Project partners:
Installation team – Mainly Energy and Mainly Gas and Plumbing
Supplier – Consolidated Energy
About the Project
The Suburban Homestead Project exists to prove that a typical, ageing suburban house can be transformed into an efficient, resilient, and genuinely self-sufficient home – without moving to a lifestyle block.
This report documents the first major electrification and efficiency upgrade carried out for the project: replacing a 25 to 30 year old, low pressure electric hot water cylinder with a modern Reclaim CO2 heat pump hot water system. It’s the first instalment in an ongoing series of monthly updates, tracking exactly how much energy and money Tim and Kate save by making the switch – using real, logged power data rather than manufacturer estimates.
Meeting Kate and Tim
The project began with a visit to Tim and Kate’s home, a classic 1970s build in Auckland, to understand how the household actually uses hot water day to day, rather than simply swapping in a new cylinder based on assumptions.
During the initial consultation, the focus was on building a full picture of the home and household, including:
- Daily hot water habits: showers, bath use, laundry and dishwasher cycles, and peak demand times.
- The existing system: a 110L simplex low pressure storage cylinder nearing the end of its serviceable life.
- Pain points, including slow recovery, limited storage, and the inefficiency of resistive electric element heating.
- Wider goals for the home, including future rooftop solar, battery storage, and broader electrification.
- Practical constraints, particularly reclaiming the internal hot water cupboard for storage.
What This Meant for System Selection: A straightforward like-for-like cylinder replacement would not serve Kate and Tim well long-term. Their hot water demand, appetite for solar integration, and desire to free up internal storage space all pointed toward a system that heats and stores water far more efficiently, sits outside the home, and is ready to work alongside solar generation.
Why the Reclaim CO2 Heat Pump Hot Water System
After weighing up the options against Tim and Kate’s brief, a Reclaim CO2 heat pump hot water system with a 250L storage tank was selected, to be installed outside the home. Reclaim Energy’s CO2 (R744) refrigerant heat pump technology stood out for several reasons:
- Major power savings: heat pump water heating uses a fraction of the electricity of a resistive element cylinder for the same hot water output.
- Increased storage: moving from a 110L cylinder to a 250L tank gives significantly more hot water buffer.
- Solar-ready via dry contact: once rooftop solar is installed, the system can prioritise heating hot water using excess solar generation.
- Freeing up internal space: relocating the cylinder outside hands the original hot water cupboard back to the household.
- Refrigerant choice: CO2 (R744) is a natural refrigerant with an extremely low global warming potential.
The Changeover: Installation Day
The installation involved decommissioning and removing the old internal low pressure cylinder, and installing the new Reclaim CO2 heat pump hot water system outside the home. Key elements included:
- Safe disconnection and removal of the 25 to 30 year old internal cylinder and its low pressure fittings.
- Reconfiguring the plumbing for a mains pressure, outdoor-mounted system, improving water pressure throughout the home.
- Positioning and installing the Reclaim unit and 250L tank outside.
- Electrical works including provision for the dry contact solar control input.
- Reinstating the power monitoring module onto the new circuit.
Measuring the real difference: a dedicated power monitoring module logged the old cylinder’s usage through July, then the same monitoring was fitted to the new Reclaim circuit for August – a back-to-back, month-on-month comparison drawn directly from the household’s own real usage pattern.
The Savings Report: July vs August
The chart below shows daily hot water energy consumption for both months side by side: July on the old 110L low pressure electric cylinder, against August on the new 250L Reclaim CO2 heat pump system. Two days sit noticeably lower than the rest of August – 1 and 27 August – genuine low-demand days where the tank was already at temperature, not monitoring gaps.
| Metric | July — Old Electric Cylinder | August — Reclaim CO2 HWHP |
|---|---|---|
| Total monthly energy use | 207.7 kWh | 73.8 kWh |
| Average daily use (all 31 days) | 6.70 kWh/day | 2.38 kWh/day |
| Average daily use (excl. install/handover days) | 6.70 kWh/day | 2.54 kWh/day* |
| Storage capacity | 110L | 250L |
| Lowest Single Day | 2.71 kWh | 0.02 kWh |
| Highest Single Day | 10.72 kWh | 4.20 kWh |
*1 August’s 24.68 Wh reading is the lowest of the month, a genuine low-demand day rather than a data or installation issue, and is included in full in all totals and averages above.
The Headline Result: Tim and Kate’s hot water energy use fell from 207.7 kWh in July to 73.8 kWh in August – a reduction of 133.8 kWh, or approximately 64%, month on month, while gaining more than double the hot water storage.
What This Costs in Real Dollars
Using Tim and Kate’s electricity rate of $0.4009 per kWh, the logged data converts directly into a real running cost for each system, no estimates required. On the old cylinder, daily hot water heating typically cost between $1.10 and $4.30. On the Reclaim CO2 HWHP, most days sit between $0.65 and $1.70 – and on the lowest-demand day of the month, the system cost just one cent to run.
| Cost Metric | July — Old Electric Cylinder | August — Reclaim CO2 HWHP |
|---|---|---|
| Total monthly cost | $83.25 | $29.60 |
| Average daily cost | $2.69 | $0.95 |
| Average weekly cost | $18.80 | $6.68 |
| Monthly $ saved | – | $53.65 (64.4%) |
Rate used: $0.4009/kWh, flat, applied consistently across both months for a like-for-like comparison.
Watching the Gap Grow: Cumulative Cost
By day 31, Tim and Kate’s old cylinder had cost them $83.25 to run hot water for the month, while the Reclaim system delivered the same household’s hot water for $29.60 – a gap of $53.65 in a single month.
Plotting the running cost day by day makes the difference easy to see build up in real time. The two lines start together on day one and steadily pull apart as the month goes on.
What It Adds Up To Over Time
Using the measured daily average cost from each month and holding the electricity rate flat, the same pattern of use projects forward into meaningful weekly, monthly, and annual savings. Held flat over ten years and ignoring future electricity price rises, that projects to more than $6,300 in avoided running costs from this single change – before factoring in the value of solar integration.
These are projections based on one real month of data on each system rather than a full year, so they should be read as a strong early indicator rather than a guarantee; seasonal hot water demand, weather, and household routines will all move the actual annual figure around. That is exactly what the ongoing monthly updates in this series are designed to confirm.
Looking Ahead: Solar and Ongoing Monthly Updates
This installation is one piece of a much bigger picture for Tim and Kate’s home. This report marks the first entry in an ongoing monthly series tracking real energy use and savings as further upgrades, including solar, are added to the home.
Solar-Ready
The Reclaim system’s dry contact input means hot water heating can be prioritised to run on excess solar generation once rooftop solar is installed.
September Update
September’s full month of data on the Reclaim CO2 HWHP, tracking how daily draw continues to match real household demand.
Recovery & Comfort
Early observations on hot water recovery time and comfort with the larger 250L tank.
Solar Rollout
Progress on the household’s rooftop solar plans, and how the dry contact solar integration will be configured once panels are live.
Follow the Suburban Homestead Project
Installation team: Mainly Energy and Mainly Gas & Plumbing. Supplier: Consolidated Energy. Data source: independent power monitoring module readings, logged in Wh at daily resolution – July (old low pressure electric cylinder) and August (Reclaim 250L CO2 HWHP).