Small Solar Panels UK: Sizes, Uses and 12 V Systems from 5 to 200 W

Small solar panels of about 5 to 200 W charge 12 V batteries for sheds, garden lights, CCTV cameras, gates, electric fences, caravans and boats. By our PVGIS-based calculation, a 100 W panel tilted south near Manchester delivers about 350 Wh on an average June day and 80 Wh in December. Small panels cost more per watt than roof panels; off-grid systems need no DNO notice.

The second search term for this topic, small photovoltaic panel, describes the same thing: a module much smaller than the 400 to 460 W panels on house roofs, almost always built for 12 V battery charging rather than for feeding the grid. This guide sets out the sizes and weights from manufacturer data sheets, what a small panel yields in each part of Great Britain month by month, how to size a small off-grid system with real arithmetic and PVGIS battery simulations, and the wiring, fusing and mounting rules that keep it safe. It ends with the plug-in solar rules, which apply as soon as a panel feeds the house.

For panels that fold away for camping, see our guide to portable solar panels. For phone and car chargers, see our guide to solar chargers. For roof-size modules, see solar panel sizes in the UK.

What counts as a small solar panel

There is no formal definition. Retailers use “small” for panels from a few watts up to about 200 W. Above that, from about 300 W, begins the format used on roofs and in plug-in kits. What separates the two groups is less the size than the voltage each is designed for.

Most small panels have 36 cells in series, sometimes 30 or 39. That gives a voltage at maximum power of roughly 18 to 22 V and an open-circuit voltage of 20 to 25 V. It is the range a charge controller needs to charge a 12 V battery, which is why retailers call these 12 V panels even though they never deliver 12 V. Large roof panels, by contrast, run at 30 to 45 V and are built for inverters connected to the grid.

Small panels come in three constructions:

• Rigid glass panels in an aluminium frame. The standard for sheds, poles, walls and caravan roofs. Heaviest per watt, longest-lived.
• Flexible or semi-flexible panels. No glass or frame, bonded to curved boat and van roofs. Our guide to flexible solar panels covers their trade-offs.
• Small rigid boards for battery maintenance. A few watts in a plastic or aluminium frame, sold with clips for cars and motorcycles.

Sizes and weights from data sheets

The table brings together rigid glass panels from Victron’s data sheet, Renogy’s UK product pages and Ring’s specification sheet. Values are under standard test conditions: 1,000 W of sunlight per square metre at 25 °C. Power per square metre and weight per square metre are our calculations from the published dimensions.

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Three patterns stand out.

Weight follows area, not power. Every glass panel from 20 W upwards weighs 10.4 to 11.8 kg per square metre. Small panels are lighter because they are smaller, not because they are built differently. The tiny maintainer is heavier per square metre because its frame and junction box make up a larger share.

Small panels collect a little less per square metre. The best small panels here reach about 200 W per square metre, the older designs 160 to 190 W. A current roof panel of about 450 W on 1.76 by 1.13 metres reaches roughly 225 W per square metre. For the same power, a small panel needs somewhat more area.

Voltage stays near 20 V, current grows. From 20 W to 190 W the maximum power voltage barely moves, while the current rises from under 1 A to almost 9 A. That current decides the size of controller, cable and fuse.

The data sheets also differ on warranties. Victron gives 5 years on materials and workmanship, with 90 percent of power output guaranteed for 10 years and 80 percent for 25 years. Renogy’s 100 W panel carries a 10-year prorated materials and workmanship warranty; its 50 W panel lists a 5-year materials warranty and a 25-year output warranty.

How much a small panel yields in Great Britain

Yield depends on location, orientation, tilt, shade and season, not on the panel’s size, so the table works per 100 W. We ran PVGIS’s monthly radiation tool for 2005 to 2023 and applied a loss factor of 0.75, allowing 25 percent for heat, cabling, charge controller and battery losses. The loss factor is our assumption, consistent with our other off-grid guides; a PWM controller loses more, as explained below.

