Sorry, meter box full
The future is electric, and the sooner you stop burning fossil fuels the better… for your pocket and your planet.
After installing photovoltaic panels early in 2020 we have been working hard to make our home and lifestyle more efficient and to expand and optimise the various ways we use electricity.
Renewable energy and electricity
Renewable energy sources such as sun, wind and hydro produce electricity with very low greenhouse gas emissions, but the sun does not always shine nor the wind always blow. Unlike coal, gas or nuclear energy, renewable energy is not available continuously, so storage, or the ‘banking’ of energy is required, to ride out those dark and windless times.
To play our part in ushering in a fully renewable energy economy, we have completely done away with the gas service on our property. When our LPG BBQ dies we will also find an electric replacement. Doing away with the occasional wood fire pit will be much harder… though David Holmgren argues in support of wood. He notes that ‘even poorly managed woodlands supplying wood heaters up to 400km away, have a net greenhouse gas production of one third that of natural gas and one tenth that of coal-fired electricity.’
Our electricity subscription is with Powershop, mainly because they offset all carbon associated with their customers’ energy usage, and have done since 2015. Even though our recently installed 4.9 kw photovoltaic (PV) system averages 120% of our daily power needs at present (November 2020), we will depend on the grid for cloudy days, shorter days and breakdowns. For us, subscribing to a collectively useful electricity grid also represents a more democratic option than going autonomous or completely off-the-grid.
The rise in home PV’s
The number of residential photovoltaic installations in Australia continues to grow. We reinforced this trend in February 2020 when we installed a 4.9 kw system at our house and joined the massive 1 in 5 Australian households with their own PV systems.
On average, Australians currently have the biggest uptake of home PV systems of any nation. This accolade makes sense on a number of fronts. Firstly, Australia benefits from particularly high insolation due to a combination of latitudinal location and a dry climate. PV’s will produce greater outputs when they receive more sunshine.
Secondly, we are a suburban nation characterised by lower density urban environments. Our ratio of torrens-titled roof area, to energy loads, is high. This means that householders have complete control over their privately owned roof area, and with PV installations they can individually capitalise on it.
Thirdly, and perhaps most significantly, are the generous Australian government incentives for PV’s that commenced more than two decades ago. These incentives began with the 1999 Liberal-National Coalition Government launching the Photovoltaic Rebate Program, a rebate plan designed to offset negative impacts of the newly introduced GST. A maximum of $8,250 matching grant per household was initially available under this scheme, reduced to $4,000 in 2005.
In the pre-election budget of May 2007, the government announced an extension of the program and a doubling of the rebate up to a maximum of $8,000 per household. The November 2007 elected Labor Government maintained the scheme but renamed it the Solar Homes and Communities Program (SHCP) whilst limiting eligibility to grid-connected PV systems.
Popularity of the scheme, triggered by the higher rebate and rising public interest in climate change, saw enormous growth (as described in the graph below) that led to significant oversubscription. A new means test limited payments to households with an annual income below $100k but did little to slow interest and substantial overrun costs led the government to close the SHCP in June 2009.
The Australian Government now uses Small- Scale Technology Certificates (STC's) as a financial incentive for installing PV systems. Depending on which zone a system is installed in an applicant will benefit from a saving of about 25 – 30% on the supply and install cost. The STC incentive on PV’s is set to be slowly phase out, completing in late 2030.
Successful residential applicants (by year of application) and total installed watts (MW)* under the PVRP-SHCP, 2000 to 2010
(Source: Macintosh, A & Wilkinson, D 2010, The Australian Government’s solar PV rebate program An evaluation of its cost-effectiveness and fairness, ANU Centre for Climate Law and Policy)
Electricity cost/price extrapolations
Energy flows into and out of our property fluctuate depending on the weather, the time of day, who is home and what their habits are.
Household electricity costs in NSW have increased by a whopping 100.9% over the last ten years (to 2019). As of November 2020 we pay a daily fee of 101.05 c for the privilege of being connected to the grid. On top of this we pay usage fees with a peak metered rate of 21.84 c/kwh and an off-peak metered rate of 11.88 c/kwh.
“Selling power back to the grid will be even less attractive a prospect, moving into the future.”
