How does solar power work at night?

Solar panels working during the night

Do solar panels work at night?

Solar panels draw power from the sun, which is only out during the day. So technically speaking, solar panels do not work at night, because there is no sun.

Unless you are storing it, your excess (unused) solar power is being fed back into the grid. At night, your solar panels are inactive and you are using grid power to power your home.

The good news is that you can store and use your solar power at night, by installing a home solar battery.

How do home solar batteries work?

A home solar battery is a solar power storage system that can deliver power to your house. Solar batteries store the solar power sourced during the day and make it available at night.

Solar batteries give you the flexibility to use your solar power when you need to, like when there’s not enough solar power to run your house, or as backup power when the grid is down.

With the recurring outages and volatility in the grid over the past couple of years, home solar batteries are becoming increasingly popular amongst our customers.

How does solar power work at night?
Solar battery and solar inverter installation

Optimising solar power consumption

Solar batteries allow you to tailor your power usage between solar power, grid power, and backup power meaning you can optimise your solar consumption and save money.

Using PV data (the amount of solar being generated by your solar panels), your grid consumption, and your feed in (excess power being fed back into the grid) you can choose to use your stored solar power when it’s the most economical, or when grid power isn’t available.

You may choose to use grid power at off-peak times to save money on your power bills. The savings are significant.

For example, one Solstra customer who installed a home solar battery was able to, over two years, source 98% of his power from solar and only 2% from the grid. With the home solar battery, he was able to utilise more of the solar power that he generates.

Home solar battery backup power

A lot of people like to keep backup solar power in storage, to power their homes during outages. Home solar batteries have the ability to transition when there’s a requirement, fill in the gaps, and top themselves up again.

In a perfect world, when the grid goes down we can keep everything on and operate our home as usual. Unfortunately, when the power goes out and you’ve got a solar battery system, it’s a limited supply.

Therefore, there are decisions to make in terms of which powered features and home appliances are essential to you, and which ones are not (normally the fridge and the television are highlighted as important). This is a conversation we have with our customers, as this determines the way we set up your backup power and how much backup power you will have.

Residential solar battery installation Melbourne
Residential solar battery installation in Melbourne

Setting up your backup power

From a technical perspective, there are two ways we do it.

One way is a full home backup, where we cut out the biggest power-drawing appliances (like your hot water unit or ducted air conditioning). The rest of the house is fully backed up. This is a good way to do it, however, it’s best to be conservative with the power that you do use to avoid overloading the circuits (resulting in a shutdown).

The other way we do it is we backup ‘key circuits’. We might have the primary power circuit (which is either your fridge or TV) and then, for example, your lighting circuits. In some older homes, lighting circuits need to be consolidated to avoid too much load.

Transition to backup solar power

When the grid goes down, your system will facilitate the transition to backup power. The transition is completely automatic and takes milliseconds (literally!).

When the grid is connected, your solar battery is still working and delivering power to your home, as it normally would, up to its maximum capacity.

How much backup power can you get from a solar battery?

It depends on how much charge is on the battery. Typically, a battery can offer four to six hours of backup power.

If it’s during the day, some newer systems will continue to recharge via solar. So if it’s an extended, rolling blackout it’s possible to stay off-grid for quite a while.

Can I charge my EV with a solar battery?

Our customers often ask if they can charge their electric vehicle (EV) with solar power overnight, using a solar battery. The problem with EVs is that they have large batteries.

A typical home solar battery is around 10 kilowatt hours. An EV battery is around 60 to 140 kilowatt hours. To charge your EV when you get home from work, overnight, you’d need around three home solar batteries (around 30 kilowatt hours of batteries). You would need a larger solar system to do it. So it’s not really viable.

It is predicted that at some point, EV cars will actually become your home solar battery. Some EV manufacturers are already incorporating this into their designs.

Ocular 7kW EV charger installation Melbourne
Ocular 7kW EV charger installation

How much do solar batteries cost?

Here’s more good news. There are rebates and discounts available if you are looking to install a home solar battery.

Solar battery rebates

Currently, the Victorian Solar Rebate is the only rebate available for solar batteries. This is offered through the Victorian State Government. There’s no Federal rebate (at this present time). The Victorian Solar Rebate is currently $3,500 for the first 5000 rebates. Following that, the rebate decreases to $1,750.

So how much are solar batteries? 

If you’re adding a solar battery to an existing home solar system, you can expect to pay between $7,500 to $17,000, depending on the quality and size of the battery.

A typical home solar system (a 6.6 kilowatt solar system with a 10 kilowatt-hour battery) after the Victorian Solar Rebate and the Federal Government STC discount, would be around a $13,500 investment. On average, homes use around 20 to 25 kilowatt hours a day. So a system of this size would cover about 90% of your power consumption.

Are solar batteries worth it in 2022?

So the key question is… are solar batteries worthwhile? Our electricians get this question a lot too.

The return on investment for a standard solar system is around three to four years. A battery on its own (if you’ve already got solar and you install a battery), it’s about 11 years.

What is the life expectancy of a solar battery?

Battery warranties are normally around 10 years. That’s to work at, or above, 80% of its original charging capacity at the 10-year mark. So, your battery is not worthless at the end of 10 years, but it is depleted down to 80% of its original value.

Our conclusion

So to conclude, if you’re looking into solar batteries, our advice is to consider the reasons you want a solar battery installation.

If it’s to use more of your own solar power because you want to be more green and energy-efficient, that’s a great reason to install a solar battery.

If it’s just for a return on investment, depending on your circumstances and the intended use, you may be better off installing a bigger solar system.

Solstra are experts in solar, servicing homes across Melbourne and the South-Eastern suburbs. Call 0478 638 970 today to chat with one of our qualified electricians about your new or existing solar set-up and tell us what you have in mind. We’re here to help.

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