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The table holds the main lessons for planning:

• Winter is the design month. A panel tilted at 35 degrees collects a quarter or less of its June output in December. An off-grid system sized on the annual figure fails in winter.
• Steep beats shallow from October to February. At 60 degrees near Manchester, December output rises by a fifth against 35 degrees, at a cost of some summer output that a small system often cannot use anyway. A vertical panel on a south wall does as well as a 60-degree one in December.
• Flat panels suit summer only. A panel lying flat on a caravan or boat roof matches a tilted one in June but collects half as much or less in December.
• North and south differ less than expected over a year, more in winter. Edinburgh matches Manchester annually but falls about 20 percent behind in December at 35 degrees.

These are long-term averages. A clear June day can deliver half as much again; a week of low cloud in December can deliver almost nothing.

Off-grid basics: panel, controller, battery and loads

Most small panels work in a stand-alone system, not connected to the grid. The panel charges a battery, and the loads draw from the battery. Four parts make up the system:

• Panel. Delivers DC at 18 to 22 V at its maximum power point.
• Charge controller. Matches the panel to the battery and stops overcharging. A PWM controller ties the panel to battery voltage; Victron’s white paper calculates that at 25 °C this harvests 81 W from a 100 W panel where an MPPT controller harvests the full 100 W, and that MPPT generally outperforms PWM in cold to temperate climates such as Britain’s. For panels of 100 W or more, MPPT usually pays for itself.
• Battery. Lead-acid (AGM or gel) is cheap, heavy and best used to about half its capacity: Victron’s AGM data sheet gives 600 cycles at 50 percent discharge but 400 at 80 percent. LiFePO4 is lighter and longer-lived; Renogy rates its 12.8 V 100 Ah battery at 5,000 cycles to 80 percent depth of discharge, 9.9 kg, and charging only between 0 and 50 °C.
• Loads. 12 V devices directly (LED lights, pumps, cameras, USB chargers) or 230 V devices through a small inverter, which adds losses and its own standby draw.

A small grid-free system is different from a plug-in kit in one important respect. A plug-in kit feeds the house and uses its power at once; the battery is not part of it, and the rules forbid one. In an off-grid system the battery is the heart, and the panel exists to refill it after dull days.

Typical uses and the panel sizes they need

The loads below are typical figures to show the arithmetic; check the label or manual of your own device.

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Sheds and allotments. The most common use. Lights, a radio and charging take 100 to 200 Wh on an active day. Our guide to solar panel kits in the UK works through a heavier 400 Wh workshop example with tool charging; the smaller case appears below.

Garden lights. A single panel feeding a battery and several LED lights outperforms individual stake lights with their own tiny cells, because the panel can face south in full sun while the lights stand in shade.

CCTV and gates. Constant loads, every day of the year, which makes winter sizing decisive. A camera that records only on motion draws far less than one streaming continuously.

Electric fences. Common on farms and smallholdings. Energisers are rated in joules and current draw; the battery and panel are sized on the draw.

Caravans and boats. One to three panels of 100 to 200 W on the roof, through an MPPT controller to the leisure battery. In a marina or on a site with hook-up, the solar system normally charges the battery only and does not feed the hook-up supply.

Balconies. A small panel on a balcony charging a power station or 12 V battery is an appliance in use, not a generator connected to the house. If the aim is to lower the electricity bill, a compliant plug-in kit is the product to look at; see the plug-in section below.

Sizing a small off-grid system, step by step

Worked examples with real arithmetic

These examples combine hand calculation with PVGIS’s off-grid simulation, which models the battery day by day over many years and uses PVGIS’s default hourly consumption profile. The results are model outputs, not measurements, and the loads are assumptions.

Example 1: a 4G camera in Edinburgh, all year

Load. A camera averaging 5 W, 120 Wh a day.

