Off-Peak Hot Tub Heating: Scheduling That Saves

The mistake most spa owners make

The most common hot tub heating mistake is not the temperature you choose — it is the timing. Most owners either keep their spa at full temperature 24 hours a day, or they turn it on when they decide they want to use it and then wait an hour or more. Both approaches waste money.

Keeping a spa at 38°C constantly means paying peak electricity rates to heat water that no one is using. Heating on demand at the last minute means the heater runs at full load during the hours when electricity costs the most — typically weekday evenings between 17:00 and 21:00, which happen to be exactly when most people want to use their spa.

The solution is a pre-planned heating schedule that takes advantage of off-peak electricity rates available on most EU time-of-use tariffs.

How to build a simple off-peak schedule

A basic schedule works in three blocks:

1. Off-peak heating window — typically 23:00 to 06:00, or whatever hours your tariff designates as cheap. Program the spa to heat to its target temperature (e.g. 38°C) during this window.
2. Standby hold — from early morning until a couple of hours before you typically use the spa, drop the set point to 34°C to 35°C. The spa runs its circulation pump and holds at this modest temperature without consuming much heating energy.
3. Pre-warm — schedule a top-up two hours before your typical usage window. If you usually use the spa at 20:00, schedule a heat cycle from 18:00 to 20:00. This top-up is small because the spa is already close to temperature — and you avoid running the heater at the most expensive time of day.

For a typical German time-of-use tariff where off-peak rates are 30 to 40% lower than peak rates, this schedule alone typically cuts the heating portion of your electricity bill by 20 to 30% with no change in usage habits.

Where Spapilot fits

The schedule described above is technically possible to set on most modern spa control panels — but it requires navigating menu systems that many owners find unintuitive, and any change to routine requires repeating the process at the panel.

Spapilot replaces this with a simple weekly schedule builder in the app. You drag time blocks, set target temperatures for each block, define your off-peak hours once, and the system handles everything automatically. You can override any scheduled state from your phone at any time — for example, if your plans change and you want the spa ready at 19:00 instead of 20:00, a single tap adjusts that day without changing the rest of the schedule.

Owners typically set this up once and then forget about it, seeing the savings reflected in their electricity bill from the first month onwards.