The experts agree that batteries make economic sense for households with higher-than-average energy usage and where the house is unoccupied for much of the day where, without a battery, solar power generated during the day is mostly wasted. And, of course, some people are also going solar for environmental reasons and want to be as close to "off grid" as possible, so will add a battery. Loading Replay Replay video Play video Play video No greenie fad Emlyn Keane, the co-founder of Evergen, which makes CSIRO-developed smart technology that drives efficiencies in solar plus battery systems, says renewable energy is not a greenie fad.

"It’s appealing to ordinary Australians who want to take control of their spending and are conscious of the impact they are making on the environment," he says. "They want a better and more sustainable future for themselves and their families – and this includes the cost benefits on offer." Mark and Julie Donovan, who have two children, Keira, 9, and Bailey, 7, paid just over $20,000 six months ago to install solar panels, a battery and smart software. They bought their four-bedroom house, which has a swimming pool, in Grays Point in Sydney's Sutherland Shire 18 months ago. Mark and Julie Donovan, with their children Keira and Bailey at their solar-powered home in Grays Point. Credit:Christopher Pearce

They installed 6kW of solar panels and a 10kWh battery, which are typical sizes for houses in Sydney and Melbourne, as well as software that maximises efficiencies. The Reposit Power software decides when to use grid power, when to use power from the battery and when to sell excess power back to the grid to maximise the savings on the family's electricity bill. "I'm concerned about climate change and it's something that financially makes sense, but there's a feel-good [factor] around it and it's good for the environment," says Mark, a 40-year-old sales manager. The pre-solar quarterly electricity bill of between $1000 and $1200 is down to about $400. With set-up costs of just over $20,000, the savings on the electricity bill makes the "payback" period likely to be six or seven years. The Donovans intend to be in the house much longer than that.

They borrowed the money to pay for the start-up costs, and the debt was added to their mortgage at a relatively low interest rate. Solar panels first Damien Moyse, policy and research manager at Renew, a not-for-profit energy advisory service, says a solar system lowers the annual bill for the typical family by $800, $900 or $1000. When you add a battery, that gives you another $200 to $300-a-year off, or maybe even $400 a year or more if you have a "big load profile, you use a lot of energy in the evenings and you pay high tariffs," Moyse says. Compared to a couple of years ago there are more situations now where you can just squeeze in a 10-year payback with a battery, Moyse says.

But there are still a lot of cases where it is a 15 years or more payback period with batteries, he says. Loading "It depends on the tariffs and the consumption profile and so on," he says. And we don't know how much power prices are going to rise in the future, he says. While about one-in-five houses have solar panels, the number with batteries is a fraction of that. That is likely to change as battery technology improves and prices fall, Moyse says.

Carolyn Lee, the founder of The Energy Experts, a solar energy broker, says a mid-range solar system of 5kW would cost, all up, including the inverter (that converts DC electricity to AC) and installation, about $6500 and more like $7500 to $8000 for a "premium" solar set-up. Jake Elliott, installer network manager at solar broker and comparison site, Solar Choice, says with battery prices falling, those installing solar panels should ensure their inverters are battery ready so that a battery can be easily added later. Reduce consumption It is important not to forget that big savings on the power bill can be made just by following a few simple tips to reduce power consumption. Moyse says putting some batteries in the roof can help, as well as buying energy-efficient electrical and white goods when they are replaced.

Carolyn Lee recommends choosing energy-efficient LEDs. "They last 10 times longer and use 90 per cent less energy than standard globes and halogen downlights," she says. She says ceiling fans are the most energy-efficient form of cooling. "Airconditioning is the mother of all domestic greenhouse pollution," Lee says. For those who don't have the cash to install solar, there are "green loans" from lenders like the Community First Credit Union, where interest rates are as low as 6 per cent. Energy retailers have interest-free loans, usually where the loan is paid back over a fixed term. There may be an annual fee and, if the loan in not repaid with the term, high interest rates usually apply.

There is also Brighte, which is a kind of "buy now, pay later" app like AfterPay, except it connects solar installers with households wanting to upgrade their homes. With additional reporting by Cole Latimer.