A time-of-use rate charges a different price for electricity at different hours. Solar that lands at noon and a household that needs power in the evening are then on different rows of the tariff. A battery can move midday energy into the evening. It can also do nothing useful if the evening price and the midday export price are close, or if the battery is reserved for outages and is not allowed to cycle daily.
The tariff has to be in front of you
Net metering that banks exported kilowatt-hours against later purchases already moves the energy, on paper, without a battery. Net billing that pays exports at a low sell rate and charges purchases at a high evening rate is the case where a battery has something to arbitrage. The distinction, with a labeled numerical example, is in what net metering means. Do not paste that example’s cents onto your utility. Read the schedule.
Demand charges, which bill the highest short burst of power rather than the hour, are a different line and matter more on many commercial meters. They are in what a demand charge does. A residential time-of-use energy rate and a commercial demand charge can both appear on a bill. They are not two names for one fee.
What the battery has to survive
Daily shifting is a cycle, most days, for years. The sheet has to allow that depth and that throughput. A warranty written for backup use is not automatically a warranty for a full cycle every afternoon. Cycle life and the calendar clock are in cycle life and calendar life. Round-trip loss means you put in more kilowatt-hours than you get back. If the price gap is smaller than that loss, the cycle costs money even before the battery’s price.
The payback arithmetic that can hold an operating cost and a split between self-use and export is in how a solar payback period is calculated. This page will not run a second national example. Bring your peak price, your off-peak price, and the usable kilowatt-hours. If you do not have the prices, you do not yet know whether the battery is a bill tool or only an outage tool.
Reserve and shift are two settings
A battery held at a high state of charge for outages does little time-of-use work. A battery emptied every evening has less left if the outage arrives at 6 p.m. The inverter setting that chooses between those two jobs is part of the purchase, and it has to be one the battery communication actually allows. Voltage-only control that ignores the pack’s own limits is how a “smart” schedule over-discharges a battery the sheet did not permit. Communication between the two is in battery and inverter communication.
Seasons move the gap. A summer evening peak and a winter evening peak are not the same length, and solar production is not the same either. A schedule copied from a forum in another climate can charge the battery from the grid at the expensive hour, which is the opposite of the plan. Read the months on your own tariff. If the utility changes the windows, the old schedule is no longer the one you modeled.
