With positive hype surrounding home battery systems, it’s easy to get caught up in the momentum without considering all the facts.
Tesla’s Powerwall is a wall mounted home battery system designed to store electricity generated from rooftop solar panels during the day, so that the electricity can be used when energy prices are significantly higher or at night.
Alternatively, Sun Plan Solar PV from Sumo Power is an energy package intended to top up the energy of solar powered homes by offering bonus power to consumers that can be used when solar power just isn’t enough (like at night).
Is the Tesla Powerwall or Sun Plan Solar PV Package the better option?
Tesla’s Powerwall has a 7kWh energy storage capacity, which is sufficient to power most homes during the evening. The battery can be charged with electricity generated by solar panels throughout the day or with electricity from the grid in off peak periods when grid power is cheaper. Multiple batteries may be installed together for homes with greater energy needs and, on a sunny day, full charge can be achieved by 11am.
The Powerwall also runs on a daily cycle, meaning that any electricity that is stored throughout the day and not used in the evening will be fed back into the grid.
By comparison, Sun Plan gives customers the first 8kWh of grid-powered electricity at no extra charge, every day for 12 months, which can be used to top-up your daytime solar power. There is no need to buy an expensive battery.
Are they financially viable?
For most people, the appeal of battery storage is the prospect of supplying your own electricity and gaining independence from energy providers by going off-grid. But is this a financially viable option?
The Tesla Powerwall comes with a 10-year warranty and will continue to work after this period, but at a reduced capacity. According to Choice, the payback time will vary from household to household depending on individual energy use, but calculations indicate they may well exceed the warranty period for most households.
Additionally, if all the charge is used from the battery or there is not enough solar energy due to a cloudy day, the house will still draw electricity from the grid as needed, incurring extra costs.
All energy providers offer feed-in tariffs for excess energy fed back into the grid (feed-in tariffs are also available with Sun Plan), however these financial returns are unlikely to make a large impact on the payback period.
On the other hand, the Sun Plan Solar PV Package is designed to bring costs down. Invest in solar panels and for the first 12 months, consumers will receive $0 supply charge, $0 for the first 8kWh grid-supplied electricity usage each day, and if they exceed the 8kWh on average over a month, the cost is only 20 cents per kWh for the excess power.
Is cost the main factor?
For some people, battery systems mean more than saving money. One Consumer Pulse survey completed by Choice found that two thirds of Australians want to sever ties with energy providers and become self-sufficient in meeting their energy requirements. But with battery storage systems still relying on the energy grid to top up consumer’s needs, this independence will be some time away.
What is the most worthwhile option?
Individual household requirements need to be assessed to determine the most viable option. As technology continues to advance at rapid speed and new options hit the market, consumers will need to weigh up the spend versus payback along with their motivation behind the purchase.
About the author
Domenic Capomolla is the founder and CEO of Sumo Power. Having worked in the energy industry for close to 20 years, Domenic is an expert on deregulated and contestable power and gas markets.