Two-rate electricity tariffs can be brilliant when your usage happens overnight and expensive when it does not. The question is not whether the cheap rate is cheap. It is whether enough of your kWh moves into it.
Night useThe key input
EV awareCharging load included
Single vs two-rateAnnual cost compared
RTS warningMeter compatibility matters
Rules of thumb
When Economy 7 or EV tariffs help
Likely good fit
Storage heaters, immersion heating, EV charging, battery charging or appliance timers shift a large share of use into off-peak hours.
Likely poor fit
Most usage happens in the evening peak, and the day rate is much higher than a single-rate tariff.
Meter compatibility
Ofgem says Economy 7 requires a meter that records peak and off-peak usage separately.