Retrofit stories

Every explanation in the 3D experience is also available here, without needing to load or navigate the model.

• The house as it wasBuilt in 1874 as the second of a row of eight red-brick Coastguard cottages on the coast: thick walls, a slate roof, and gas for heating and hot water. Every other story here describes a change to this house.
• From the worst room to the warmestThis small rear extension used to contain the coldest and dampest room in the house. Insulating the roof, outside walls and floor, together with better moisture extraction, transformed it into the room the homeowner now describes as the warmest and least damp.
• Going gas-free with a heat pumpIn 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).
• Making power on the roof since 2012Eight solar panels, 1.96 kW in all, have sat on the south-facing front slope since February 2012, and ever since they have paid the household a Feed-in Tariff for every unit they generate: about £1,100 a year by the homeowner's account, roughly £15,000 so far, much of it reinvested in the house's other retrofit measures. In 2025 they made roughly 1,750 kWh, and a battery added in 2023 and 2024 can store power for later use. The household is also paid about £40 a year for the power the panels export.
• A new front door, and new windows to comeA composite front door has replaced a wooden one that kept warping in the coastal air. Double glazing is due to be fitted throughout the house but has not been fitted yet.
• Fitting an EV charger to a street-front wallA 7.2 kW charger on the front wall charged roughly 2,100 kWh into the household's car in 2025. Charged overnight on a cheap rate, the homeowner estimates a 125-mile round trip to London at about £3, against about £21 to £22 in a petrol or diesel car (an illustration, not a bill). Over 2025 charging the car would have cost about £270 at the house's average price per unit, or about £150 at the overnight rate, against about £1,200 of petrol for the same miles. The charger shares its wall with a broadband box, an isolator and a downpipe, which shows the practical side of fitting equipment to an older house.
• A battery to move energy from one time to anotherA 9 kWh battery at the back of the house stores energy so it can be used later than it was made. In winter it is filled overnight on cheap electricity; for the rest of the year the sun does more of the work.
• Insulating the loft and under the floorIn 2023 the loft was topped up with insulation and boarded, and the cavity under the ground floor was insulated. Neither can be seen from the rooms. The homeowner feels the house now holds its heat much better, though nothing has been measured.
• How this house comparesThe solar panels have paid this house a Feed-in Tariff since 2012, about £1,100 a year and roughly £15,000 so far, much of it reinvested in the other retrofit measures. In 2025 this house heated itself and made its hot water on about a ninth of the energy a typical home uses for gas, made about two-thirds of a typical home's electricity on its own roof, and ran an electric car on about a quarter of the carbon of the same miles in a petrol one. In money, the house's whole 2025 electricity bill was about £480, against about £2,950 for a typical home's gas and electricity plus the petrol for the same miles (an illustration). These are comparisons with national figures, not with this house before it changed.
• How it was paid forAfter the solar panels, the household has spent about £31,300 of its own money on the other retrofit measures (about £37,500 with the panels). Those measures now save roughly £2,500 a year in running costs against a typical home running one petrol car the same miles (an illustration), and the panels' Feed-in Tariff has paid roughly £15,000 since 2012. This page sets out what each measure cost, what it saves, and the tariff, each told once.

Guided tour

A suggested order for the stories, starting at the front door. In the 3D view the tour panel can take you to each stop; here, read them in order. Your place is remembered in this browser only.

1. The house as it wasStart in the street, facing the house: how it was built in 1874.
2. Making power on the roof since 2012Out in the street, look up at the roof: the solar panels.
3. Fitting an EV charger to a street-front wallOn the front wall: the EV charger, and the car parked in the street.
4. A new front door, and new windows to comeAt the front door: the new door, and the glazing still to come.
5. Insulating the loft and under the floorIn the living room: the insulation under the floor and in the loft above, which you cannot see.
6. From the worst room to the warmestThrough the house and into the bathroom extension at the back: the room that went from the coldest to the warmest.
7. Going gas-free with a heat pumpOut in the back yard: the heat pump.
8. A battery to move energy from one time to anotherBeside the back door: the battery and inverter, which tie the energy together.
9. How this house comparesBack inside, in the kitchen: how it all compares with a typical home.

Equipment in the house

What each piece of retrofit equipment in the 3D model is, and where to find it.

• Air-source heat pumpThe outdoor unit of the Daikin heat pump that heats the house and makes its hot water, with its lagged pipes and condensate pipe.Where: Outside, in front of the bathroom extension's rear wall.Read the story: Going gas-free with a heat pump
• Hot water cylinder cupboardA curved cupboard holding the heat pump's hot water cylinder, a buffer tank and an expansion vessel.Where: Inside the bathroom extension, against the side wall by the back door.Read the story: Going gas-free with a heat pump
• Solar panels (1.96 kW)Eight Hyundai 245 W panels in two rows of four, making electricity from daylight.Where: On the south-facing front slope of the roof, beside the chimney stack.Read the story: Making power on the roof since 2012
• Solar PV inverterTurns the panels' direct current into the alternating current the house uses.Where: In the loft, on the right-hand party-wall gable beside the chimney breast.Read the story: Making power on the roof since 2012
• Battery (9 kWh)Stores electricity so it can be used later; about 8 kWh of it is usable. It sits under an insulation blanket.Where: In the rear yard, against the main rear wall.Read the story: A battery to move energy from one time to another
• Battery inverterCharges the battery and sends its energy back to the house.Where: In the rear yard, on the main rear wall above the battery.Read the story: A battery to move energy from one time to another
• EV charger (7.2 kW)Charges the household's electric car. It has no cable of its own.Where: On the front wall, near the right-hand end, about a metre up.Read the story: Fitting an EV charger to a street-front wall
• Renault Zoe E-TechThe household's electric car, parked nose-first to the house where it charges.Where: On the street in front of the house.Read the story: Fitting an EV charger to a street-front wall
• Composite front doorA composite door fitted in February 2026, replacing a wooden one that kept warping in the coastal humidity. It opens outward and gives access to the enclosed porch.Where: The front of the house, on the street.Read the story: A new front door, and new windows to come
• CityFibre broadband boxA broadband connection. It is not part of the energy system.Where: On the front wall, below the EV charger.
• Electric cookerAn electric oven with an induction hob, fitted in 2023, replacing a gas oven. Once the heat pump was installed in early 2024, nothing in the house used gas, which is why the supply was disconnected.Where: In the kitchen, along the wall it shares with the living room.Read the story: Going gas-free with a heat pump
• RadiatorsThe radiators were all replaced when the heat pump was fitted in 2024. A heat pump runs its water cooler than a boiler, so these suit it better.Where: In the bathroom, kitchen, living room and all three bedrooms.Read the story: Going gas-free with a heat pump
• Log burnerUsed only on very special occasions when the house is full of visitors, and only then if the weather calls for it: it has to be very cold before it is lit.Where: In the living room, in the recess of the chimney breast on the right-hand wall.Read the story: The house as it was