Daikin Altherma H Hybrid: heat pump and gas boiler hybrid explained

A Daikin Altherma H Hybrid is two heat sources in one heating system: an electric air source heat pump outdoors and a gas boiler, either the one already in the house or a new one, working under a single control¹. Daikin describes it as a way to upgrade an existing gas boiler with an energy-efficient hybrid heat pump, and as a combination of gas and renewable energy¹.

The appeal is that it does not ask a household to abandon a working boiler or replace every radiator. Daikin states the Altherma H Hybrid can easily connect to existing piping and radiators and connects to existing gas piping for easy, fast installation¹. There is also an outdoor-unit-only option: fitting the heat pump alone and combining it with the boiler already in place, which Daikin describes as a cheaper and easier start into renewable energy¹.

What it does not do is take a home off gas. The boiler stays, the gas connection stays, and the system switches between the two depending on conditions and running costs. For a household weighing energy independence, that is the trade: less gas burned, but not no gas, and a new dependence on a manufacturer's control system and app.

Three operating modes: heat pump, hybrid and gas

Daikin states the system has three types of operations⁴. In heat pump operation it describes the heat pump as the best available technology for optimising running costs at moderate outdoor temperatures. In hybrid operation both the gas boiler and the heat pump run simultaneously, which Daikin frames as delivering the ultimate comfort for the home. In gas operation, when outdoor temperatures fall drastically, the unit automatically switches to gas mode⁴.

The product pages put the same idea more briefly: the system switches between heat pump only, heat and gas combined, or gas only, to keep efficiency high and costs low⁵. That is the whole design. The heat pump carries the milder part of the year, the boiler carries the coldest days and the peaks, and the two can run together when demand is high.

Independent guidance describes the same architecture in slightly different terms. The HHIC views a hybrid heat pump as an electric-driven air source heat pump combined with a new or existing gas condensing boiler alongside a single control that operates the full system². SGN describes a hybrid system as using intelligent controls to determine the most efficient way to heat a home⁶, and Cadent states the system automatically chooses the most efficient and cost-effective way to heat your home⁷.

The practical consequence is that the household keeps two fuels and two sets of running costs. The heat pump runs on electricity, the boiler on gas, and the split between them over a year depends on the weather where the house is and on the price gap between the two fuels at the time. Nobody can state in advance what proportion of a given home's heat will come from the heat pump.

How the system decides when to use gas and when to use electricity

Daikin states the system determines the most energy-efficient combination based on energy prices, outdoor temperatures and indoor heat requirement⁴. The hybrid product pages give the same three inputs: the prices of electricity and gas and the outdoor temperature⁵. The decision is made by the controls, not by the householder.

Independent sources describe the mechanism in the same way. Cadent states the system automatically chooses the most efficient and cost-effective way to heat your home⁷. OFTEC notes that typically the manufacturer of the system components provides a dedicated control system capable of determining the best technology to use depending on preprogrammed parameters such as temperatures, unit cost of energy and equipment performance⁸. The HHIC describes the existing heat generator being replaced with a hybrid heat pump and intelligent control, with hot water supplied by the boiler and the boiler supporting the system during cold periods².

That last point matters for how the system behaves day to day. Hot water is the boiler's job in the configuration the HHIC describes, and the boiler also backs up the heat pump when it is cold. So the gas side of a hybrid is not a rarely used fallback; it is doing real work across the year.

Daikin's own smart control layer goes further on the electricity side. The Altherma UP series is described as learning how and when a household uses energy, predicting future consumption and factoring in local weather forecasts to plan ahead, with a fully automated service using AI and occupancy detection to optimise performance, cut running costs and reduce carbon⁹. Daikin also states its heat pumps use smart algorithms to analyse a household's energy usage, identifying peak demand periods and lower demand periods to maximise solar self-consumption¹¹.

Specifications: outputs, temperatures, sound and energy label

The Altherma H Hybrid carries an energy label for heating of up to A++ on the A+++ to D scale¹. That is a step below the A+++ that Daikin lists for several of its full heat pump ranges, including the Altherma 4 H F, the Altherma 3 H MT F, the Altherma 3 H HT F, the Altherma 3 R F and the Altherma 4 H W¹². The gap reflects the boiler in the system: a hybrid's overall label is not the same as a heat pump running alone.

Official guidance published in November 2016 lists the Daikin Altherma Hybrid at a rated output of 5 or 8 kW, with an SSHEE range of 127 to 129 at 55 °C under average climate conditions¹⁷. That document also states that a hybrid heat pump system can meet the full heating and hot water needs of a domestic property¹⁷.

The indoor unit is compact enough that Daikin states it can even fit in cupboards¹. The outdoor unit can be installed anywhere, including on the terrace, in the garden, or on the building's roof or exterior⁵.

Fitting it to an existing home: piping, radiators and the outdoor-unit-only option

The hybrid route is built around not disturbing what is already there. Daikin states the Altherma H Hybrid can easily connect to existing piping and radiators, and that its compact design requires minimal space and integrates with existing piping and radiators¹. The Altherma Hybrid heat pump page adds that it can be integrated with existing radiators, or installed with new low-temperature heat convectors¹⁸.

On emitters, Daikin states the Altherma H Hybrid connects directly to various heating and cooling emitters including underfloor heating, heat pump convectors or high- or low-temperature radiators¹. Underfloor heating is not a requirement for a heat pump, and Daikin notes radiators work very well with modern heat pump systems too¹⁹. Where underfloor heating is fitted, Daikin describes combining it with a heat pump to keep rooms warm in winter and provide gentle cooling in summer²⁰. Daikin heat pump convectors work similarly to a radiator but can be used for both heating and cooling a room, and Daikin states they can be paired with all its air-to-water heat pumps and hybrid heat pumps²⁰.

