JournalArticleSolar2 min read
Batteries and the hours after sunset
Solar panels produce most of their energy around midday, while many homes use most of theirs in the evening. Batteries bridge that gap, at a cost worth understanding.
A rooftop solar system follows the sun. Its output rises through the morning, peaks around noon and fades in the late afternoon. Most households follow a different rhythm, with demand climbing in the evening when people come home and the bedrooms are cooled for the night.
Without storage, energy produced at midday has to be used at midday. Since the 2024 changes to Indonesia's rooftop solar rules, surplus power sent to the PLN grid no longer reduces your bill, which makes that question of timing more important than it used to be.
What a battery does
A home battery stores part of the midday surplus and releases it after sunset. Paired with a hybrid inverter, it can also keep essential circuits running during a power cut, which many people in Bali value as much as the savings.
Most current home systems use lithium iron phosphate cells, usually shortened to LFP. They are more stable than older lithium chemistries and can be cycled thousands of times over their working life.
Sizing it sensibly
The right battery size follows from your evening consumption. The size of your roof matters much less. If your home uses eight kilowatt hours between sunset and midnight, a battery far larger than that will rarely be filled or emptied completely, and the extra capacity is money spent without return. A useful first step is to look at a few months of electricity use and estimate how much of it falls after dark.
Batteries prefer shade and moving air, which is a design decision long before it is an installation one.
Where it lives
Heat shortens battery life. A ventilated plant room or a shaded wall on the cool side of the house will serve a battery far better than a hot cupboard or a wall in afternoon sun. This is one more reason to plan for storage while the building is being designed, even if the battery itself arrives years later.
When it pays
Batteries are still a significant investment. Whether they pay back depends on the gap between your daytime production and your evening use, and on how much you value having power during an outage. For some homes the case is clear. For others, a well sized system without storage is the better first step.
BODE Solar is in its first season and is focused on explaining these choices clearly before recommending any equipment. You can follow that work on the BODE Solar site.
