How a Tesla Powerwall installation in Gisborne reduced costs and gave grid independence. Andrew purchased a house in Gisborne and realised that his heating and was too reliant on the grid.

The issue:

• Country location – Gisborne
• Electricity charges $150 per month
•  LPG charges $180 per month

 

The Solution:

• 7.5 kW Solar coupled with a Tesla Powerwall2 and Powerdiverter

 

The result:

• House 85% self-powered for the year
• Total energy bill for 2018 was $464 ($38 average per month)

 

Let’s hear it in Andrew’s own words.

Around two years ago we moved to a new home approx. 50km from Melbourne in a town called Gisborne. The house has 4 bedrooms, large living space and was built in the early 1980s. It’s approx. 2kms out of town on 1.5 acres and is not connected to the town gas supply. The existing hot water is electric, heating was bottled LPG and cooling was an old ducted refrigerated AC. As it stood, the house was expensive to run and had a massive reliance on fossil fuels.

Having installed a small solar system on our previous house, I quickly planned to install solar on the new home and move to be as self-sufficient as possible.

 

Solar System Installed

Within a couple of months of moving in, a 7.5kw solar system was installed. We also installed a Powerdiverter unit to divert excess solar production to the electric hot water service. A split system AC was installed in the living space and we stopped using the existing LPG heater. Soon after, an order for a Tesla Powerwall2 was placed.

After a 3 month wait, the Powerwall2 arrived in early November 2017. This has enabled our house to be >99% self-powered from early September to mid May and 85% self-powered for the year.

In May 2018, the old ducted gas/refrigerated AC was replaced with a 14kw Fujitsu ducted unit. This enabled the whole house to be heated/cooled.

Gisborne is located at an elevation of approx. 430m and has temperatures from a low -4°C in Winter to >40°C in Summer. The average overall temperature for June-August is 8°C.

Hot water costs

Hot water is approx. 30-40% of our total energy usage with heating/cooling and pool pumps the other major consumers. The only non-electric appliance is our gas cook top. This runs of bottled LPG with a 45kg bottle lasting approx. 2 years.

It costs approx. $1.10 to be connected to the grid each day. Currently we receive $0.099 per kwh feed-in and during the summer months this is enough to offset the grid connection charges. Our total energy bill for 2018 was $464 (grid connection and usage charges). As a comparison, before the solar Powerwall reverse cycle was installed, our electricity charges were $150 per month plus $180 per month in LPG to heat the living space during the colder months.

Screenshots of stats from the Tesla app.

A good friend of mine who’s pretty handy knocked up a script to pull data from the Powerwall API and push this up to PV Output. This has the advantage of tracking state of charge over time. In the future I would like to use the API data to automate the running of pool pumps and other appliances.

Here’s a basic overview of how everything is connected.