb) makes just 12–17% of the year; summer (May–Aug) 35–40%.
How do I calculate output for my system size?
Work per kWp (~950–1,000 kWh/kWp/year) and multiply. Scale the 4kW table by 0.75 (3kW), 1.25 (5kW), 1.5 (6kW) or 2.0 (8kW). For an exact figure, use PVGIS with your postcode, roof direction and angle.
What does the swing mean for savings and battery?
Savings are seasonal too — a 4kW system might save ~£115 in May but only ~£28 in December. A battery shifts power within a day, not across seasons, so size it for daily surplus, not annual generation. It boosts self-consumption to 70–80% in summer.
Do panels work on cloudy winter days?
Yes — they generate from daylight, not just sun, so cloudy days still produce (a bright overcast day ≈ 10–30% of clear-sky). Only thick storm cloud drops output near zero. Cloudier regions like Scotland actually have a less extreme summer-winter swing.
Summer floods, winter trickles — and that’s completely normal
The bottom line: A 4kW UK system generates ~3,400–4,000 kWh a year, but summer months (May–July, ~480 kWh each, ~15 kWh/day) produce around four times the winter months (Dec/Jan, ~100 kWh, ~3 kWh/day). Winter is low because of short days and a low sun — not cold. Scale the table by your system size (per kWp × your kWp), size any battery around daily not seasonal surplus, and don’t judge solar on a gloomy December: it’s the annual total, and the summer surplus that offsets winter, that make the savings add up.
Get my free quotes →The verdict
Understanding solar output by month turns a confusing single number (“3,400 kWh a year”) into a picture you can actually plan around. The shape is dramatic but entirely predictable: a summer flood, roughly four times the size of the winter trickle, with May, June and July doing the heavy lifting and December barely registering. Once you know that, the rest falls into place — you stop worrying about a quiet winter monitor, you size a battery around a summer day’s surplus rather than an impossible dream of storing July for January, and you judge your system on its annual total, exactly as it was designed to be.
The figures here are solid UK averages, but your roof is specific — its direction, pitch, location and shading all shift the numbers. The two ways to get your real month-by-month output are the free PVGIS tool (enter your postcode) or, better still, a proper installer’s assessment that models your actual roof. A couple of free, no-obligation quotes from MCS-certified installers will give you a generation estimate tailored to your home — month by month, season by season — so you know exactly what to expect before you commit.
Important
Going Solar UK is an introduction service, not an installer. This guide is general 2026 information: the monthly and daily output figures here are typical averages for a south-facing system in central England (based on PVGIS modelling) and are estimates, not guarantees – your actual output depends on your location, roof orientation and pitch, shading, system size, equipment and year-to-year weather. Always obtain a professional, location-specific estimate for your own property before making decisions.
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.