Reference
Glossary — heat pumps, electricity and smart control
A plain-language definition of every term we use in guides, comparisons and integration docs. Sorted alphabetically.
- AI heat pump control
- Software that controls a heat pump using data such as hourly spot prices, weather forecasts and the home’s thermal characteristics. Differs from simple time-of-day control by being dynamic and adaptive.
- Bivalent point
- The outdoor temperature at which an air-source heat pump switches to an electric element as a supplement. A lower bivalent point means a more efficient pump in cold climates.
- COP (Coefficient of Performance)
- The pump’s instantaneous efficiency — kWh of heat per kWh of electricity. A modern ground-source pump has a COP around 4 at 0 °C outside; an air-to-water pump around 3.
- Demand charge
- A charge based on the highest power (kW) a household draws within a month. Used by several Swedish grid operators (Ellevio, E.ON, etc.). It rewards smoother demand — exactly what smart heat pump control delivers.
- Electricity price area
- One of Sweden’s four zones set by Nord Pool: SE1 (Luleå), SE2 (Sundsvall), SE3 (Stockholm), SE4 (Malmö). Assigned by the grid operator and cannot be chosen.
- Flow temperature
- The temperature of the water leaving the heat pump for the radiators or underfloor heating. The single most important setpoint — lower flow temperature equals higher efficiency.
- Renewable electricity
- Electricity from wind, hydro, solar or biomass sources. When instantaneous generation is high, spot prices drop — that’s when smart control runs the heat pump hard.
- HAN port
- A standardised port on modern Swedish utility meters (all post-2024) that exposes real-time data. Compatible meters like the HomeWizard P1 can be plugged in without an electrician.
- Compressor
- The pump’s "heart" — drives the refrigeration cycle. Wear is minimised by avoiding short start/stops; long, smooth runs are gentlest.
- Comfort floor
- A user-defined minimum indoor temperature that smart control must never go below. Typically 20–21 °C for modern homes.
- MELCloud
- Mitsubishi Electric’s cloud API for remote control of Ecodan, Zubadan and similar pumps. The standard interface between third-party services like Therilly and the pump.
- Nord Pool
- The Nordic electricity exchange where the wholesale spot price is set each day. Next-day hourly prices are published at 13:00.
- Smart control
- Umbrella term for systems that shift electricity consumption between hours to exploit price variations. For heat pumps it’s the single biggest saving available without replacing equipment.
- Spot price
- The hourly variable electricity price set by Nord Pool. Different from fixed and rolling monthly prices in that it changes 24 times per day.
- Thermal inertia
- How long a home holds its temperature without added heat. Stone houses with underfloor heating have high inertia (hours); lightweight construction with forced air has low (minutes). Smart control exploits inertia to shift heating to cheaper hours.
- Tibber Pulse
- A small sensor that mounts on the meter’s optical interface and delivers second-by-second consumption data to Tibber and third parties. One of the easiest ways to get real-time metering.
- Hourly spot contract
- An electricity contract where you pay exactly the hourly Nord Pool spot price. A prerequisite for smart control — without hourly spot pricing there’s nothing to shift away from.
- Heating curve
- The relationship between outdoor temperature and the pump’s flow temperature. Typically tuned once a season; smart control sits on top of the heating curve rather than replacing it.
- Hot water cycle
- The pump’s periodic heating of the hot-water tank to a Legionella-safe temperature (~60 °C). Often profitable to shift to the cheap night hours.
- Wattnode
- A modular energy meter popular in Swedish housing associations and industry. Connects to Therilly via Home Assistant.