Source
https://homesforgenerations.goodhomes.co.nz/reports_and_papers/riggs-l-isaacs-n-and-v-white-2023-examining-the-factors-affecting-household-energy-expenditure-report-for-building-better-homes-towns-and-cities-affordable-housing-for-generations/ — original source (opens in a new tab; the file is not redistributed)
Riggs, Isaacs & White — Factors affecting Household Energy Expenditures (OT_106)
RT_324 target — a MODERN, MODELLED NZ space-heat datapoint for
heat_space_kwh_hhA 2023 physics-first bottom-up estimate: a Wellington (Kelburn) dwelling needs 2,663 kWh/yr of space heating and 2,951 kWh/yr of water heating under a full-comfort NZBC regime (whole-house 20 °C, 1 ACH, 184 heating days). This is a demand figure, not measured consumption — it validates a modernisation discount on the 2005-vintage HEEP empirical baseline (OT_037), but must not be read as what a spot-heating NZ household actually burns.
Summary
BBHTC/BRANZ working paper (March 2023) examining what drives New Zealand household energy expenditures. It combines two methods. Section 3 builds a physics-first bottom-up model comparing space (internal-air) heating to domestic hot-water (DHW) heating for a single standardised Wellington/Kelburn dwelling, to show that seasonal energy variation is driven overwhelmingly by space heating, not water heating. Sections 4–6 run a weighted generalised linear model (GLM) on Household Economic Survey (HES) expenditure microdata (survey years 2006/07, 2009/10, 2012/13, 2015/16, 2018/19) accessed through the Stats NZ Integrated Data Infrastructure (IDI), to quantify how dwelling characteristics, tenure, region, interview month and income affect actual annual energy spend. Its NI value is threefold: the modelled space-heat kWh (D01/D04 calibration), the dwelling-form and size drivers of heating energy (D04), and the NZ household energy-expenditure baseline (I01).
Key claims
- claim: "SPACE-HEATING DEMAND — THE RT_324 TARGET (Section 3, verbatim). Annual average internal-air (space) heating energy for a Wellington/Kelburn dwelling = (7.4 C)*(240 m3/hr)*(24 hr/day)*(184 day/yr)*(1.15 kgm-3)*(1063 J C-1 kg-1) = 2,663 kWh/yr. Assumptions: house 10 m x 10 m x 2.4 m (240 m3), 1 air change per hour, heated to 20 C indoors; 184 heating days (months averaging < 15 C, May-October); heating-month average outdoor temp 12.6 C (Kelburn normals 1909-1980), giving deltaT 7.4 C. NZBC Clause H1 basis (continuous 20 C, min 1 ACH). This is a MODELLED full-comfort DEMAND figure, not measured consumption."
source_location: "Section 3 (Seasonality, Energy Use and Winter Heating), p.8-9; equation p.9 line 519-520"
- claim: "WATER-HEATING DEMAND (Section 3, verbatim). DHW temperature-raise energy = (46.3 C)*(50*2 l/day)*(1 kg/l)*(365 day/yr)*(4187 J C-1 kg-1)*(1 kWh/3.6 MJ) = 1,966 kWh/yr (2 adults x 50 L/day at 60 C from 13.7 C cold water). PLUS standing (cylinder) losses of 2.7 kWh/day for a C-grade 180-litre cylinder = 986 kWh/yr. TOTAL water heating = 2,951 kWh/yr. Standing-loss reference: A/B-grade = 2.2 kWh/day, C/D-grade = 2.7 kWh/day (HEEP, Isaacs et al. 2010, p.237)."
source_location: "Section 3, p.9"
- claim: "SPACE vs WATER HEATING — DAILY AVERAGES & SEASONALITY (Section 3, verbatim). Space heating 2,663 kWh/yr is 'on par with' water heating 2,951 kWh/yr; over a 365-day year this is 7.3 kWh/day (space) vs 8.1 kWh/day (water). Monthly range: air/space heating 340-552 kWh (+80% warmest-to-coldest heating month) vs DHW 212-266 kWh (+26%). Conclusion: 'increased energy expenditure in colder months is largely attributable to air heating and not to other energy uses' — space heat is strongly seasonal, water heat near-flat."
