Planning Around the Sun You're Going to Get

Each of the next three days arrives with a charging verdict, the power to expect, and the hours actually worth being set up for. That is enough to plan against — whether to stay or move on, whether to spend tonight's battery or bank it, and which day to be at camp with the panel out.

The decisions it changes

A strong day tomorrow means tonight's shortfall is temporary, so you can run the fridge hard and stop rationing. Two poor days behind a good one is the signal to fill the bank now — charge on the next drive, and set the panel properly for the good hours instead of leaving it flat beside the awning. Three ordinary days in a row and it stops being a solar question: you ease off, move somewhere more open, or leave a day earlier than planned.

None of those can be decided on the morning they matter. They all need a day or two of notice, which is the whole reason the card is there. Getting the most out of your solar is only the means — staying out longer, with the comforts you rely on, is the reason.

Each day gives you its hours, not just its mood

This is the part that turns a forecast into a plan. Every day carries its own best charging window, as a plain time range — 9am – 2pm. The same idea as the Best Charging Window you use for today, worked out for a day that has not arrived.

Knowing Thursday is Good is nearly useless on its own. Knowing Thursday's good window is done by two in the afternoon is a plan: you take the walk in the morning or you take it after, and the panel gets the hours either way. Both that window and the W/m² figure beside it are Pro.

Each of the three columns carries the same things: the day, a sky icon, the verdict word, that day's W/m², its best window, and its own sunrise and sunset. Under the three, one line gives the average daylight across them — a quick read on whether the light itself is growing or shrinking on you, which is worth a glance in the weeks either side of a solstice.

Open a day when the plan hinges on it

Tapping a day — a Pro move — breaks it into hours, which matters when an average hides the shape.

A day that grades out as Fair is often a clear morning and a clouded-over afternoon. As one word that reads as mediocre and you would write the day off. Opened up, it is a genuinely good four hours to build a setup around and a rest of the day to ignore. The hour-by-hour strip along the bottom is where that shows — an icon, a temperature and a cloud reading for every step of daylight, so you can see exactly when the day turns.

The opened day also carries rise, noon and set; the daylight hours; the day's cloud; Peak Alt — how high the sun climbs, which decides whether the day wants a steep panel angle or a shallow one; and Good Sun.

What Good Sun counts

Good Sun is how much of the day's daylight is bright enough to grade Good or better — above 300 W/m² — expressed in hours. It carries a tilde on purpose: it is worked out from the forecast's own steps and scaled across the daylight, so it is a close estimate rather than a count off a clock. It is not the length of the best window, and the two are worked out separately, so they will not always agree.

A day with a bright morning, a dull middle and a bright late afternoon has more good hours than its window is wide: the window is one unbroken run, while Good Sun counts the good hours wherever they fall. It can go the other way too — a window rides through a short dip rather than breaking in two, so it can be wider than the hours it contains.

The numbers, so you can trust the plan

The verdict is not a mood. It is a W/m² band — the sunlight landing on each square metre of ground where you are: Excellent is 500 and up, Good from 300, Fair from 150, and Poor below. The day's figure is an average across its daylight, weighted toward the hours the sun sits highest, so a dim half-hour at dawn cannot drag a strong day down.

That W/m² is not something a weather station sends you. Your phone works it out for each hour, from the forecast's cloud and rain and how high the sun will be at your own spot on that date. It is why the same cloud figure grades differently in midwinter than in midsummer, and differently again at a latitude far from your own.

One thing worth knowing before it confuses you: the figure on the three-day strip is each day's peak, not that average. Open the day and you get both, labelled avg W/m² and peak W/m². A strong peak under a middling word is not a glitch — it is a good hour or two inside an ordinary day, and it is your cue to open that day up.

One wording note, so the app never looks like it is contradicting itself: the 150–300 band reads Fair on the outlook and Moderate in the W/m² explainer on your main screen. Same band, same numbers, two words.

It is a different question again from the sky rating on your main screen. That one measures how much of the available light the sky is letting through, so a cloudless midwinter noon scores full marks on a third of the energy a midsummer one brings. The sky rating grades the sky; these bands grade the watts.

It won't tell you it's cloudy when it isn't

Wherever the app writes a sentence about a day — at the foot of an opened day, and under tomorrow's card on the free tier — that sentence is built from two separate truths: the sky from the forecast's cloud, the charging outlook from the W/m². Neither is allowed to speak for the other. The three-day strip itself carries no sentence; there it is the verdict word and the numbers.

The case it exists for is the one that would cost you trust. A crisp 10%-cloud winter morning can still be a poor charging day, because the sun is low and the day is short. Stated as one canned phrase you get "Heavy cloud — limited charging expected" on a day the reader can see is blue — and every other number on the screen goes down with it. Instead you get Clear but low sun. Plans are only as good as the numbers under them.

Out of range, it still has three days for you

Half of this card never needs a signal at all. Sunrise, solar noon, sunset, the daylight hours and Peak Alt are worked out on the phone from where you are and the date — no forecast involved, and exactly as right on day three as on day one. Cloud and W/m² are the half that comes from a weather forecast, and that needs a connection to refresh.

Lose the connection — or switch Bush Bash Mode on deliberately — and the app does not blank the card. It serves the last forecast that landed, so the three days keep their verdicts, their windows and their W/m², and you can still plan against them.

The banner at the top of the main screen carries that reading's age as Last sync, and it is the line to look at before you trust the days under it. A forecast that landed this morning is still a good plan for the next three days. One from four days back is labelled with days that have already been and gone, and it cannot know it.

If nothing has ever been stored — a first run with no signal — the app says so rather than inventing a day: Forecast not yet available — sun times above are calculated and accurate. The sun times stay, because they were never the part that needed a signal.

What free gets, what Pro adds

• Free Tomorrow, on the main screen under the sun diagram. The verdict and its caption, Good Sun hours, cloud, average temperature and the sun times. A real forecast, graded on the same W/m² bands Pro uses — not a locked preview of one.
• Pro Three days instead of one, each opening to its hour-by-hour detail.
• Pro A best charging window worked out for every one of those days, and the W/m² figures behind each verdict.
• Pro A finer forecast underneath. Pro reads the sky hour by hour; free gets it in three-hour steps. Both are graded the same way, but a day judged on a handful of three-hour steps can miss a mid-morning clearance that hourly data shows plainly.

One thing not to read too much into on the free card: the range printed under its Peak Window heading is a fixed middle-of-the-day rule of thumb, not a window worked out for your day. The window that moves with the weather is the Pro one, and there is one for each of the three days.

Why it stops at three days

Because that is about as far as a solar forecast stays worth acting on. Past it you are planning against a guess in a forecast's clothing, and a guess you commit to costs more than no number at all. Seven-day icons are everywhere; what is harder to find is anyone willing to say how much of day six they would stake a night's power on.

Three is the ceiling rather than a promise. If the forecast in hand does not reach that far, the day is left out of the strip rather than filled in with a guess, so now and again you will find two columns instead of three — most likely just after a cold start, or offline on an older reading. The days that are there are real; the missing one is missing on purpose.

Two limits worth having straight. The verdict grades what is available, not what you will capture. An Excellent day with the panel flat in the shade of the awning is still a poor day for your battery, and the outlook cannot know you have done that. And it does not know your site — the trees, the valley wall, the ridge to your east. It gives you the sun; you supply the ground.

Plan the days, not just the morning

Tomorrow's outlook is on your main screen right now, free. Three days, each with its own best window and each opening to the hour, is part of Solar Spotter Pro — a one-off purchase, no subscription, and your data stays on your phone.