Controls decide whether a heat battery uses cheap energy at the right time or quietly tops up at an expensive rate. They deserve the same attention as capacity and insulation.
The short answer
A useful control system shows when the store will charge, how much energy remains, why a boost started and what happens when connectivity fails. The household should be able to make a safe temporary override without losing the basic schedule.
Fixed schedules
Economy 7 and fixed time-of-use tariffs can often use a repeating schedule. Confirm the meter's actual off-peak times, clock changes and whether the circuit is meter-switched or permanently live.
Dynamic prices
Variable tariffs need price data and a rule for choosing charge periods. Ask whether the optimiser considers the next heat demand, maximum charging power and a minimum reserve.
Design the failure mode
If Wi-Fi, a cloud service or price feed disappears, the unit should fall back to a known behaviour. “No charge” and “charge immediately” create very different comfort and cost risks.
Avoid invisible boosts
Automatic top-up can protect hot-water availability but undermine savings. The app or display should record when boosts occur and the tariff period used.
Household access
Check whether controls require a smartphone, whether more than one person can use them and what happens when the phone or property changes owner.
Your next step
Ask the installer to write the default schedule, boost rule and offline behaviour on the commissioning sheet. Review actual charging after the first busy week.
Sources
Primary and independent references checked by our editorial team.
- Economy 7 tariff guidance — Ofgem Checked 10 Nov 2026
- Get help with your smart meter — Ofgem Checked 10 Nov 2026