Solar feed-in tariffs for NSW have dropped from a once generous rate of 20.00 c/kwh in 2010. Currently, when our PV’s generate power that we can’t immediately use or store on site, we sell that power back to the grid at the solar feed-in tariff rate of just 7.00 c/kwh - a value disparity of one-third when compared to inbound energy in the same time period.
If respective rates of growth and decline trend at only half that amount over the ten years ahead, the value disparity will be closer to a dismal one-tenth. The simple take-home message when extrapolating these trends, is that selling power back to the grid will be even less attractive a prospect, moving into the future.
Banking energy at home
Renewable energy providers can bank energy for later using ‘pumped hydro energy storage’ (97% market share) or to a lesser but growing extent, large-scaled battery installations. Energy distributors are exploring community batteries that they own and maintain, and charge solar customers a storage fee for use. But to minimise exposure to the growing value disparity with solar feed-in tariffs, how can we keep our energy at home?
Firstly, simply using electricity when the sun is shining (on your PV’s) makes excellent sense. With some considered management and organisation, air conditioners, heaters, dryers, washing machines, dishwashers and slow cookers can all be timed to run during the sunniest hours of the day.
Hot water systems make up a quarter of average household energy usage and are an excellent place to direct energy to before sending it back to the grid. After much research and calculation, we have retained our very old resistance element hot water system (hate landfilling anything that works) but installed a very clever solar hot water diverter called the Catch Power Green II.
The diverter lives in the meter box and sends any surplus electricity from PV’s directly to our hot water system. The solar hot water diverter allows us to store energy at a cost significantly lower than batteries would. If there is an overcast day where insufficient PV electricity is diverted to the hot water system, then the diverter waits till the cheaper off-peak rates before heating till the internal thermostat cut-off is met.
We considered a heat pump hot water system but heat pump electronics are not well suited to the fluctuations in excess PV diversion. Whilst they are significantly more efficient (using around 75% less electricity), they are also a more complex solution than a resistance element system, with many moving parts. Only the Sanden Eco met both our acoustic and environmental criteria, but at around five times the cost of the hot water diverter, we thought the money might be better spent adding another 3kw of PV’s to the roof some day. And the pay-back period seemed to be around 14 years.
Another great keep-your-energy-at-home product from Catch is their Solar Relay - a multifunction timer for electrical loads that need to be controlled based on time, or how much energy your solar system is producing, or a combination of both. We will consider this device if we ever install a reverse cycle air conditioner or underfloor heating.
With the addition of the Catch Power Green II (top LHS) our meter box is pretty much full.
PV charged electric vehicles?!?!
There’s another first-of-it’s-kind device that might end up in our very cramped meter box one day. It’s a Zappi smart EV charger. As well as operating in standard EV charger mode the Zappi has a green mode that only uses energy generated on site from PV or wind. In this mode, the Zappi effectively allows you to ‘bank’ solar power into your EV’s battery.
Let’s take a quick comparative look at the energy consumption and costs of EV’s then speculate on how that might impact your PV and broader household energy systems...
The Tesla standard model T3 has a battery capacity of 50 kWh with a range of 354 km. That equates to 141.2 Wh per km or 14.1 kWh per 100 km. If we are charging at home on our peak metered rate of 21.84 c/kwh the energy for a 100 km drive in a T3 would cost us $3.07.
A petrol powered Honda Civic consumes 6.4 litres of petrol per 100 km. ULP 91 costs $1.27 per litre today meaning the 100 km in the Civic would cost you $8.13. On that basis the T3 is 62% cheaper to run.
The average battery size in an electric vehicle is around five times the size of a typical home battery. Electric vehicle batteries could be an interesting alternative household energy source to a home battery in the future, but we are not quite there yet. The technology, when it arrives, is called V2H or vehicle-to-home.
Some speculation on this possibility in the context of PV energy autonomy is interesting. The average passenger vehicle in Australia travels 34.5km per day. For a T3 the daily top-up charge to meet this demand would be approximately 4.9 kWh. The T3 top-up charge is a 27% increase on the current average daily household electricity consumption (which is 18.2 kWh for 2516 postcode).
Fun fact: A 100 km drive in the T3 uses 14.1 kWh of electricity. This is pretty much equivalent to fully heating a 400 litre hot water system from dead cold at 15 kWh.
Of course charging a decent cargo eBike or two is a simpler business altogether. Batteries are 100 times smaller than the T3’s at around 500 Wh whilst still providing a range of up to 135km!
