A spreadsheet model for efficient electric homes

Here’s a way of estimating the benefits of solar, energy efficiency and batteries in a home.

By Richard Keech, 2018-06-06

I was commissioned by the developers at The Cape to created a spreadsheet model to help understand the effect of different factors in an efficient electric home.  This lets you ask questions like:

  • How much money can I save by building a home to X stars?
  • Am I better off adding more solar panels or making the home more efficient?
  • What are my likely running costs if I have an X star home with Y kW of PV?
  • Is it worth putting in a battery system?
  • Is it possible to eliminate energy bills entirely


Download the spreadsheet from here: Efficient House Model.

Currently the model is setup for the climate zones of Melbourne and coastal Victoria. However I intend to extend it to include many other locales in Australia.

It includes a simple model for home energy consumption as well as including the impact of different home star ratings, and now includes the likely impact from battery systems.

The model is necessarily only an approximation and is based on lots of assumptions that may or may not make sense for you.

Zero-bill scenario

Using reasonable assumptions, the modelling shows that achieving zero energy bills is quite achievable. For example, one scenario that gives an energy bill very close to zero is shown below.

Location: Cape Paterson

Star rating: 8.0

Size of home: $134m2

Solar PV:  5.0kW

Battery: None

Occupancy:  Two people, 100%

Heating and cooling using split systems with CoP:  5.8

Daily service charge: $0.90

Energy tariff: $0.30/kWh

Feed-in tariff: $0.11/kWh







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