How to Read the VoltSun Charge Planner: A Card-by-Card Guide
Five data panels, one decision: when to plug in. This guide explains what each number, chart, and score in the Charge Planner actually means — and how to act on it.
What the Charge Planner Does
The VoltSun Charge Planner combines two live data streams — solar radiation forecasts and electricity price patterns — and surfaces one actionable output: the best time window to charge your EV today and over the next seven days.
You don't need to understand the underlying data to use it. But knowing what each card is measuring helps you make better decisions, especially on marginal days when the numbers are close.
Optimal Charging Window
This is the card you open the planner to see. It shows a specific time window — typically two to four hours — when the combination of high solar production and low electricity price makes charging most efficient.
The score (0–100) is the key number. It's a composite rating: higher solar radiation and lower electricity price both push the score up. A score above 70 is a genuinely good window; below 40, conditions are marginal.
The arc gauge visualizes the score on a 270° dial. A nearly full arc means excellent conditions; a thin sliver means the best window available today isn't particularly strong.
Hour pills show each individual hour inside the window. If the window runs 11:00–14:00, you'll see three pills. The pill highlighted in green is the current hour — useful for knowing whether you're already inside the window or approaching it.
ACTIVE NOW / TODAY badges tell you the window's status at a glance. "Active Now" means plug in immediately. "Today" means the window has passed for today — plan for tomorrow instead.
The reason text below the time display gives a plain-language explanation of why the algorithm chose this window: "High solar output with low grid price," "Peak solar — moderate price," and similar.
Solar Forecast
This card tells you how much solar energy is available at your location today, expressed in kWh per m².
The level label (Excellent / Good / Fair / Poor) maps to four ranges:
- Excellent: above 8 kWh — clear or mostly clear sky, full summer output
- Good: 5–8 kWh — partly cloudy, solid output
- Fair: 2–5 kWh — significant cloud cover, reduced but usable output
- Poor: below 2 kWh — heavy overcast, minimal solar contribution
Sun hours shows how many hours of meaningful daylight your location has today (from sunrise to sunset). This is different from peak sun hours — it's the window during which any solar production occurs at all.
Cloud cover % is the average cloud fraction across the day. 30% cloud cover and 70% cloud cover produce very different output curves even when total kWh looks similar, because cloud density matters as much as cloud fraction.
Clarity % is the inverse of cloud cover — it's the percentage of the day that's clear. A high clarity reading with a long sun hours window means your optimal charging window should align closely with peak solar.
The progress bar shows today's forecast against a ceiling of 12 kWh — a strong midsummer day in central or southern Europe. In winter, expect bars at 15–25% of that maximum.
Electricity Price
This card shows the current electricity price for your country and where it sits relative to the daily range.
The price meter has three segments: Low (green), Medium (amber), High (orange). The active segment is the one that matches current conditions. This is intentionally simplified — for EV charging decisions, you need to know whether now is cheap or expensive, not the exact per-kWh figure down to four decimal places.
Current hour price is the rate your grid charges right now, estimated from typical time-of-use (TOU) patterns for your country. Grid prices follow predictable shapes: low overnight and early morning, rising through the morning peak, dipping midday, spiking in the evening. The Charge Planner models this curve rather than pulling live spot prices, which means the pattern is reliable even if the exact figure differs slightly from your specific tariff.
Average price is shown below the meter as a reference point. If the current price is below the average, you're in a favorable charging window from a cost perspective regardless of solar.
Today — Hour by Hour
The most information-dense panel in the planner. It overlays two data series across 24 hours on the same chart.
The yellow area is solar radiation — the amount of sunlight energy reaching the ground at your location, hour by hour. It rises after sunrise, peaks around solar noon (typically 12:00–13:00 in most of Europe), and falls to zero at sunset. The shape of this curve is what the planner uses to identify when solar panels would be producing at peak output.
The blue dashed line is the electricity price curve across the day. It moves somewhat independently from the solar curve. The best charging windows occur where the yellow area is high and the blue line is low — visually, where the two curves diverge most in your favor.
The green shaded region marks the optimal window. This is the same window shown on the first card, visualized in context. You can see exactly where it sits relative to both the solar peak and the price curve.
The white dashed vertical line is the current time. Everything to its left has already happened today; everything to its right is the forecast.
Hovering over any hour shows a tooltip with exact solar radiation (W/m²), electricity price, and a per-hour score — useful if you want to find a slightly different window that fits your schedule better than the recommended one.
7-Day Solar Forecast
This chart answers a different question: not when to charge today, but which days this week are worth prioritizing for solar charging.
Each bar represents one day. Bar height corresponds to total solar energy (MJ/m²) for that day. The color follows the same level system as the Solar Forecast card — lime yellow for Excellent, amber for Good, orange for Fair, grey for Poor.
Today's bar is underlined to orient you in the week. Days with Poor or Fair forecasts are worth flagging in advance: if you have flexibility in when you charge, plan heavier charging sessions on Excellent or Good days and minimize grid use on Poor days.
This is especially useful for households with home batteries. A week with three Excellent days followed by two Poor days tells you to charge the battery fully on the good days and draw from storage on the bad ones.
Reading the Dashboard as a Whole
The five panels work together:
- High score + Excellent solar + Low price → ideal day, plug in during the recommended window
- Moderate score + Fair solar + Medium price → fine to charge, but less critical to time it precisely
- Low score + Poor solar + High price → consider delaying if possible; use overnight off-peak instead
- 7-day shows a better day ahead → if you have enough range, wait for a higher-score day
The Charge Planner updates every morning with new solar forecast data. Check it at the start of the day and set a reminder for the start of the optimal window — that's the full workflow.