If you have a home battery, when you buy electricity can now be almost as important as how much electricity you use. Many electricity plans have much cheaper power during the middle of the day, and some offers include periods of free electricity.
With the right settings, your battery can charge during these cheaper periods and then supply your home later when grid electricity is more expensive. This can be particularly useful during winter, when there may not be enough solar available to fully charge your battery every day.
The best settings will depend on your electricity plan, battery and inverter size, household consumption and the capacity of your home’s electrical supply.
If you’d like some help setting this up, Clifford from Solar Wholesalers can review your system with you and help you get the important settings right.
What is grid charging and why would I charge my battery from the grid?
Grid charging is when your battery charges itself using electricity from the grid instead of from your solar panels. It can sound a little strange at first. You’ve installed solar and a battery to reduce the amount of electricity you buy from the grid — so why would you deliberately use grid power to charge it?
Because electricity prices can vary significantly depending on when you use the power. If you can charge your battery when electricity is free or inexpensive, and then use that stored energy during a more expensive period later in the day, it can significantly reduce the amount you pay for electricity.
Put simply: Charge when power is cheap. Use the battery when power is expensive.
How grid charging works with time-of-use plans
Before setting up grid charging, it’s important to understand what you’re actually paying for electricity. Time-of-use plans charge different rates at different times of day, which creates the opportunity.
The main things to look at are:
- Cheap, off-peak or free electricity periods
- Peak electricity rates and when they apply
- Your solar feed-in tariff
- The daily supply charge
For example, if your off-peak rate is 15c/kWh and your peak rate is 45c/kWh, charging 10 kWh during the cheap window saves you $3 every cycle (slightly less in practice, due to normal battery charging losses). Over a year, that adds up quickly.
Electricity retailers structure their time-of-use offers differently, so there isn’t one setting that suits every home. It’s also worth reviewing your electricity plan from time to time as the plan you had before installing a battery may not be the best plan for the way your home now uses electricity.
Why grid charging becomes essential in winter
During summer, your solar system may regularly produce enough energy to run the home and fully charge your battery. Winter is different.
There are shorter days, less solar production and often higher household electricity consumption. On a cloudy winter day, your battery might reach the evening only partly charged.
Grid charging during a cheap or free period can top it up so you have more stored energy available when electricity prices are higher.
You also don’t necessarily need the same settings all year. A grid-charging strategy that works extremely well in July may be unnecessary in January when there is plenty of solar available.
How fast should the battery charge?
This is another setting worth getting right. A larger inverter and battery may be capable of charging very quickly, but that doesn’t automatically mean it should always be set to maximum.
Your battery shares your home’s electrical supply with everything else — including air conditioning, ovens, hot water, pool equipment and EV chargers. The capacity of your electrical supply and the size of your service fuse therefore need to be considered when choosing an appropriate grid-charging rate.
The aim is to charge the battery quickly enough to take advantage of cheaper electricity, while keeping the overall electrical load sensible.
Getting the settings right
Modern battery systems give homeowners much more control than traditional solar systems did. Depending on the system, you may be able to adjust things such as:
- Grid charging times
- Charging rates
- Battery reserve levels
- Time-of-use operating modes
- When the battery charges or discharges
The best setup will vary from home to home. A household with high evening consumption may benefit from different settings to someone who uses most of their electricity during the day. The right approach can also change through the seasons as solar production and household usage change.
Want some help with your setup?
Clifford from Solar Wholesalers can help you understand your system, app and electricity plan, and work through settings such as grid charging, time-of-use operation and sensible charge rates.
The goal is simple: set the system up properly, understand what it is doing, and let it do the work for you.
