Options for calculating heating capacity
Find out how to calculate the minimum heating required for your rental home’s main living area.
The Heating Assessment Tool
You can use our online heating assessment tool to calculate the minimum heating capacity required for heaters in your rental home’s main living area.
The tool asks some questions about your property. Based on your responses it will produce a report that shows the minimum heating capacity required to heat your main living room.
You can use it to check if your current heating is sufficient to meet the healthy homes heating standard, or if you need to install one or more new acceptable heaters.
The report can also help prove a rental home meets the heating requirements in the healthy homes standards.
There are 2 different formulas that can be used by the tool to calculate the heating capacity required. The tool will decide which formula to use based on the answers you provide.
Using the formula instead of the tool
If you have a complex room layout, or you’re not sure what figures to include in the Heating Assessment Tool, we recommend asking a professional for advice. They may be able to use one of the formulae in the regulations to calculate the heating capacity for you.
The formulae that industry experts can use for manual calculation can be found in schedule 2 of the Residential Tenancies (Healthy Homes Standards) Regulations 2019. The formulae are the basis for the heating assessment tool.
Healthy homes standards regulations - Schedule 2 (formula) — New Zealand Legislation(external link)
Industry professionals should note that using an alternative tool or formula cannot guarantee that the calculation will be correct under the healthy homes heating standard. A different tool may underestimate the required heating capacity or input different values, and therefore may not achieve compliance with the standard.
Heating capacity formula — New Zealand Legislation(external link)
Using manual calculations for heating capacity
If landlords choose to manually calculate heating capacity for complex layouts, there are two different heating formulas that can be used.
A new heating formula can be used by properties that are defined as a modern dwelling, home or apartment.
These include:
- Properties built to the 2008 building code.
- Relevant apartments which are a part of a residential building of at least 3 storeys and have 6 or more commercial or residential units.
- Rental properties where the insulation and glazing has been installed throughout, so that it now meets or exceeds the 2009 insulation and glazing standards.
This new heating formula will generally enable smaller heating devices to be installed to better reflect how these types of modern properties retain heat. All other types of rental properties continue to use the original formula.
If a landlord has already completed the healthy homes compliance statement with the tenancy agreement and is choosing to now use the new heating formula, they will need to provide updated information to tenants.
Using a professional to assess the required heating capacity to meet the heating standard
Landlords now have an additional pathway to comply with the heating standard. Certain qualified specialists can assess what heating capacity is acceptable for your property to meet the heating standard.
This option may be most economic for developers to use as in many cases they have already engaged a heating specialist. It could also be used by landlords who have existing qualifying heating that they believe is acceptable but doesn’t meet the capacity required by the formula or tool.
A qualified specialist is:
- a registered chartered engineer under the Chartered Professional Engineers of New Zealand Act 2002
- an International Professional Engineer (IntPE) registered with Engineering New Zealand, or
- a person that has completed a tertiary engineering, physics or building science qualification (at New Zealand Qualification Framework Level 7 or above), and has at least 5 years of experience in heating system design.
The landlord will need to keep records if this option is being used.
Records must include:
- details of the minimum required heating capacity as assessed by a qualified specialist using the criteria set out in the regulations
- a statement that the landlord is relying on this regulation (regulation 10A) and a brief description on why this regulation applies
- the name and relevant qualifications of the specialist who made the assessment
- a description of how the specialist calculated the required heating capacity
- a record of when the required heating has been installed.
Landlords will need to use this information to complete their compliance statement.
Further information
For more information or advice when installing heaters, wood burners or heat pumps, visit the following websites.
Last updated: 01 July 2025
