5 Invercargill
A telephone survey of domestic heating methods and fuels for Invercargill was carried out by Digipoll in October 2004. This involved surveying 158 households within the 2001 census area unit (CAU) areas of:
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Survey details are shown in Table 5.1. The number of households for 2004 was estimated based on 2001 census data for occupied dwellings, extrapolated for 2004 based on Statistics New Zealand population projections. [New Zealand Statistics 2004, www.stats.govt.nz/] The latter suggest a population projection for Invercargill of -14% by 2021. [High, medium and low population projections were estimated by Statistics New Zealand. The value used is the medium population projection.]
Table 5.1: Summary survey data, Invercargill
5.1 Home heating methods and fuels
The Digipoll survey was used to collect information on home heating methods and fuels for Invercargill. These data were collected for the purpose of evaluating the impact of variations in heating methods on air quality in Invercargill, in particular the extent of change required to achieve the national environmental standard for PM10. This section presents the results of the home heating survey for Invercargill largely in tabular form, in the expectation that these results will be of value in other assessments (eg, emission inventory studies).
Tables 5.2 and 5.3 show domestic heating methods and fuels used for the main living areas in Invercargill houses, and seasonal variations in heating behaviour. The main methods of heating were multi-fuel burners (34% of households) and electricity (63%). Many households used more than one method of heating in their main living area.
As with Gore, the use of multi-fuel burners in Invercargill is high (at 34%) relative to the national average (8% of households). This is compensated to some degree by a lower use of wood burners (17% compared with a national average of around 38%), and is likely to relate to the accessibility of coal in the Southland region.
Table 5.2: Domestic home heating methods and fuels, Invercargill
Of the households using wood burners, multi-fuel burners, open fires and gas, a small proportion burn all year round. During January these households heat their homes on an average of four days per week for households using gas, seven days per week for households using wood burners, and three days per week for households using multi-fuel burners. Results for open fires are subject to significant uncertainty owing to the smaller number of respondents with this heating method.
The quantities of fuel used per day are typically much less during the summer months than during the winter (Table 5.4). The exception is open fires, which indicate higher results during the summer months. This is likely to occur because the summer results are based on a very small number of households, which in this case burn more during the summer than the average of all households burning during the winter. It is likely that these households burn more than the winter average during the winter months as well.
Table 5.3: Monthly variations in heating behaviour and fuel use, Invercargill
Table 5.4: Estimated daily fuel use, by season, Invercargill
5.2 Insulation, cost of heating, income, and house age and size
In addition to collecting data for the purpose of evaluating the impact of variations in heating methods on air quality, information was collected on a number of variables relevant to the Ministry for the Environment's Warm Homes Project. Relevant data for Invercargill are presented in this section.
Figure 5.1 shows that the proportion of households using gas systems that are properly flued in Invercargill is similar to the national average (26% in Invercargill compared with 28% in the national survey). The proportion of older (pre-1994) wood burners (26% of wood burners) is less than the national average of 43%.
The amount spent on heating for a winter month, by heating method, is shown in Table 5.5. In Invercargill, households heating using open fires and wood burners spend less per month (around $60) than those using other heating methods, on average. This is similar to the national average for these methods ($60). Households using gas and multi-fuel burners spend more per month on heating than the national average for these methods.
Figure 5.2 shows the average heating costs, home ownership, age of dwelling and number of bedrooms for households in Invercargill. Unlike the results for New Zealand as a whole, open fires are not present in new houses in Invercargill (Figure 5.2). One-bedroom houses are typically heated using electricity and six-bedroom houses typically use wood burners or electricity in their main living area. Pellet burners were only used in owner-occupied dwellings, with around 2% of houses using this method.
Figure 5.1: Distribution of flued versus unflued gas heating and age of wood burner, Invercargill
Text description of figure
There are two pie graphs. The first graph shows the distribution of flued and unflued gas heaters. Unflued gas makes up 74% of all gas heating and Flued gas makes up 26%.
The second graph is divided by the age of wood burners. Post-1999 wood burners make up 44%, 1994-99 wood burners make up 30% and the remaining 26% of wood burner are Pre-1994.
Table 5.5: Average monthly heating costs (winter), Invercargill
Figure 5.2: Domestic heating method, by average monthly heating expenditure, house ownership, house age and number of bedrooms, Invercargill
Average heating cost per month (winter)
House ownership
Age of dwelling
Number of bedrooms
Text description of figure
There are four bar graphs. The first graph sets out the average heating cost per month in winter. Cost per month by heating methods are: electric $119, gas $115, open fire $55, wood burner $60, pellet burner $76, Multi-fuel $155 and oil $123.
The second graph sets out heating methods divided by home tenure. For households living in rentals 2601 use electric, 1248 use gas, 312 use open fire, 312 use wood burners, 0 use pellet burners, 832 use multi-fuel and 104 use oil. For households living in their on house 7699 use electricity, 1665 use gas, 936 use open fires, 2497 use wood burners, 312 use pellet burners, 4,682 use multi-fuel and 312 use oil.
The third graph sets out the age of a dwelling using a particular method of heating.
- Heating methods for houses under 10 years old are 8% electric, 4% gas, 4% wood burners, 2% multi fuel and 0% open fires.
- Heating methods for houses between 11 and 20 years old are 7% electric, 11 gas, 4% wood burners, 9% multi fuel and 0% open fires.
- Heating methods for houses between 21 and 40 years old are 38% electric, 21% gas, 33% wood burners, 34% multi fuel and 50% open fires.
- Heating methods for houses over 41years old are 34% electric, 39% gas, 56% wood burners, 43% multi fuel and 42% open fires.
The fourth graph sets out particular heating methods by the number of bedrooms.
- Heating methods for houses with one bedroom are 2% electricity, 0% gas, 0% wood burner, 0% multi fuel and 0% open fire.
- Heating methods for houses with two bedrooms are 28% electricity, 18% gas, 11% wood burner, 6% multi fuel and 0% open fire.
- Heating methods for houses with three bedrooms are 56% electricity, 61% gas, 74% wood burner, 74% multi fuel and 75% open fire.
- Heating methods for houses with four bedrooms are 9% electricity, 14% gas, 11% wood burner, 17% multi fuel and 17% open fire.
- Heating methods for houses with five bedrooms are 2% electricity, 4% gas, 4% wood burner, 2% multi fuel and 8% open fire.
- Heating methods for houses with six bedrooms are 0% electricity, 0% gas, 0% wood burner, 0% multi fuel and 0% open fire.
Table 5.6: Type of electric heating, Invercargill
The main difference in the types of electric heaters used in Invercargill was the prevalence of heat pumps, which were used by 30% of households compared to a national average of 13% (Table 5.6). Night store heaters were also more common, with 21% of households using electricity having this form of heater.
Table 5.7: Home heating method, by house ownership, Invercargill
Around 23% of respondents in Invercargill were living in rented accommodation (Table 5.7).
Household insulation types and heating methods are shown in Tables 5.8 and 5.9. Table 5.10 shows home heating method by household income. The overall non-response rate was around 26%. This limits the use of these data, because there may be an income bias in the non-respondents.
Table 5.8: House insulation summary statistics, Invercargill
Table 5.9: Degree of house insulation, by heating method, Invercargill
Table 5.10: Home heating method, by household income, Invercargill
Tables 5.11 and 5.12 show the relationship between heating methods and the age of the dwelling and number of bedrooms, respectively.
