"Keep for peak" usually costs you money | PredBat

"Keep for peak" sounds prudent, and that is the problem with it. It asks PredBat to still be holding charge when the expensive evening period arrives, but charge held back is charge that was not exported into the peak and not used in place of importing at peak prices. On an export-led tariff the right value is normally zero. From 5 September the dashboard says so while you move the control: an advisory above 10 percent, and a stronger warning above 90 percent. It is not the same as the minimum next to it The two controls sit together and both hold charge back, which is why they get confused. The minimum is a hard floor: a level the battery is never discharged below, so that there is something left if the power goes out. It is a deliberate trade of savings for backup, and if that is what you want, it is doing its job. Keep for peak is a preference rather than a floor, and it is not a reserve. Nothing is locked away: PredBat treats dropping below the level as though it costs money, and will still do it when the saving is worth more. It also never imports from the grid to top back up to the level. What it does is bias the whole plan, ramping in over about four hours rather than acting only at the peak. Why a very high value makes every slot say Hold Charge Because it is a preference rather than a hard limit, a high value does not forbid the plan from spending charge. It makes spending look expensive. Set at or near the battery's usable capacity, that penalty outweighs almost every alternative the optimiser can find, and the practical result is a plan in which every slot reads "Hold Charge": the battery sits full and the house runs on grid import, including through the peak. That state is legible once you know to look for it, and invisible otherwise, which is why it now carries a warning rather than waiting for someone to work it out from their bill. The warnings read the value, not the gesture The warnings are worked out from what keep would be worth if it were committed at that instant, and they update as you move the control rather than after a change is saved. That distinction matters in two directions. A keep sitting at or below your minimum is dormant, because the hard floor already holds that charge, so it no longer produces a warning about a setting that is changing nothing. In the other direction, moving the minimum can no longer save the keep handle's parked position as a real setting. That was a way the costly value could be created by a gesture aimed entirely at the other control, without the person making it ever choosing a keep level at all.