Features → Why it waits

Why it waits

The most common first-day reaction to Sunplug is that it seems slow. It is slow on purpose, the delays are measured rather than guessed, and shorter ones would put less energy in your car.

A cloud is not a sunset

On a partly cloudy afternoon your production graph is a saw. A cloud takes four kilowatts off the roof for ninety seconds and then gives them back. If Sunplug reacted to that, it would stop your car, wait, restart it, and repeat — perhaps thirty times before dinner.

Each of those cycles costs more than it sounds. A charge does not resume instantly: the car and the wallbox negotiate, and a Tesla Wall Connector takes about five minutes to ramp back to full current. So a stop-start that saved you ninety seconds of grid import costs you five minutes of charging — and does it thirty times.

That is the whole argument. The delays are not caution about getting it wrong; they are what makes the total energy delivered larger.

The four numbers

Six minutes before stopping

Surplus has to be genuinely insufficient for six continuous minutes before a running charge is stopped. Long enough to sit out any normal cloud, short enough that a real sunset is not spent importing.

Fifteen minutes before restarting

Longer than the stop delay, deliberately and asymmetrically. Stopping is cheap and reversible; starting costs a wake, a negotiation and a ramp. When the two delays were equal, a marginal afternoon produced a car that spent more time ramping than charging.

Three minutes between current changes

While a car is charging, Sunplug adjusts its current rather than stopping it — but not continuously. Each change is a command over the network to a car or a wallbox, and on some cars it is a command you are billed for. Three minutes tracks the sun closely enough that the error is small, without spending a request every thirty seconds on a change of one amp.

Three readings before believing a change

A single reading can be wrong — a meter glitch, a truncated response, an inverter restarting. A change has to persist across three consecutive readings before Sunplug acts on it. One bad number changes nothing at all.

What it does not wait for

Two things happen immediately, because in both cases waiting is the dangerous choice.

Exceeding an electrical limit. If the combined draw would go over what your supply allows, current comes down that tick. No delay, no confirmation — the delays exist to avoid wasted effort, and a tripped breaker is not wasted effort, it is your lights going out.

A reading going stale. If the solar data is more than five minutes old, Sunplug stops treating it as true. It does not keep charging on the last number it saw; it fails the cars safe to zero and says so in the reason. An old reading is not a small error — a house that was exporting four kilowatts when the agent went quiet may have put the oven on since. What happens when it goes blind →

Should you change them?

They are adjustable, and mostly you should not. The two worth understanding before touching:

• Shortening the stop delay makes Sunplug more responsive to cloud and delivers less energy. This is the one people reach for first and regret.
• Lengthening the restart delay is occasionally right if your wallbox is unusually slow to ramp — you would know, because you would have watched it.

If a delay feels wrong, the decisions view is the thing to look at first. It records what the surplus actually was at each tick, so "it should have started at two o'clock" becomes a question with an answer.

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