Source
https://www.branz.co.nz/pubs/bulletins/bu689/ — original source (opens in a new tab; the file is not redistributed)
Summary
BRANZ Bulletin 689 (2024) is a plain-language overview of the domestic water-heating options available in New Zealand and how to choose between them. It is a taxonomy and comparison rather than a data study — it sets out the six main system families, their advantages and disadvantages, and the relative direction of their efficiency, emissions and operating cost, but carries no COP, cost or efficiency figures. For Neobiome Intelligence it consolidates the water-heating picture the wiki has built from CR_016 (solar thermal), CR_014 (heat pumps) and OT_038 (PV-direct + CO₂ heat pump): it confirms water heating is about a third of home energy, ranks the low-emissions options, and names dedicated-PV and wetback as recognised NZ types.
Key claims
- claim: "The main domestic water-heating system types in NZ are: electric (storage and continuous), fossil gas (storage and continuous/califont), heat pump (air-to-water or ground-to-water), thermal solar (with electric back-up), dedicated photovoltaic (with electric back-up), and wetback connected to a solid-fuel burner (with electric back-up)."
source_location: "§1.0.2 (p.1)"
- claim: "Water heating accounts for approximately one-third of the energy use in a typical NZ home on average."
source_location: "§1.0.1 (p.1)"
- claim: "On operating greenhouse-gas emissions, heat pumps, dedicated photovoltaic and thermal solar systems are lowest, while fossil gas systems are comparatively highest. Electric resistance has lower emissions than fossil gas because NZ grid electricity is already largely renewable (with plans to move closer to 100% renewable), but has higher operational cost than heat pumps, thermal solar or PV systems and contributes to peak electricity demand (which can be avoided using ripple control where offered)."
source_location: "§1.0.9, §2.1.3–2.1.4 (pp.1–2)"
- claim: "Heat-pump water heaters mostly transfer heat from the air (air-to-water); ground-to-water heat pumps draw on a less-variable ~12°C source, making them more efficient than some air-to-water units. Heat pumps using CO₂ as the refrigerant avoid high-global-warming-potential synthetic refrigerants — a typical synthetic refrigerant has a GWP around 1,430 times that of CO₂, and systems lose around 6% of their refrigerant per year."
source_location: "§2.2.1–2.2.4 (pp.2–3)"
- claim: "Electric storage water heaters were historically the dominant type, but sales of continuous-flow gas (califont) systems have grown (EECA sales data). Installing water-efficient fixtures and appliances (efficient showerheads, washing machines, dishwashers — many with water/energy star ratings) reduces hot-water demand and so the energy needed to heat it."
source_location: "§1.0.3, §1.0.8 (p.1); Figure 1"Neobiome Intelligence relevance
- D01 — water-heating taxonomy & emissions ranking. Bulletin 689 consolidates the full NZ water-heating option set and ranks operating emissions (heat pump / dedicated PV / thermal solar lowest; fossil gas highest) — the framing that situates the wiki’s individual sources: solar thermal (CR_016), heat pumps (CR_014), and the PV-direct + CO₂ heat-pump performance (OT_038) OT_041.
- Third independent confirmation of the hot-water load. Water heating ≈ ⅓ of home energy here, ~31% in SR488, 29% in HEEP — three NZ sources converging on hot water as a dominant demand the self-sufficiency design must serve OT_041.
- Heat-pump refinement (with CR_014). Ground-source > air-source efficiency (steady ~12°C source) and the CO₂-vs-synthetic refrigerant GWP point add an embodied-emissions nuance to the heat-pump cost/COP picture OT_041.
- ⚠ Scope: qualitative overview — no COP, cost or efficiency figures, so it fills no model cell; the COP/cost cells stay with CR_014 / OT_038 (RT_210) and solar-thermal with CR_016.
Research targets
Research gaps
- A NZ comparison table of water-heating systems with quantified lifetime cost, efficiency/COP and operating emissions (Bulletin 689 gives only the qualitative ranking) — would let the model rank heat-supply options on cost-emissions rather than direction alone.
Connections
Links to
Referenced by
EDT domains (1): D01: Renewable Energy & Storage Systems
Sources (1): OT_052
Technologies (1): Solar-Direct PV Water Heating