Do I need a battery or are panels enough?

Panels alone are genuinely enough for many homes: if someone is in during the day, big loads can run at noon, and your export rate is decent, self-consumption plus a fair export deal captures most of the value. A battery earns its keep when the opposite holds — evening-heavy consumption, a wide gap between import and export prices, or a time-of-use tariff it can arbitrage.

Why “it depends” has a precise shape

The battery’s income is arithmetic, not magic: (import price − export price) × the kWh it realistically shifts per day. A daytime-active household with an EV charging at noon and hot water on a diverter may already self-consume half its production — leaving the battery only scraps to shift, and a long payback. An out-at-work household exporting 70% cheap and importing evenings dear hands the battery a fat daily spread.

Two regional notes sharpen it. Where export rates are relatively strong (some UK fixed SEG offers, Ireland’s CEG at its better rates), panels-only economics improve — exporting is not the disaster it is under token feed-in rates. Where TOU/dynamic tariffs are mature (UK, Australia), the battery earns twice: solar shifting by day, cheap-window arbitrage by night — see the overnight-charging answer.

What to do

1. Get your three numbers: evening-and-night import (kWh/day), export share of production (%), and your import-export price gap. High-high-wide = battery. Low-low-narrow = panels are enough.
2. Exhaust the free shifts first — timers and automations for water, laundry and EV cost little and shrink exactly the problem a battery would be bought for (see the self-consumption guide).
3. Re-run the numbers after a tariff switch — a move to TOU can flip the battery verdict on its own.
4. If it is close, wait deliberately — battery prices keep drifting down; a borderline case this year is often a clear case next. Meanwhile a production forecast shows how much surplus you actually strand each week — the most honest input to the decision.