Case study: How one Plymouth household cut bills and carbon with a smart home energy system

When Andrew and his wife moved into a modern four-bedroom house in Plymouth, it featured four bedrooms, an Energy Performance Certificate (EPC) rating of 83 (B) and came with a standard gas boiler and radiators for heating. Despite this, they decided to take gas out of the equation altogether. By combining an air source heat pump, solar panels and home batteries, they’ve created a reliable ‘green energy’ system that keeps the house warm, cuts running costs and removes their dependence on gas. While their priority was doing their bit for the planet, the project shows what’s possible for able-to-pay households in the city.

Key objectives:

• Maintain comfort – keeping the home at about 20C all year round using the existing radiators as far as possible.
• Reduce overall energy use while maintaining their usual lifestyle.
• Using local energy sources to remove reliance on gas supplies subject to volatile global energy markets and associated price hikes.
• Play a small but real part in tackling climate change by moving away from fossil fuels.
• Stop using gas sources altogether and remove the gas meter.
• Gather robust data to understand performance and share learning with others, including Plymouth Energy Community and Climate Connections.

This was not about saving money, Andrew said, “We did not invest in this system to save money, it was driven by a desire to play a small part in the battle against climate change.”

The challenge:

Physical constraints
A small garden in an old quarry, which ruled out a ground source heat pump, these systems usually need space for long underground pipes or boreholes.

Finding the right installer
It was easy to find firms that only installed solar panels or only installed heat pumps, but harder to find one that could design and deliver a joined-up system including heat pump, panels and batteries.

Technical suitability of the home
There is often concern that older radiator systems may not work well with lower-temperature heating from heat pumps and might need costly upgrades or underfloor heating. The couple wanted to avoid major disruption if possible.

Complex tariffs and changing prices
The project began before the full energy price crisis triggered by the war in Ukraine, and tariffs changed several times during the period of evaluation, making before and after cost comparisons tricky.

The solution: choosing a whole-house system

Andrew chose a contractor that not only acted as a main coordinator, but handled all the documentation and certification, so the system met recognised standards and qualified for available subsidies. The coordinator worked with a specialist subcontractor providing the technical design and installation.

Before installation, the house was surveyed to check:

• Heat loss and radiator sizes
• Positioning for the heat pump unit
• Suitability for extra solar panels and batterie

The radiators were deemed suitable without major upgrades, although a new hot water cylinder optimised for lower-temperature heat pumps was required.

Technical details

Andrew’s home uses a combination of a heat pump, solar panels, a hot water cylinder and home batteries that work together as one smart, low-carbon system. The solar panels generate electricity, which can power the home, charge batteries for later use, support the heat pump in heating or hot water and send any spare electricity back to the grid.

The heat pump replaces the old gas boiler and provides all the heating and hot water, with the hot water cylinder working efficiently for this lower-temperature system. Battery storage means sunny-day energy is kept in the home rather than imported from the grid.

Smart controls

The system is easy to monitor and control, helping the couple understand how energy is being used throughout the day.

• A simple app for the heat pump shows temperatures and how much energy is being used for heating and hot water.
• Another app for the solar and battery system displays how much electricity is being generated, stored or exported.
• A wi-fi thermostat can be placed anywhere in the house, keeping the temperature consistent at 20 degrees.
• A ‘holiday mode’ reduces energy use automatically when the house is empty.

Together, these features help the whole system run efficiently and reliably while making the most of the clean energy produced on site.

Key benefits

Comfort and reliability
The smart home system has efficiently kept the home at the target temperature of 20 degrees even throughout cold snaps and the winter months. The hot water temperature is more than adequate for showers and everyday use, with no intrusion from the air source heat pumps, disproving reports of noisy units.

Lower running costs
While the couple’s energy needs now all come from electricity, their detailed analysis shows:

• Annual electricity requirement is projected at about 4,163 kWh.
• Using the Government’s Energy Price Guarantee (EPG) tariff in October 2022, their 2025 gross energy cost was £1,001, with £361 back from exported energy to the grid.
• This compares favourably to the Government’s reference figure of £2,500 per year for an ‘average’ household under the same EPG.

Energy security
By removing their reliance on gas supplies, which is often exposed to volatile global markets and sudden price increases, the couple have strengthened their long‑term energy security. Combined with locally generated solar power, Andrew’s smart home system is far more resilient to future energy disruptions and wider global changes.

Climate impact
The most important benefit for Andrew is that his home now uses no gas at all and makes much better use of locally generated solar power. The couple have successfully removed direct fossil fuels for hybrid vehicle charging, heating, hot water and cooking, while the solar power is either used in the home, stored in batteries or exported to the grid.

Return on investment (ROI)

The total capital cost of the system, including heat pump, solar, batteries, installation and VAT, was about £27,000.

In return, the couple receive quarterly payments of about £295 for seven years under the Domestic Renewable Heat Incentive, which has since closed to new applicants and has been replaced with the Boiler Upgrade Scheme.

They also receive a small income from exported electricity under the Smart Export Guarantee (SEG), around 3p per kWh exported during the study period.

However, Andrew has deliberately not tried to calculate a simple payback period. For him, the main return is knowing that his home no longer relies on gas, contributes to wider climate goals and proves that a Plymouth home can run comfortably and reliably on a smart, mostly renewable system.

That said, his analysis suggests that the running costs are at least competitive with, and often better than, the old gas-based system, especially during the summer.

What’s next?

Andrew sees this project as a strong base, not the destination.

Andrew is looking at possible future improvements, including adding more solar panels if roof space and regulations allow, increasing battery storage to use more solar power on site and exploring solar thermal for hot water.

Case studies like Andrews’ show how individual households can make a real difference, especially those able to invest and want to be early adopters, helping to pave the way for others.