source_location: "Section 3, p.9; Table 1 & Figure 4, p.10"
- claim: "TABLE-1 ANNUAL VARIANT + DISCREPANCY NOTE (Table 1, verbatim). Summed from monthly values, Table 1 gives Air heating = 2,674 kWh/yr and DHW total = 2,951 kWh/yr (DHW water-raise alone 1,965 + heat loss 986). The paper flags: 'The Year total in this table is calculated from the sum of monthly values, which differ slightly from the values given in the text' — i.e. the text figure is 2,663 kWh and the monthly-sum figure is 2,674 kWh (rounding); use 2,663 as the headline."
source_location: "Table 1 (Internal Air & Water Heating Energy Use by Month), p.10"
- claim: "HEEP END-USE SPLIT (Section 3, verbatim, citing Isaacs et al. 2010). 'the two largest household energy end-uses involved heating - space heating at 34% and hot water heating at 29% of total energy use.' (Household Energy End-use Project, ~400 NZ houses monitored 1999-2005.)"
source_location: "Section 3, p.8"
- claim: "HEATING FUEL / TYPE MIX (Section 2, verbatim, from Census data). 2018 Census main heating TYPES: heat pumps 44% of households, electric heaters 41%, wood 31% (down from ~50% in 1986-96), coal ~1%. Electricity was 70-80% of main heating type 1996-2013. In 2013, ~75% of households used electricity in some combination for heating (electricity-only 36%, electricity+wood 17%). Bottled gas peaked at 28% (2001-06); mains gas steady 10-14% (1996-2018)."
source_location: "Section 2 (Overview of Heating in New Zealand), p.4-7; Figures 1-3"
- claim: "HOUSEHOLD ENERGY EXPENDITURE BASELINE (Table 2, verbatim, nominal NZD, HES-weighted). Total energy expenditure (no fees): all-months $2,314/yr, cold-months $2,573, low-income $2,012, smaller-homes $2,217. Total energy incl. supply charges: all-months $2,328, cold-months $2,589, low-income $2,026. Electricity alone: all-months $1,958, cold-months $2,169, low-income $1,757. Electricity is ~85% of total energy expenditure. Avg total HH income $65,259 (all) vs $37,943 (low-income)."
source_location: "Table 2 (Summary Statistics by Analysis Sample), p.14; electricity-85% note p.18/20"
- claim: "REGRESSION DRIVERS OF ENERGY SPEND (Table 4 / Section 6, verbatim, all-months GLM col 1 unless noted). Stand-alone home +$237/yr vs attached (greater exposed surface). Dwelling size: 1-2-room vs 9+-room = -$1,384/yr (all-months) / -$1,637 (cold-months); overall the 1-2 vs 9+ gap ranges $1,200-$1,700/yr. Auckland region -$204/yr (all-months) / -$271 (cold-months) vs rest of NZ. Income: a 1% income rise adds ~$3.50/yr (all-months), $4.36 (cold-months), $1.85-$2 (low-income) — non-linear. Cold months Jul-Sep +$500-$650/yr vs December; ~$50/month higher in coldest vs warmest months. Social housing +$160-$260/yr vs owner-occupier."
source_location: "Table 4 (GLM, Weighted), p.24-25; Section 6, p.21-28"
- claim: "RESIDENTIAL ELECTRICITY PRICE TREND (Appendix B, verbatim, MBIE). NZ average residential electricity price rose from 19 c/kWh in 2006 to 29 c/kWh in 2021, roughly +1 c/kWh per year to 2015 then flat 2015-2021 (< 1 c over the 6-year period). No extreme price shocks over the 2006-2019 analysis window."
source_location: "Appendix B, p.38; Figures B1-B2"Neobiome Intelligence relevance
Directly serves the RT_324 goal — a modern NZ calibration point for the model’s heat_space_kwh_hh parameter — plus two adjacent NI inputs.
