SOLAR YIELD MODEL
Solar Yield Calculator
Set your panel size, pick the time of year and the weather, then drag the sun across the sky to see what your panels actually put out. Built on the same solar model we run inside the TITAN app.
Average day for each month at your latitude, panel size and weather. Drag the month slider to scrub through it.
How much solar do you actually need?
There is no single answer. It comes down to what you run and where you park. As a rough guide, a fridge, a few lights and charging your phones is around 600Wh a day. Add a diesel heater on its fan, a sizeable inverter or Starlink and you are nearer 1,000 to 1,500Wh. Put your own figure into the daily-use box above and the tool tells you whether the panels keep up or whether you will be drawing the battery down.
Brochure watts are not road watts
A 200W panel is rated at 200W in a lab, at 25°C, under bright midday sun pointed straight at it. On a van roof in the UK you rarely see all of that at once. The sun sits lower, the panel runs hot, and cloud takes its cut. That is why a flat 200W panel on a clear June day averages around 1kWh, not the 2kWh the daylight hours might suggest. This calculator works in real angles and real weather so the number you get is one you can plan around.
What the seasons do to it
The sun's height is everything. In a UK summer it climbs to about 60 degrees at noon and you get long, productive days. By December it barely reaches 13 degrees, the light has far more atmosphere to push through, and a flat panel might only return a fifth of its summer figure. The year chart above shows that swing month by month. Tilting a panel towards a low winter sun claws a lot of that back, which is why a portable or adjustable panel earns its keep off-season.
Pairing solar with a TITAN battery
Solar tops the battery up through the day so you can run the evening off it. The bigger the battery, the more of a sunny day you can bank for later, and lithium will happily sit part-charged for weeks without harm. Pick a battery above and the readout shows how much of it a day's sun refills and how long it takes from empty. To go the other way and size the battery to your kit, use the battery size calculator. If you are charging from the alternator as well, our range of compatible chargers covers the lot.
Common questions
How much power will I get from a 200W panel on a campervan?
On a clear UK summer day a flat 200W roof panel averages roughly 1.0 to 1.1kWh, peaking near 120 to 140W around midday. In winter, or under heavy cloud, that can drop below 200Wh. Tilting the panel towards the sun makes a real difference at low sun angles.
Why does cloud cut solar yield so hard?
Cloud blocks the direct beam, and the direct beam carries most of the energy. A clear sky at UK summer noon gives around 600 to 800 W/m2; overcast usually falls to 50 to 150, roughly a fifth of that. Low, thick cloud hurts far more than high, thin cirrus.
How long will solar take to recharge my leisure battery?
Divide the battery's energy in watt-hours by the panel's daily yield. A TITAN 105Ah holds about 1.34kWh, so a 200W panel making 1kWh on a clear summer day refills it from empty in a little over a day, assuming you are not drawing from it at the same time. Pick your battery above for the figure that fits your setup.
Does it work with a Victron MPPT and Truma panels?
Yes, and that is exactly what the figures are based on. A monocrystalline Truma panel on a Victron SmartSolar MPPT is a common, sensible setup. The Victron tracks at about 98% efficiency, so most of the loss between the panel rating and the battery is down to panel temperature and cabling, which the calculator accounts for.
Will solar keep my battery topped up over winter?
On its own, rarely, at UK latitudes. A short, low-sun December day gives very little from a flat panel. Most owners lean on the alternator or a mains charger over winter and treat solar as a strong contributor from spring to autumn. A tilted panel and a healthy lithium battery narrow the gap.
