About the calculator

This is beta software, and is subject to change at any time.

This tool is designed to provide a rapid initial assessment of the likely suitability of a various low grid electricity consumption heating and cooling product types. Typically these products may not provide guaranteed comfort in the building for certain combinations of conditions, either because they use solar energy which is intermittent, or because of the way they operate. However, often they will still provide a useful improvement in comfort, and typically the cost of running these devices is much less than the cost of running a conventional grid connected air-conditioner.

This tool allows users who may not be familiar with these products to make their own assessment of whether different product types are likely to meet their expectations of comfort for their particular location and usage pattern. This tool is not a substitute for a detailed selection and sizing process, and should not be relied upon to make the final product selection.

This tool calculates the sub-hourly operation of an average performing version of the air-cooling or heating product over a year in a representative building and using local climate data for the specified location. Since the details of the actual building or room to be air-conditioned and the actual air-conditioning product will have a substantial influence on performance, the results should be used as a guide only. For example, it may be instructive to explore how the performance of the chosen product changes with location or with different assumed usage patterns.

Building Types

Residential (detached)
This building is designed to replicate a typical brick veneer house on a concrete slab with ceiling insulation and a pitched tiled roof but no wall insulation. Unshaded double glazed windows are oriented uniformly in all directions, and the building is not well sealed. Typical heat loads from appliances, lighting and occupants are assumed.

Residential (apartment)
This building is designed to replicate an apartment located within a typical low-rise building with concrete block construction. The building is better sealed than the detached residential building. Heat loads from appliances, lighting and occupants are designed to reflect typical values for apartment buildings.

Commercial office
This building has the same base construction as the residential apartment building but with heat loads designed to match a typical office configuration and occupancy pattern.


Indirect Evaporative Cooler
This product models a dew-point indirect evaporative cooler using a mixture of fresh air and return air to cool the space. Indirect evaporative coolers cool a primary air-stream without adding moisture by transferring heat to a second airstream that is evaporatively cooled. The primary airstream enters the indoor space while the wet secondary airstream exhausts to outside. This allows indirect evaporative coolers to work in locations or at times when the humidity is too high for conventional direct evaporative coolers. However, they are typically not effective in tropical climates. Indirect coolers use a small amount of power to drive fans and pumps. This device is controlled to provide cooling only.

Solar Air Heater
This product models an unglazed, roof mounted, open loop solar air heating collector facing north with a slope equal to 22.5°. Open loop collectors heat 100% outside (i.e. fresh) air. These devices do not store heat, hence they only provide heating when it’s sunny. However, heating supplied to the space during the day may carry over into the evening. Solar air heaters use a small amount of power to drive fans, though sometimes they can also be powered by a photovoltaic panel. This device is controlled to provide heating only.

Photovoltaic Air-conditioner
This product models a high efficiency reverse-cycle vapour-compression air-conditioner connected to dedicated solar-photovoltaic panels facing north at a slope equal to 22.5°. A battery storage system sized to allow 20 minutes of operation is assumed to ensure stable operation. The size of the photovoltaic array is scaled with the size of the air-conditioner and is such that the PV output at the nominal rated condition is at least 50% higher than the air-conditioner nominal rated electrical power consumption. Operation with grid electricity is not allowed, and there is no export of excess generated electricity. Air-conditioners use power to drive the compressor and air-supply fans. This device operates with 100% recirculation of building air and can provide cooling or heating.