Hand calculation. December yield at 35 degrees in Edinburgh is about 65 Wh per 100 W per day. 120 ÷ 65 × 100 ≈ 185 W of panel before any margin. For three days without sun on LiFePO4: 120 × 3 ÷ 0.8 = 450 Wh, or 35 Ah at 12.8 V.

Simulation. PVGIS tells a harsher story, because Scottish winters bring long runs of dull days, not single ones.

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Result. Quadrupling the battery behind a 100 W panel, even with the panel steepened to 70 degrees, still leaves the camera dark on almost half of January’s days. Doubling the panel to 200 W at a steep 70 degrees, with a 100 Ah battery, cuts empty days to about one in twenty-five in January. For winter reliability, panel area and tilt matter more than battery size. In London, the same simulation gave 2.5 percent empty days over the year with 100 W at 60 degrees and a 100 Ah battery, and 0.2 percent with 150 W.

Example 2: an electric fence near Manchester

Load. A 12 V energiser averaging about 100 mA, 29 Wh a day, run from a lead-acid leisure battery used to 50 percent.

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Result. A 20 W panel, often sold for fences, covers the summer but not the winter. A 40 W panel with an 80 Ah battery kept the fence live on every simulated day. A lead-acid battery that runs flat repeatedly loses capacity quickly, so the larger battery also protects itself.

Example 3: a weekend shed near Manchester

Load. Lights, a radio and charging, 150 Wh a day, with a LiFePO4 battery used to 20 percent.

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Result. For April to September, 100 W and a 50 Ah lithium battery are enough; the battery was full on more than four days in five in June, which means surplus energy went unused. For a shed used all year, 200 W at 60 degrees with 100 Ah is close to reliable. Since the shed is used at weekends rather than daily, the battery has five days to recover between visits, so these figures are conservative.

Example 4: garden lights in London

Load. Four 1 W LEDs for five hours, 20 Wh a day. With a 10 W panel at 60 degrees and a 6 Ah LiFePO4 battery (77 Wh), the battery ran empty on 77 percent of January days and 82 percent of December days. With 20 W and 12 Ah (154 Wh), that fell to 14 and 6 percent. Lights are wanted most in winter, when the sun is weakest, so a panel twice the size that the summer figures suggest is normal.

12 V wiring, cables and fuses

A 12 V system feels harmless because the voltage is low. The current is not. A battery can deliver hundreds of amps into a short circuit, enough to melt a cable and start a fire. Victron’s Wiring Unlimited sets out the rules most installers follow.

Fuse every circuit at the battery. Each consumer connected to a battery needs its own fuse in the positive cable, however small its power. A system usually has a main battery fuse and then individual fuses for each branch. Place them as close to the battery as practical, so that the cable between battery and fuse is short.

Fuse the panel side too. Victron says a fuse needs to be located between a PV array and the solar charger, and notes that regulations vary by application and country. Renogy lists a maximum series fuse rating of 15 A for its 100 W and 175 W panels, which sets the upper limit for any fuse protecting those panels.

Choose the fuse for the cable. With one consumer, the fuse matches the consumer’s current rating or the cable’s, whichever is lower; with several, it matches the cable. Use fuses rated for DC at the system voltage. Slow-blow fuses suit motors and inverters with high start-up currents.

Size cables for voltage drop. Victron advises aiming for a voltage drop of no more than 2.5 percent, 0.3 V on a 12 V system. The arithmetic uses copper’s resistivity, about 0.0175 ohm square millimetres per metre.

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At 4 mm², the usual solar cable size, the loss stays under 2 percent. The battery side carries more current at lower voltage: a 300 W inverter draws about 28 A from a 12 V battery at 90 percent efficiency, so keep that cable short and size it to the inverter’s manual.

Order of connection. Most controller manuals tell you to connect the battery to the controller first and the panel second, and to disconnect in reverse, so that the controller can detect the battery voltage. Follow your controller’s manual. Cover the panel or disconnect it before working on the wiring: a panel in daylight is always live.