- D01 / D04 — space-heat kWh (
heat_space_kwh_hh): the headline 2,663 kWh/yr is a 2023-published, physics-first bottom-up estimate for a temperate Wellington dwelling. It is the “modern” anchor the RT sought to validate the 0.843 modernisation discount (CR_051 / CR_015) applied to the 2005-vintage HEEP empirical baseline (OT_037). Critical caveat for the engine: this is a full-comfort DEMAND figure (whole-house 20 °C continuous, 1 ACH, NZBC H1 basis), and the paper itself documents that NZ households spot-heat and under-heat — so measured actual space-heat is materially lower than 2,663 kWh. Use 2,663 kWh as the design/demand value for a well-served dwelling; do not treat it as observed consumption. It is also location-specific (Kelburn/Wellington HDD, 184 heating days) and uses 1909-1980 climate normals, so “modern” means the method/publication, not a warming-adjusted climate — a warmer/colder region needs rescaling by heating-degree-days. - D04 — dwelling form & size drivers: empirical, NZ-specific support for compact, attached, well-insulated habitat design. A stand-alone dwelling costs ~
237/yr more energy than an attached one (surface-area/heat-loss physics), and a 9+-room dwelling ~1,200-1,700/yr more than a 1-2-room dwelling. This is the strongest NZ expenditure-based confirmation that dwelling size and detachment are first-order heating-energy drivers. - I01 — household energy OpEx baseline: an NZ-representative (HES/IDI-weighted) household energy bill of ~**
2,328/yr** (all-months) rising to ~2,589 in cold months, with electricity ≈85% of it, and a residential price of 19→29 c/kWh (2006→2021). These are direct NZ inputs for the model’s household energy-cost / OpEx line and for its electricity-tariff assumption.
Feeds d01_renewable_energy_storage, d04_sustainable_habitat_building, i01_financial_economic_sufficiency.
Research targets
Documents to retrieve
- None new. The upstream empirical baseline (HEEP, Isaacs et al. 2010) is already held as OT_037.
Research gaps
- RT_358 (gap): OT_106’s 2,663 kWh is a modelled full-comfort demand, not measured consumption. NI still lacks a post-2015 MEASURED NZ average space-heat actual-consumption figure (HEEP is 2005-vintage) to bound the gap between design demand and rationed real-world use — check for a BRANZ HEEP-successor / Warmer Kiwi Homes evaluation dataset.
Notes
Primary source, read verbatim (pdftotext -layout); data_quality: verified. Single-file PDF; authoritative BBHTC publication download (not AI-prepared), so no retrieval-provenance block. Two internal evidence types kept distinct in the claims: the Section-3 modelled space/water-heat physics (RT_324 target) and the Sections 4-6 HES-regression expenditure figures. ⚠ The 2,663 kWh (text) vs 2,674 kWh (Table 1 monthly-sum) discrepancy is the authors’ own rounding note — 2,663 is the headline. ⚠ Exact download URL to confirm; RT row cited buildingbetter.nz HES-energy-expenditures-report-Final-2023.pdf. Not formally peer-reviewed (BBHTC working paper) — but the space/water-heat calc is transparent first-principles physics and the regression uses official HES/IDI microdata.
Connections
Links to
EDT domains (2): D01: Renewable Energy & Storage Systems · D04: Sustainable Habitat & Building Technology
SSI indicators (1): I01: Financial & Economic Self-Sufficiency
Referenced by
EDT domains (2): D01: Renewable Energy & Storage Systems · D04: Sustainable Habitat & Building Technology
SSI indicators (1): I01: Financial & Economic Self-Sufficiency
Sources (1): OT_153