Set the panel to 40° and you are within a degree of right for four in five places in the UK. PVGIS measured the best angle for 2,929 of the UK's postcode districts, and it barely moves from one end of the country to the other: 38° at Truro, 40° across London and in Edinburgh, 43° at Wick. Unlike a touring van, a caravan sits on its pitch for days, and that is what makes tilting worth the effort: at British latitudes it gains 12% to 21% of midday direct sun in summer and 250% to 569% in midwinter.
Do not use the old rule of tilting to your latitude. It is close enough in the south of Europe and it runs steadily too steep as you go north: at 52° it would put you at 52° when the measured optimum there is 40°, twelve degrees out. Even a curve fitted to PVGIS's data for the whole world runs about two degrees too steep over Britain, which is why the figures here are the measured ones. Look up your postcode district for its own figure: a valley pitch can want much less, and Glencoe measures 25°.
For a pitch you use through the winter, go much steeper than the annual figure: 63.0° at 50° north rising to 70.0° at 58°. That is about 23° to 28° above the year-round angle, not the 15° the rule of thumb suggests, because a British midwinter sun is very low. In high summer drop to between 25.5° and 32.9°.
| Latitude | Midsummer | Spring and autumn | Midwinter |
|---|---|---|---|
| 50° (Cornwall, Brighton) | +12% | +56% | +250% |
| 52° (mid Wales, Norfolk) | +14% | +62% | +297% |
| 54° (Lake District, York) | +16% | +70% | +358% |
| 56° (Stirling, Perth) | +19% | +79% | +444% |
| 58° (Ullapool, Wick) | +21% | +89% | +569% |
These are midday, clear-sky ceilings for direct sun, computed from the sun's noon elevation. British cloud pulls the real daily figure well below them, which is exactly why the winter numbers matter: when there is little direct sun to collect, giving up two thirds of what does arrive is expensive. For the exact monthly angle at a site, look it up by postcode or town name.
More often than on a campervan, and for one reason: the van moves, the caravan does not. A tourer that parks somewhere new each night rarely justifies getting the legs out. A caravan on a weekly or seasonal pitch is set up once and left, so the gain runs for days instead of hours.
The season decides the rest. In June a tilt buys you 12% to 21% at midday, which is real but not worth climbing up for on a two-night stop. From October to February it multiplies what a flat panel collects, and that is when a leisure battery is under the most strain and the site hookup is most likely to be off.
True south, which sits a couple of degrees off compass south in Britain. If the pitch will not allow it, do not give up and lie the panel flat: facing somewhat east or west costs far less in winter than being flat does. Point the awning side away from south if you can, so the panel is not shaded by your own outfit through the middle of the day.
A bonded roof panel cannot tilt, so it takes the flat figures in reverse: in December it collects what the midwinter column says it gives up. That is not an argument against fixed panels, which need no setup and cannot blow away. It is an argument for sizing a fixed installation by the winter number rather than the summer one, the same way an off-grid cabin is sized.