Net Carbon Negative Home

By John

We’re a retired couple, and bought a 1960s brick veneer in suburban Wangaratta in November 2020. We expect this will be our last home.

We have just finished adding a solar system and a small home battery, and are continuing to improve insulation and draft proofing.

We bought the house for its style, and it had the space we wanted, a roof for solar, a place for a battery and its location close enough to shopping and town to reduce car use. It came with electric everything except an old gas heater ready for replacement with a reverse cycle air conditioner.

The changes we’re making are guided by enthusiasm for and lots of reading about renewable energy. Information comes from the Renew Economy and The Driven newsletters, attending energy conferences and webinars, and learning from a long interest in efficient housing.

Our goal, and plans to achieve it

Our goal was to make the house net carbon negative, all electric.

The plan called for:

  • solar panels
  • a home battery
  • reverse cycle air conditioner heating
  • rescheduling water heating to the afternoon

We’d need grid electricity at times, especially for the air conditioners during winter, and to reduce the carbon impact we’d buy fully carbon offset power.

Being carbon negative, we’re comfortable to run our older but functional fridge, washing machine dishwasher and electric hot water through their effective lives. We’ve also stayed with a ceramic cooktop rather than changing to a more efficient induction model.

Boxes ticked

We now have a 7.5kW solar system, half facing NNE, half facing WNW and a 5.1 kWh battery, which can have up to three 2.6kWh modules added.

Reverse cycle air conditioner for heating and cooling are in the living area and each bedroom.

The house has good cross ventilation for summer cooling, and an old but effective evaporative a/c ,which came with the house, for additional cooling.

Gap filling and topping up old ceiling insulation, with a layer of R5.0 EarthWool batts have started. We’ve made a big jump towards sustainability. We’ll continue the small steps in the future.

The Spend

The solar system and battery have cost around $14,000, with the Victorian government contributing another $4,174 to the battery.

Air Conditioners to replace gas and electric heaters have cost another $10,000.

The Payback

Our solar is making much more power than we use most days and the battery, which has just been installed, is powering the house well into the night. We expect it will take us right through the night as the weather warms.

The air conditioners are using half the power of our old heaters.

Our house now emits no CO2. Any electricity generation emissions are both offset and made up for by our generation at other times.

We buy very little electricity, and expect the feed in tariff will pay most of our daily connection fee. There is no gas bill.

We’re happy with what we’ve achieved, and count ourselves as fortunate to be able to afford to do it all.

We’re confident the solar will pay for itself. The battery may not do the same, but it is saving money as it powers the house through every evening, and we enjoy the large degree of self sufficiency it provides.

In the future

Water heating will be rescheduled very soon. We will replace the old hot water system with a more efficient heat pump, and we’ll do something to reduce winter heat loss through our windows. Underfloor insulation is planned for this summer.

We expect to get an electric car in a few years, and to fuel it mainly from our solar. We expect the car will be able to power the house as well as our driving.


In the future an electric car which can store more of our solar electricity, will sit in the garage ready to power the house when it’s not out decarbonising our transport.

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