When it becomes house wiring. A self-contained 12 V system in a shed, not connected to the house, is outside the plug-in solar rules and the network codes. Running a new 230 V circuit from the house to an outbuilding, by contrast, is notifiable electrical work in England under Part P of the Building Regulations and should be done by a registered electrician. Wiring an inverter to fixed 230 V sockets in a shed sits at the edge of these rules; follow BS 7671 and have an electrician check the earthing.

Mounting small panels

Small panels are light enough for DIY mounting, but wind is the main load. A 100 W panel presents about half a square metre to the wind; a 175 W panel almost 0.85 square metres. Renogy rates its 50 W panel for wind loads of 2,400 Pa and snow loads of 5,400 Pa, but that rating applies only if the mounting holds.

• Shed roofs. Z-brackets or tilt legs screwed into the roof structure, not just the felt or a thin sheet. On a felt roof, seal every fixing.
• Walls and fences. A vertical or steeply tilted panel on a south-facing wall is good for winter yield, as the table shows. Check the wall plugs and the fence posts; a panel on a weak fence panel can tear it off in a gale.
• Poles. Common for cameras and gates. A pole mount lets you set 60 to 70 degrees and keeps the panel out of reach.
• Vehicles and boats. Rigid panels on spoilers or brackets bonded or bolted to the roof; flexible panels bonded directly. Use fixings rated for the vehicle and marine-grade cable and connectors on boats.
• Ground stands. Weighted frames for allotments and gardens. Allow for shade from fences and hedges in winter, when shadows are long.

Avoid shade above all. Many small panels have only one or two bypass diodes, so shading one corner can cut output disproportionately.

Rules and permissions in the four nations

England

Planning: Class A of Part 14 of the permitted development order covers solar equipment on a house or block of flats and on a building within its curtilage, which includes a garden shed, subject to the same limits on projection and height and the exclusions for listed buildings and some conservation area sites. Free-standing panels fall under Class B, limited to 9 square metres of panel area, with height limits that tighten within 5 metres of the boundary. Amendments in force since 27 August 2026 (SI 2026/896) take plug-in solar on a wooden fence, gate, wall, balcony or other enclosure, or on a timber-clad part of a house, outside permitted development; those limitations are written for plug-in solar, not for off-grid panels, as our plug-in solar planning guide explains. Electrical work: see the Part P note above.

Scotland and Wales

Both nations have their own permitted development orders for domestic solar, with different projection limits from England; our guide to solar panel installation in the UK summarises them for houses. We did not find specific guidance on small panels on sheds or poles in either nation, so check with the council if a panel is large, prominent or near a listed building. Plug-in solar is legal in both since 27 August 2026 under the same UK rules as England.

Northern Ireland

Northern Ireland’s planning order allows roof-mounted solar on a dwelling or a building in its curtilage and a free-standing array of up to 14 square metres within limits, as summarised in our installation guide. Plug-in solar is not covered by SI 2026/848 in Northern Ireland, so a small panel there should stay off-grid.

Small panels and plug-in solar

Since 27 August 2026, plug-in solar has been legal in England, Scotland and Wales under SI 2026/848, which makes the government’s Interim Product Specification v2.0 binding. A plug-in device may have up to 800 W of output and up to 2,000 W of panels in at most four modules, no more than two in series and no more than 120 V DC. It must have a moulded 13 A plug, no battery, a listing on the ENA Type Test Register, and be the only such device in the household, and it must be notified to the network operator. Above 960 W of panels, manufacturers must advise you to consider a professional assessment of your wiring.

Two consequences follow for small panels.

A plug-in kit is a complete registered product. The specification defines the device as the set of panels, inverter, plug lead, cables and mounting, confirmed as compliant by the manufacturer. A kit can use smaller modules if its manufacturer designed and registered it that way. Adding your own small panels to a microinverter does not create a compliant device, as we read the rules. Our guide to whether plug-in solar is legal in the UK sets out every condition, and our guide to choosing a plug-in solar kit covers what to look for.

