Understanding how to use a solar system to charge your EV doesn’t need to be complicated. Here’s how to maximise energy efficiency when charging your EV.
Sustainability
How to store solar energy for night use and what capacity is needed
The key to saving money with solar is to use free energy generated by your rooftop panels to power your home, which negates the need to buy electricity from the grid. Here's how to use your solar energy at night.
Saving money with solar power at night can be tricky because your solar panels are not generating electricity after the sun sets. One way you can make the most of your solar investment and reduce energy costs during the evening and overnight is to install a solar battery system.
With a battery, you can store excess solar power during the day to use when your panels aren’t generating energy, for example during the evening peak. This means you can reduce the amount of electricity you’re buying day and night, leading to greater savings on your energy bills.
In this article
How to store solar energy to use at night
How do solar batteries work?
With solar panels and a battery, any excess solar you’re not using when your panels are generating electricity will be stored in the battery. When the sun goes down, and your panels stop generating electricity, your home will start using power from your battery rather than from the energy grid, which you pay for via your energy provider.
Batteries can also be charged with electricity from the grid during off-peak times, for example overnight, to use during peak times when electricity is more expensive. It is, however, important to take care and avoid charging and discharging your battery too often because this can shorten its lifespan.
Why get a solar battery?
According to Solar Victoria, most households with only solar panels use around 25 per cent of the energy they generate, while households with panels and a battery use around 50 to 60 per cent.
Financially, maximising the amount of solar power you use in your home makes more sense than using less and exporting the excess. This is because solar feed-in tariffs (the rates paid to customers who put electricity back into the grid) are significantly lower than usage rates (the amount you pay to use energy from the grid). So you stand to save more from not buying energy than you do from being paid for exporting it to the grid.
But batteries have other benefits too, including blackout protection and reducing strain on the electricity grid. A battery with blackout protection, for example, will keep some or all your power on during a power outage. For households in areas that experience blackouts, this can be invaluable.
Will feed-in tariffs be reduced?
State governments review feed-in tariffs each year and set a minimum feed-in tariff retailers must pay their customers.
Due to decreasing daytime wholesale electricity prices, feed-in tariffs have been declining for years, and will continue to do so. For example, from July 2024, the flat minimum feed-in tariff was 3.3 cents per kilowatt hour. From July 2025, it is proposed to be 0.04 cents per kilowatt hour.
Therefore, solar households need to start focusing on using and storing their solar power – that means using appliances during the day or storing solar power in a battery to use later on.
Solar batteries may offer blackout protection.
Are solar batteries financially worth it?
While the savings from adding a battery are clear, batteries are still relatively expensive. There are interest-free loans available to assist with the upfront cost; however, if your motivations for getting one are purely financial, households must weigh up the cost of the battery with the potential savings it might deliver.
Consider:
- How do you use energy?
- What size battery would you need?
- The cost vs savings
How does your household use energy?
Do you use energy during the day or does most of your usage happen in the evening?
Many appliances, such as dishwashers, washing machines and dryers, have built-in timers to run in the middle of the day, even if you’re out. Similarly, many heaters and air conditioners can be set to heat or cool the house when the sun is shining, so it’s comfortable when you come home after work. Or, if you have an electric vehicle that’s parked at home during the day, it can be charged using solar power to drastically reduce your car running costs too.
These days there are even smart appliances and monitoring systems you can use to control your appliances remotely. So you can turn your appliances on and off from anywhere and sync them up with your solar generation.
If you can use solar energy during the day, you might be able to maximise your solar investment without a battery. But this isn’t possible for everyone, so if you need to use lots of energy when your panels aren’t generating electricity, a battery might make sense for you.
More: What is Vehicle to Load (V2L) for electric vehicles?
What size solar battery do you need?
Work with your installer to get the right size battery for you. Too big and you’ll be paying for capacity that you’re not using; too small and it won’t be big enough to meet your needs.
The right size battery will be determined by:
- The size of your solar panel system
- How much electricity you use overnight
- Whether you want blackout protection or not.
Also consider any plans for the future – are you likely to be using more electricity? Perhaps you have a growing family or are thinking about replacing gas appliances, such as a hot water system, heater or cooktop, with electric ones down the track?
Generally, you should aim to get a battery you can regularly charge and discharge to the recommended level – one you can fill with solar power each day and then use up later on. If you want blackout protection, you might need extra capacity to ensure you have electricity stored in case of an outage.
Work with your solar installer to find the right size battery for you. Image: Matt Harvey
How much does a solar battery cost? How much could you save?
Depending on the size and quality of your battery, you can expect to pay around $1,000 - $1,200 per kWh of storage. So, for example, a 6kWh battery might cost around $7,200 ($1,200 x 6 = $7,200).
There aren’t any rebates available for batteries, but Solar Victoria offers eligible households an interest-free loan of up to $8,800 for the installation of a solar battery system. This reduces the upfront cost and is repaid in monthly instalments of up to $183.34 over 4 years.
This can be a good benchmark by which to measure whether the savings from a battery would stack up for you financially. What proportion of the monthly repayments could be offset by the savings?
Does solar work on cloudy days?
Solar panels will still generate electricity on cloudy days, they’re less efficient, which means their energy output will be reduced.
Depending on the size of your solar system and how many appliances you’re running, on cloudy days your home might need to draw on energy from the grid to supplement your solar generation. However, if you have a battery, you’ll be able to use the solar power stored in that instead.
