All-electric home case study

It’s fair to say that 80-year-old John Heij and his wife Elizabeth are early adopters. It was 2004 when they first installed a small solar and battery system to run lights and computers in their home in the Aldinga Arts EcoVillage, on the coast south of Adelaide in South Australia. Then, in 2013, they designed and built a new house (in the same village), and as part of that, installed a larger hybrid (grid-connected) system to run their entire all-electric home and electric vehicle (EV). In addition, they’re effectively off-grid for water, with two 22.5 kilolitre in-ground rainwater storage tanks that have supplied all their water needs for the last three years. Their power system comprises 9.6 kilowatts of Canadian Solar panels, two 5 kilowatt Kaco/ Selectronic inverters, a Selectronic SP-Pro inverter-charger and 32 kilowatt-hours of Sonnenschein sealed lead-acid gel batteries, configured in an AC coupled system. The size of the system means they import “less than half a kilowatt-hour per day” of electricity from the grid — a tiny proportion of the average import of 19 kWh/day in their area for two-person homes (as noted on their most recent ‘bill’—or rather, credit—from AGL). Of course, their actual energy usage is higher, with most of their 7 to 18 kWh daily usage (based on June to August 2016 usage figures, higher when charging the EV) coming from the solar panels or the batteries. The system cost between $30,000 and $35,000, but John notes that they would have done it “no matter the cost”. It’s a philosophical issue for them: “If the powers that be aren’t going to remove coal and gas, we have to do something about it ourselves,” he says.

Solar diverter

One of the interesting features of the system is the inclusion of a Sunnymate diverter (now called the SunMate) which optimally directs the solar energy. It starts by first charging the batteries, then diverts to the solar hot water system’s electric water tank element, then to the heater in the house. Elizabeth notes: “The air conditioner has to be managed manually as the Sunnymate doesn’t seem to handle motor-driven equipment. This apparently can be overcome by using relays but we haven’t gone that far yet. It handles the heater well as it is a resistive load.” Since installing the system, they’ve never had to heat water from the grid: “even on the dullest days, it always manages to heat water.” John adds that they never get a full day of rain in their area, so there’s always some generation. The Sunnymate can also control charging of their electric car. They only charge the car during the day and most of that charge is from solar. “We’re a bit different than some people as we’re retired and can organise our energy use for during the day,” notes John.

Driving range

Their car is a Nissan Leaf with a 25 kWh battery. As “homebods”, they’ve found the car’s 145 km range not a problem at all. They use it for shopping and local trips, with a recharge usually taking up to four hours at about 2.7 kWh per hour; they rarely run the car battery down below about 60% state of charge. The car’s range varies according to headwinds and hills—and the weather. “Batteries don’t like the cold, a bit like me,” says John. They have an arrangement with a friend to swap cars if they need to go on a longer trip. The system is set up to export energy to the grid, though after installing this newer system they lost their 25c/kWh feed-in tariff, and now get paid 8c/kWh, reducing again to 5.6c/kWh soon. The system prevents export from the batteries, as to date that’s been “frowned on by the network operators.”

Working the house

The house is super-insulated, with double glazing and windows oriented for winter heat gain. They have internal thermal mass in a stone wall, which absorbs the sun’s warmth during the day, along with heat from a 4 kW Derby ceramic heater, and then re-emits that heat at night. Usually the ceramic heater only runs when excess energy is diverted to it by the SunnyMate, and they find the house stays cosy overnight. In summer, they do the opposite. They cool using their ducted reverse-cycle air conditioning from 11 am to 3 pm, generally enough for the house to stay cool overnight, when combined with using fans and opening windows to access the “gully winds” from the hills or sea breezes. “To run a sustainable home you need to work the house,” says John—to open it up when needed, or shut it down, and heat/cool at the best times of the day for that. When it comes to cooking, they “hardly ever use the oven” as they find it uses too much energy. Mostly they use their microwave and induction cooktop—Elizabeth used to love cooking with gas, but now prefers induction. “It only took about five minutes to adapt,” she says, adding that it’s even quicker to respond than gas.


They do little monitoring of the system other than to check every couple of days that the batteries are charged and the inverters are on, just when “walking past them in the garage.” They have an electrician friend who does occasional more thorough checks on the system for them. They did have a fire at one stage in the DC switch: a small self-extinguishing fire, caused by a manufacturing fault. The DC switch was quickly replaced and has been taken off the market. John suggests that microinverter systems will go further to eliminate that risk. As at their last electricity ‘bill’, they’re $275 in credit—they get their credits paid to them yearly, usually in November.

Early adopter is a badge John and Elizabeth wear with pride, both to show what’s possible and to enjoy retirement without ongoing bills.

Elizabeth is a retired scientist, having worked in both agricultural plant science and sustainability across disciplines. John is a retired nurse and nurse manager. Both are now involved as volunteers in the Aldinga Arts EcoVillage in South Australia.

(Reproduced from Renew, Issue 137.)

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