12 V panels and microinverters rarely match. Plug-in microinverters are designed for panels of 30 to 45 V. APsystems’ EZ1-M data sheet, for example, gives an MPPT voltage range of 28 to 45 V. A single 12 V class panel at around 20 V sits below that window and would not run the inverter properly; two in series reach about 40 V but deliver far less current than the inverter is built for. This is one reason plug-in kits use roof-size modules.

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What small panels cost

Small panels are cheap to buy and expensive per watt. A frame, glass sheet, junction box, cables and packaging cost almost as much for a 50 W panel as for a 200 W one. The prices below are market observations from retailer and manufacturer pages on 4 November 2026, not recommendations.

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For a 100 W shed system, the panel is rarely the largest cost: panel, MPPT controller and a 100 Ah lithium battery come to about £330 before cable, fuses and brackets at these prices. Retail panels carry the standard 20 % VAT; HMRC’s zero rate applies only to the installation of solar panels in residential accommodation by an installer, not to panels bought on their own.

Buying checklist: what the data sheet must show

• Pmax, Vmp, Imp, Voc and Isc. Without these five values you cannot match a controller or power station. A listing without a data sheet is a warning sign.
• Voltage class. 36 cells for a 12 V battery, 60 to 72 cells for 24 V systems and inverters. Check that the open-circuit voltage on a frosty morning, about 10 percent above the data-sheet value, stays below the controller’s input limit.
• Short-circuit current against the controller. The controller’s maximum PV short-circuit current must exceed the panel’s Isc, or it may be damaged.
• Dimensions and weight. They decide the bracket, the fixings and the wind load.
• Maximum series fuse rating. It sets the fuse on the panel side.
• Connectors and cable. MC4-type connectors are common; some small panels come with bare leads or none. Mating connectors should come from the same manufacturer.
• Warranty. Product warranty in years and the output guarantee. Five to ten years on the product is usual for small panels.
• Bypass diodes. They limit losses from partial shade; very small panels sometimes have none.

Common mistakes and edge cases

• Sizing on annual yield. Consequence: a battery that is flat from November to February. Fix: size on the weakest month you need, using the table or a PVGIS simulation.
• A shallow tilt for a winter load. Consequence: half the December yield of a steep panel. Fix: 60 to 70 degrees for year-round use.
• Bigger battery instead of bigger panel. Consequence: in a long dull spell the larger battery simply takes longer to empty and never refills. Fix: add panel first, as the camera example shows.
• No fuse at the battery. Consequence: a cable fire if the wiring shorts. Fix: a DC fuse in each positive cable, close to the battery.
• Thin cable over a long run. Consequence: several percent of the energy lost as heat. Fix: 4 mm² or more for runs of several metres.
• PWM controller on a larger panel. Consequence: about a fifth of the panel’s power wasted in cool weather. Fix: MPPT from about 100 W.
• Charging lithium below freezing. Consequence: permanent cell damage. Fix: a battery with low-temperature protection or self-heating, or a controller with a temperature sensor.
• Wiring a small panel into a socket. Consequence: an unlawful and dangerous connection. Fix: keep the system off-grid, or buy a registered plug-in kit.

Durability, maintenance and recycling

Rigid glass panels are the most durable choice; Victron’s output guarantee of 80 percent after 25 years shows the expected life. Clean them when bird droppings or moss shade part of the surface, because a small panel with few bypass diodes loses more than its shaded share. Check fixings after storms and connectors once a year for corrosion, particularly on boats.

Batteries wear faster than panels. Lead-acid batteries age quickly in heat and when run flat, and lithium batteries when charged in the cold. Controllers and inverters, like any electronics, have shorter warranties than panels.

At the end of their life, panels, controllers and batteries are electrical waste. Take them to a household waste recycling centre or a retailer take-back scheme, never the household bin.

Next steps

• Solar panel kits in the UK compared: plug-in, off-grid and battery
• Off-grid solar systems in the UK
• Solar panel sizes in the UK: dimensions and roof fit