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 quarter-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 prices, one per 15 minutes, are published around 13:00.
- Quarter-hour price
- The electricity price per 15-minute period instead of per hour. The day-ahead spot price has been set at 15-minute resolution since October 2025, giving 96 prices per day. Gives price control more and finer moments to choose between.
- Price control
- Automatically controlling a heat pump by the electricity price so heat is produced when power is cheapest. Needs an electricity contract that follows the spot price, and works because the house stores heat.
- Hourly price
- An electricity price that follows the spot price hour by hour. The spot price was set per hour until October 2025 and is now set per 15 minutes (see Quarter-hour price), but many people still say hourly price. An hourly-price contract charges the average spot price for each hour, unlike a fixed price or a monthly variable price.
- Smart control
- Umbrella term for systems that shift electricity consumption between expensive and cheap periods to exploit price variations. For heat pumps it’s the single biggest saving available without replacing equipment.
- Spot price
- The variable electricity price set by Nord Pool, per 15 minutes since October 2025 (previously per hour). Different from fixed and rolling monthly prices in that it has 96 prices 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
- Older, everyday name for an electricity contract that follows the Nord Pool spot price. The spot price has been set per 15 minutes since October 2025, so such a contract now has either a quarter-hourly price or an hourly price (an average per hour). A prerequisite for smart control — without a contract that follows the spot price 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. Support via Home Assistant is in development in Therilly.