Case Study: Gas Boiler to Air to Water heatpump changeover

Project Overview

Location: Upper Hutt, Wellington

Home type: 230SQM built 2016 fully insulated and double glazed

Current System type: Baxi Duo Tec Compact boiler with Baxi 300L hot water cylinder servicing 2 large bathrooms and a hot water ring main pump, 12 radiators, 2 towel rails and Underfloor (Variocomp) heating to tiled kitchen, ensuite, bathroom and WC.

Project Overview: The homeowners wanted to move away from gas while retaining the comfort and efficiency of their existing hydronic heating system.

Their goal was to future-proof the home, reduce reliance on fossil fuels, and continue enjoying the even, comfortable warmth that hydronic heating provides.

🔍The Clients Challenge

The client had experienced an increase in gas pricing in late 2025.

Gas price Per KWh increase from 9.62 to 13.8 cents a 43.45% price increase.

Daily line change increase from 211.13 to 259.14 cents per day a 22% price increase.

Based on their 2025 gas usage they would be looking at increase on their gas bill of $1847.23 for just 2026.

🌟 The Vision

The  homeowners wanted to future-proof their home by reducing reliance on fossil fuels and increasing the use of renewable energy.

As part of the project, they chose to replace their existing gas boiler with a high-efficiency air-to-water heat pump while simultaneously investing in a solar photovoltaic (PV) system.

The combination of solar generation and heat pump technology allows the home to utilise renewable electricity generated on-site to help power both the heating system and other household electrical loads.

By combining solar generation with heat pump technology, the homeowners have positioned themselves to maximise the use of renewable energy while reducing operating costs and reliance on gas.

🌞 + 🔋 Renewable Energy Working Together

Heat pumps are one of the most efficient forms of home heating available, extracting renewable heat energy from the outdoor air and transferring it into the home. When paired with solar PV, the system becomes even more effective, allowing a portion of the electricity required to operate the heat pump to be generated on-site.

This creates a highly efficient heating solution that supports the homeowners' goal of reducing carbon emissions while maintaining the superior comfort of hydronic heating.

🏡 Pipeline's Solution

Pipeline designed and installed a complete heat pump-based hydronic heating solution featuring:

• Stiebel Eltron Trend 10.2 Air-to-Water Heat Pump
• HSBC Cool Cylinder
• Existing hydronic radiator and variocomp system retained and integrated
• New control and system management components
• Commissioning and optimisation of the complete system

The Stiebel Eltron Trend 10.2 was selected for its ability to efficiently produce the water temperatures required for hydronic heating while delivering excellent seasonal efficiency.

The HSBC Cool 300L Hot WaterCylinder was incorporated to provide the homes hot water along with system buffering and ensure stable operation, helping the heat pump operate efficiently under varying heating demands.

Pipeline designed and installed a complete heat pump-based hydronic heating solution featuring:

• Stiebel Eltron Trend 10.2 Air-to-Water Heat Pump
• HSBC Cool Cylinder
• Existing hydronic radiator and variocomp system retained and integrated
• New control and system management components
• Commissioning and optimisation of the complete system

🔧 The Installation process

The project involved:

• Removal and safe decommissioning of the existing gas boiler
• Modifications to the plant room pipework
• Installation of the outdoor Stiebel Eltron heat pump unit
• Installation of the HSBC Cool Cylinder
• Integration with the existing radiator network
• Electrical and control connections
• System filling, commissioning, balancing and testing

Careful planning ensured minimal disruption to the household throughout the installation process.

📈 The Result

The completed project delivered:

✓ Removal of gas reliance for home heating

✓ Improved energy efficiency

✓ Renewable energy integration through solar generation

✓ Future-ready heating infrastructure

✓ Comfortable, even hydronic heating throughout the home

✓ Reduced household carbon footprint

The homeowners now benefit from a modern heating solution that combines the comfort of hydronic heating with the efficiency of heat pump technology and the renewable energy advantages of solar power.

Real world savings