Victorian Retrofit House

Going gas-free with a heat pump

In February 2024 an air-source heat pump replaced this house's gas combi boiler. With new radiators and an electric oven and induction hob, the gas supply was disconnected altogether. The installation started badly, with a month without heating or hot water, but day to day it "feels amazing". In 2025 its electricity would have cost about £150 at the house's average price per unit, against about £770 of gas for a median home (an illustration).

What changed

A gas combi boiler used to heat the house and make its hot water. Octopus Energy installed a Daikin heat pump in its place. The outdoor unit stands in front of the bathroom extension's rear wall; a hot water cylinder, a buffer tank and an expansion vessel are in a curved cupboard inside the extension. Every radiator was replaced at the same time, and the gas supply was disconnected. The gas oven had already gone in 2023, replaced by an electric oven; the hob is induction. The log burner in the living room is hardly ever used.

The rough start

The work began in January 2024. Only then did it emerge that the house's main electricity fuse was too small for a heat pump, and National Grid had to upgrade the supply, at no cost to the household. The house spent the whole of January without heating or hot water, and the heat pump was in service by February 2024. To make up for the delay, Octopus gave £350 of account credit and £350 of wood for the log burner.

What it cost

Octopus quoted £8,200, radiators included, and the UK government's Boiler Upgrade Scheme paid £7,500, leaving £700 to pay. Disconnecting the gas properly was a separate job, which meant digging a large trench outside the house, and cost £1,200: £1,900 in cash altogether. After the January delay Octopus gave £350 of account credit and £350 of wood, so the heat pump job itself effectively cost £0, although the cash was paid first and the disconnection was an extra cost. Grants and their rules differ between schemes, places and years, and the goodwill was a one-off, so this is one household's outcome, not a typical price. Much of the household's own money for its retrofit measures came from the solar panels' Feed-in Tariff, described in the solar story.

What it costs to run

In 2025 the heat pump used about 1,150 kWh of electricity for heating and hot water. What that cost depends on when it ran, which its app does not record, so these are three pricing examples, not a measured cost. At the 13p a unit that the house's whole electricity bill averaged out at, standing charge included, it would be about £150. If all of it had run on Intelligent Octopus Go's cheap overnight rate of 7p a unit it would be about £80, and if all of it had run at the day rate of about 28p, about £320. A median home in England and Wales used about 10,100 kWh of gas in 2023, which at 2025's price cap rates (about 6.5p a unit, plus a standing charge of about 31p a day) would cost about £770, and that gas also covers cooking. Even at the day rate the heat pump's electricity would cost less than half of that. This is an illustration of scale, not a before-and-after: no bills exist for this house's old boiler, and another house would differ. It counts running costs, not what the equipment cost, and no payback is claimed.

Living with it

It "feels amazing day to day" and gives "a lovely temperature to shower in". It is "quieter than next door's exhaust from their combi", and silent indoors: "a massive blessing compared to our old noisy combi". It has an annual service from Octopus Energy. Asked what would be done differently: nothing, "the heat pump is great".

Working with the solar panels and battery

The heat pump is not directly connected to the solar panels or the battery, but they work well together. In very cold weather it has sometimes used up the whole battery and then drawn from the grid. This winter the plan is to heat the house a little overnight, when grid electricity is cheaper, while charging the battery, to get more out of the battery and heat pump in the cold. That is a plan, not yet a result.

How it works

A heat pump moves heat from the outside air into the house, using electricity to do it, rather than burning fuel. That is why it can deliver several times as much heat as the electricity it uses: the manufacturer rates this unit, a Daikin EDLA06E2V3 with a heating capacity of 6.0 kW, at a COP (the heat delivered for each unit of electricity) of 4.85 under standard test conditions (7 °C outside air, 35 °C water). Real-world figures vary with the weather and the temperature the radiators run at, and none have been measured here. It is a "monobloc": all of the refrigerant (1.35 kg of R32) stays sealed in the outdoor unit, and only water pipes run into the house.

Radiators and hot water

Because a heat pump runs its water cooler than a boiler, radiators chosen for one are usually larger or more numerous. In this house the old radiators needed replacing anyway. The new ones are larger in the large bedroom, living room and bathroom, and much deeper in the kitchen, and they use the space better because they stand upright in good places. In the two smaller bedrooms they are about the same size. The hot water cylinder in the cupboard stands about 55 cm across and 127 cm tall and holds roughly 200 litres, an estimate from its size. The water is heated to 45 °C each morning, around 4 to 5 o'clock, and once a week to 60 °C, the usual precaution against Legionella bacteria.

Energy use

The Daikin app reports that the heat pump used about 583 kWh for space heating and 569 kWh for hot water in 2025, 1,152 kWh in all. These are estimates from the unit's own sensors, and the app itself says they may contain some inaccuracies. For context, the median home in England and Wales used about 10,100 kWh of gas in 2023 (DESNZ), so the heat pump's electricity is very roughly a ninth of that. That comparison is an indication only: a national median is not a similar house, gas figures include cooking, which the heat pump figures do not, and the COP above is a test figure. Two people live in the house, and the Octopus app showed 3,693 kWh of electricity taken from the grid in 2025, which includes charging the car and is not the house's total electricity use.

Carbon, roughly

At the UK government's 2025 factors, the heat pump's roughly 1,150 kWh of electricity in 2025 is about 200 kg of CO2e on the UK grid average (0.177 kg per kWh), and the roughly 10,100 kWh of gas the median home in England and Wales used in 2023 is about 1,850 kg (0.183 kg per kWh): about a ninth. It is an illustration, not a measurement. It compares this house's heat pump with a national median, not with this house's old boiler, which was never measured; the median's gas includes cooking; and any of the heat pump's electricity that came from the solar panels would make its figure lower. The battery's effect on carbon cannot be determined from the available data: it can charge from the panels or from the grid, the split is not recorded, and storing energy loses some of it.

Benefits

Limitations

References

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