Source
https://github.com/rewiring-nz/household-model — original source (opens in a new tab; the file is not redistributed)
Rewiring Aotearoa (2024) — Household Model Methodology
The documented methodology behind OT_067/OT_029 — firms the NI demand-level lever + cross-checks a cluster of engine cells
The open-source methodology for Rewiring Aotearoa’s household energy model (github.com/rewiring-nz/household-model), citing government primaries (AU/NZ Residential Baseline Study 2021, MfE Warm Homes, EECA, MoT, AER). It documents the per-machine energy assumptions, the occupancy-based demand-scaling method the NI
demand_levellever needs, regional heat + solar factors, and battery/EV/emissions parameters — a transparent, government-sourced cross-check for several NI inputs. data_quality: verified.
Summary
The methodology document for Rewiring Aotearoa’s per-machine household energy/economics model — the engine underlying OT_067 (“Investing in Tomorrow”) and the EECA “Electric Homes” figures in OT_029. It sets out appliance energy use by machine and fuel (from the AU/NZ Residential Baseline Study 2021 + MfE + EECA + Frontier), regional heating multipliers, a non-linear occupancy-scaling method, vehicle energy + mileage tiers, regional solar capacity factors, and battery/solar/emissions logic. For Neobiome it is a cross-check goldmine: it firms the demand_level occupancy basis and corroborates the non-heat baseline, heat-pump COP, solar CF, and battery RTE.
Key claims
- claim: "Household energy does NOT scale linearly with occupancy; the model fits an exponential f(x)=a(1−e^(−b(x−1)))+c to AER 'Climate Zone 6' (NZ-analogue) electricity benchmarks and normalises to the NZ-average 2.7-occupant household. Resulting energy-consumption scaling factors (Table 2): 1 person 0.56; 2 person 0.90; 2.7 (reference) 1.00; 3 person 1.03; 4 person 1.07; 5+ person 1.37."
source_location: "§3.2 'Scaling appliance energy use by occupancy' Tables 1–2"
- claim: "Non-heating ('other') appliance electricity = 7.24 kWh/day at the 2.7-occupant reference ≈ 2,643 kWh/yr: other electronics (lights/laundry/IT/entertainment) 4.05 + other cooking (oven/microwave/refrigeration) 2.85 + space cooling 0.34. Per-machine energy (kWh/day): space heating — heat pump 2.3 (COP 4.08, EECA), electric resistance 9.39, gas/LPG 11.73, wood 14.44, diesel 12.95; water heating — heat pump 1.71 (367%), electric resistive 6.97, gas/LPG 6.6; cooktop — induction 0.75, electric resistive 0.83, gas/LPG 1.94. Appliance energy from the AU/NZ Residential Baseline Study 2021; space heating from MfE Warm Homes (2005)."
source_location: "§3.1 Appliances (tables 3.1.2–3.1.5)"
- claim: "Regional heating multipliers (national average = 1.0, from EECA air-conditioner data): Tasman 0.78, Nelson 0.78, Auckland 0.63, Northland 0.49, Waikato 1.06, Wellington 1.13, Marlborough 1.22, West Coast 1.45, Canterbury 1.56, Otago 1.60, Southland 1.76. Regional solar capacity factors (conservative static): Tasman 15.0%, Nelson 15.5%, Auckland 15.5%, Wellington 14.9%, Canterbury 14.3%, Otago/Southland 12.5%."
source_location: "§3.1.2 (heating multipliers) + §3.4 Solar (capacity factors)"
- claim: "Vehicle energy use: petrol 31.4, diesel 22.8, electric 7.324 kWh/day at the NZ-average mileage of 210 km/week (10,950 km/yr, MoT 2019); scaled by stated mileage. Usage tiers: low <100 (modelled 50), medium 100–300 (210 = national avg), high 300+ (400) km/week. So an EV at average mileage ≈ 2,673 kWh/yr, rising to ~5,000 kWh/yr at high (400 km/wk) mileage."
source_location: "§3.3 Vehicles"
- claim: "Battery: round-trip efficiency 0.95 (5% electronics/wiring losses), 1 cycle/day, 15-yr life, 85.22% average degraded performance; the model does NOT handle battery-without-solar (no arbitrage). Solar: 0.5%/yr degradation over 30 yr (93.08% average performance); 50% self-consumption assumed for both appliance and vehicle electricity. Emissions factors (MfE 2023, kgCO₂e/kWh): electricity 0.074, natural gas 0.201, LPG 0.219, wood 0.016, petrol 0.258, diesel 0.253."
source_location: "§3.4 Solar + §3.5 Battery + §4 Emissions"Neobiome Intelligence relevance
A transparent, government-sourced cross-check for a cluster of NI inputs — most importantly it gives the demand_level lever a real source. The occupancy scaling factors (1→0.56, 2→0.90, 2.7→1.00, 5+→1.37) validate the NI multipliers almost exactly: typical 1.00 = the 2.7-occupant reference, frugal 0.70 ≈ a 1.5–2-person household (between 0.56 and 0.90), and high should be ~1.37 (the 5+ value) rather than 1.35. So the model can re-source demand_level from this (occupancy-driven, no longer “assumed”) — confirming the lever’s design that demand scales on occupancy/appliance intensity, not electrification. Corroborations: non-heat baseline 7.24 kWh/day ≈ 2,643 kWh/yr (the model’s elec_nonheat_hh 2,680 holds); solar CF Tasman 15% ≈ 1,314 kWh/kWp/yr (consistent with RD_013’s ~1,389); battery RTE 0.95 (vs the model’s 0.90 — RA is more optimistic); heat-pump COP 4.08 (vs the model’s conservative cop_air 3.5); EV energy ~2,673 kWh/yr at average mileage (so the model’s ev_kwh_per_ev 4,000 corresponds to above-average ~310 km/wk driving — defensible, but reconcile). Advances RT_237 (the demand-scaling method; the underlying AU/NZ Residential Baseline Study 2021 is the next ingest) and RT_222 (battery RTE). Recommendation (deferred to after the Excel review): re-source demand_level to OT_070, values frugal 0.70 / typical 1.00 / high 1.37.
Research targets
Research gaps
- RT_237 (advanced): this source is the method (occupancy scaling) + per-machine energy; the underlying appliance dataset is the AU/NZ Residential Baseline Study 2021 (staged for the next ingest), which closes it.
- RT_222 (advanced): RA uses battery RTE 0.95 (vs the model’s 0.90) — a second NZ-context datapoint; the gap (a measured NZ round-trip efficiency incl. DoD/degradation) remains.
Connections
Links to
Referenced by
Sources (4): OT_071 · OT_072 · OT_153 · RD_020
EDT domains (2): D01: Renewable Energy & Storage Systems · D05: Smart Mobility & Electrified Transport