ABC News Online interviewed Gary about our Tesla Powerwall and the NSW Government solar feed-in tariff scheme that was terminated at the end of December 2016.
The online story can be found here on the ABC News Online website.
The Powerwall has been successfully and actively contributing to our household power management.
But we’ve made some changes to the home setup.
The day after it was announced that Tesla’s Powerwall would become available, I had Natural Solar on site working out what our system would look like, and how many panels we could fit on our remaining roof space.
Remaining roof space? Yes – we installed a seven-panel Sharp system in 2010 – with seven 220W panels and inverter.
So, then we had two separate solar panel arrays, one connected directly to the grid; the other connected to our Tesla Powerwall.
The original Sharp solar array ran through a “gross feed-in tariff” meter; the new system ran through a “nett feed-in tariff” meter so we use all available power in the house and only export any excess power that we cannot consume or store.
Coupled with online real-time monitoring from our friends at Solar Analytics, we are able to see exactly what our power generation and power consumption is, with second-by-second vision of selected power circuits in the house.
And our SolarEdge inverter is logging data to their SolarEdge servers.
Monitoring also allows us to assess the performance over time of our solar arrays, ensuring that they remain delivering at peak operational performance.
Above all, with so-called “smart metering” becoming the default method of charging for electricity, we are able to decide when to run high-demand appliances such as the dishwasher, washing machine and air conditioner.
Scheduling appliances to run when electricity is cheapest (between 10 pm and 7 am) along the lines of the older “off peak” systems, allows us to minimise our power costs.
All this positioned us for the end of the solar bonus scheme when we lost the rebate for the energy we put into the grid from our original Sharp solar array.
In early 2017 these panels were disconnected from the “gross feed-in tariff” metering system and redirected to supply power directly to the household circuits, converting us to a “nett feed-in tariff”.
Since our nett feed-in meter has been installed, we’ve sent less than three kilowatt-hours to the grid from the new array and Powerwall, proving that what we’re generating from our new panels is serving us, and not the energy distributors. At current nett feed-in rebates, these three kilowatt-hours are worth a total of about eighteen cents!!
To us, kilowatt-hours are worth up to 46 cents each.
Winter – and the system works well, even without the benefit of energy from the original solar array.
Summer – look out!!!
Gary was interviewed as part of an extended ABC News Online piece being prepared by Amy Bainbridge in regards to bill shock as the solar rebate scheme in various states was withdrawn. The first part of the article is found with the title “Bill shock looms as lucrative solar tariffs roll back, advocates warn“. The second part of the article can be found with the title “Batteries, meters, cutting back: How Australians plan to beat solar tariff bill shock“.
But wait – there’s more.
Here come the steak knives!!!
Having two separate arrays and inverters seemed the wrong way to go, so I began discussions with Australia Wide Solar about changing our configuration and adding Reposit.
As a result the seven Sharp 220W panels were replaced with nine 360W Sunpower panels with Maximum Power Point Trackers, or DC Optimisers, and these were added into the SolarEdge inverter for a total of twenty panels.
Reposit is a clever little unit indeed.
It “anticipates” the conditions under which the solar panels and battery will be operating.
I used to have the SolarEdge inverter programmed (manually) so that from 0500 to 0700 each weekday morning the Powerwall battery was charged from the grid, leaving a good capacity in the battery at 0700 – when the electricity tariff changes from “Off Peak” to “Shoulder”.
That allowed the house to run on stored energy from 0700 – effectively taking us off grid – until sunlight is strong enough to not only power all household load, but recharge the Powerwall.
Now, the Reposit unit makes those changes dynamically – in anticipation of what it knows the household load to be, and of the weather forecast for the day ahead.
Of course, now that everything is tied together through just one inverter (to SolarEdge Inverter, and no longer the older Sharp Inverter) it is much easier to know exactly where the electricity is flowing through the system: how much solar energy is generated; how much is being used by the household; how much is being stored for later use; how much is being exported to the grid.
A major event I expect to occur this summer will be “grid events” – times during which the wholesale price of energy is high enough for it to be worthwhile dumping our stored energy back in to the grid for a return of up to $1.00 per kWh.
That sounds great, but since we’re still buying power – presumably, due to high grid demand, at the peak tariff of up to $0.50 per kWh – the saving is good, but not earth-shattering.
That’s not the point, however. If our only driving force was to calculate the pay-back period for our investment, that’s not going to work.
There are too many variables: future costs per kWh and inflation; changes to the daily grid access / network charge; our household load; the number and extent of sunny days.
All we can do is assume that the costs of electricity will continue to rise. If we can run routine functions such as washing clothes and dishes during the day when sunlight is free, other household functions will take care of themselves.
We still have some tweaking and fine-tuning to do, but that’s most of the fun, isn’t it?
So, more lessons learned and opportunities for more tweaking as the sun patterns head toward summer.