The outdoor-unit-only option is the cheapest entry point. Daikin describes choosing to install the outdoor unit only and combine it with the existing boiler as a cheaper and easier start into renewable energy¹. The outdoor unit itself can go on the terrace, in the garden, or on the building's roof or exterior⁵.

Daikin states a hybrid heat pump can be suitable for a variety of houses, including new builds, apartments, renovations, or existing properties for boiler replacement⁵. The company's own readiness check tells a householder whether their home is suitable, and where it is, states: "Congratulations! Your home is ready for a Daikin Altherma hybrid heat pump."¹⁸

Hot water: tank sizes and temperatures up to 65 °C

The Altherma H Hybrid provides heating and hot water, and Daikin lists domestic hot water temperature up to 65 °C¹. The domestic hot water tank is optional and available from 150 to 300 litres to suit any home¹. The same 65 °C figure appears across the wider Altherma range, including the Altherma 4 H F, the Altherma 3 H HT F, the Altherma 3 H MT F, the Altherma 3 H MT W, the Altherma 3 H HT W and the Altherma 4 H W¹².

Tank capacity varies by model. The Altherma 3 H HT F is listed with a combined stainless steel domestic hot water tank of 180 or 230 litres and a heat pump for easy installation²³. The Altherma 3 H HT W lists an optional tank available from 150L to 300L²². The Altherma 3 R F is listed at 180 litres²⁴. The Altherma 4 H W pairs with a separate water tank¹⁶.

The Altherma H Hybrid also offers an optional thermal store, which Daikin states maximises energy usage and connects to additional heat sources¹. That is the component that would let a household bring in something beyond the heat pump and boiler, such as a solar thermal input or a heat battery, though Daikin's own description stops at connecting to additional heat sources.

Smart control with the Onecta app and voice assistants

Daikin lists smart control for the Altherma H Hybrid via the Onecta app, Google Assistant and Amazon Alexa¹. The app allows a householder to manage the unit from anywhere using a phone or tablet, create schedules and track usage¹. The same combination appears across the Altherma range, including the Altherma 3 H HT F, the Altherma 3 H HT W, the Altherma 3 H MT F, the Altherma 3 R F, the Altherma 4 H W, the Altherma 4 H F, the Altherma 3 H MT W, the Altherma 3 R MT F and the Altherma 3 R MT W¹². The Altherma 4 is described as connecting with the Onecta app, Google Assistant or Amazon Alexa for voice-activated or remote system management²⁷. On one Altherma 3 H HT F product page the Onecta app is listed as optional²³.

This is where a hybrid creates a dependence that a plain boiler does not. Local control at the unit continues without an internet connection, but remote scheduling, usage tracking and voice control run through a home broadband connection, Daikin's app and Daikin's servers. If the app is discontinued or the connection drops, the heating still works; the remote layer does not.

Daikin's wider control range includes the Altherma UP series, described as a fully automated service using AI and occupancy detection to optimise performance, cut running costs and reduce carbon, learning how and when a household uses energy and factoring in local weather forecasts⁹. Daikin also states its heat pumps use smart algorithms to analyse household energy usage to maximise solar self-consumption¹¹. Those functions sit on top of the hybrid's own fuel-switching logic, not instead of it.

What owning a hybrid means for household energy independence

A hybrid is a partial step, and it is worth being clear about which part. The heat pump runs on electricity, so a household with solar panels can cover some of its heating from its own roof, and Daikin states its heat pumps use smart algorithms to analyse household energy usage to maximise solar self-consumption¹¹. Daikin also describes an experiment using an Altherma heat pump with a 250-litre hot water tank connected to photovoltaic panels¹¹.

But the boiler remains, and with it the gas connection and a gas supplier. Daikin's own full heat pump pages make the contrast explicit: the Altherma 3 R F is described as having no gas dependency and utilising renewable energy²⁴, and the Altherma 3 H HT F as having no gas dependency¹². The hybrid pages make no such claim. A household on a hybrid is still on the gas grid, still exposed to gas prices, and still dependent on a gas supply for the coldest part of the year and, in the HHIC's configuration, for hot water².

The evidence on how hybrids perform in real homes is thinner than for full heat pumps, and older. The National Energy Action case study CP747 covered the installation of Daikin Altherma hybrid heat pumps in 24 properties, and set out to examine the impact on residents' comfort and satisfaction levels²⁸. A later NEA study, CP759, aimed to establish the running costs of the Daikin Altherma hybrid heat pump compared with replaced gas boilers, examine the impact on residents' comfort, examine whether residents could control the system effectively, and establish how performance is affected when retaining existing radiators, including SCOP and the ratio of heat provided by the gas boiler and the air source heat pump. It also set out to determine whether a hybrid heating system is a cost effective replacement for housing associations carrying out boiler renewals²⁵. Those are the questions a householder would ask, and the study is dated 2018.

On the manufacturer side, Daikin has been expanding its UK presence. CIPHE reported Daikin adding four new centres²⁹, and a Heat Pump Keymark certificate dated 2025-09-29 covers Daikin Altherma 4 H W+F air/water heat pump models under registration number 011-1W0930²⁷. Daikin states that smart programming saves 35% more energy than a traditional condensing boiler, by automatically determining the most energy-efficient combination⁴. That is a maker's figure for its own system, not an independent measurement.

The honest summary for a household is this: a hybrid cuts gas use without a full conversion, keeps the existing radiators and pipework, and adds an electricity demand that solar panels can partly offset. It does not end gas dependence, it adds a dependence on a manufacturer's control logic and app, and the independent evidence on running costs in UK homes is old and small. For households where a full heat pump is not practical yet, that is the trade on offer.