Usually yes, if you can charge the battery in the cheap window — but the tariff landscape has more options than it used to, so it's worth understanding the full menu. The classic play is a day/night or dedicated EV tariff: you charge the battery overnight at a low rate (often somewhere around 8–14c on an EV plan) and run the house off it through the expensive daytime and evening hours, on top of whatever your panels generate. For a home that can shift a decent chunk of load that way, it stacks well with solar.
The newer option, live since 1 June 2026, is dynamic (half-hourly wholesale) pricing, where the rate updates every 30 minutes and the day-ahead prices are published in advance. With a battery and a bit of automation you can chase the genuinely cheapest half-hours rather than a single fixed 2–5am window — potentially squeezing more out of windy, low-price overnight periods. The trade-off is that it rewards automation and discipline; a simple fixed night/EV window is more predictable and may still win if you can't reliably move load.
So the choice is now flat-rate vs day/night vs a dedicated EV window vs dynamic — and the right answer depends on your own usage shape. The single most useful thing you can do is download your half-hourly (HDF) data from ESB Networks and model each option against how much load you can actually shift. Watch the standing charge too: smart/EV tariffs often carry a higher daily charge that only pays off if you genuinely use the cheap window.