EV CHARGING
Can you charge an electric car from a home battery?
Charging an electric vehicle with a home battery is technically possible, but in most cases the battery is too small to fully charge the car.
A typical EV battery is much larger than a home battery, so home storage is usually better suited to adding some extra range rather than providing a full charge. How useful it is also depends on the capacity of your home battery, its power output and the size of the battery inside your electric car.
QUICK ANSWER
A home battery can charge your EV, but usually only partly
An electric car typically needs around 40 to 80 kWh for a full charge, while an average home battery may have around 5 to 15 kWh of storage capacity. This means a home battery can add useful driving range, but a full EV charge is usually not realistic for the average household.
BATTERY SIZE
Why a home battery cannot fully charge most electric cars
The main reason is the large difference between the capacity of an electric car battery and the capacity of a typical home battery. An electric car usually needs much more stored energy than an average household battery can provide.
ELECTRIC CAR
40–80 kWh
Typical EV battery capacity
An electric car can require around 40 to 80 kWh of electricity for a complete charge, depending on the model and battery size. Smaller electric cars may be closer to the bottom of this range, while larger EVs can have considerably bigger batteries.
This means that charging an EV from empty to full requires a large amount of electricity compared with normal household appliances.
HOME BATTERY
5–15 kWh
Typical household capacity
A typical residential home battery is much smaller. A system with around 10 kWh of capacity may be a useful size for storing solar electricity and supplying normal household demand, but it only contains a fraction of the energy stored inside most electric cars.
This is why a home battery is usually better used to add some extra EV range rather than trying to provide an entire charge.
Around 12.5% to 25%
A full 10 kWh home battery could theoretically provide around 12.5% to 25% of the capacity of an EV battery between 40 and 80 kWh. In practice, the amount that reaches the vehicle will be slightly lower because some energy is lost during charging and conversion.
A home battery can therefore still help you charge your car and potentially reduce how much expensive grid electricity you need, but relying on the battery alone for a full EV charge is unlikely for most households.
CAPACITY COMPARISON
How much can you charge your EV with different battery capacities?
A larger home battery can provide more energy to your electric car and therefore add more driving range. The table below gives an indication of how much different home battery capacities could contribute to EV charging.
| Battery capacity | EV charging percentage | Driving range | Remark |
|---|---|---|---|
| 5 kWh | 7.5% | 25–32 km | Suitable for a small home battery setup. Adds only a relatively small amount of charge to most EVs. |
| 10 kWh | 15% | 50–65 km | A common size for an average household. It can add useful driving range, but is far too small for a full EV charge. |
| 15 kWh | 20% | 75–100 km | Suitable for households with higher electricity use. It can provide around 20% of the capacity of a typical EV battery. |
| 20 kWh | 30% | 100–135 km | A larger home battery system, often more suitable for homes with high electricity use, solar panels or a heat pump. |
| 30 kWh | 45% | 150–200 km | A very large residential battery that could provide a significant part of an EV charge. |
| 40 kWh | 60% | 200–275 km | A very large home battery capacity, similar in size to the battery found in some smaller electric cars. |
| 60 kWh | 85% | 300–400 km | Much larger than a typical residential battery system and close to the capacity of many modern EV batteries. |
| 80 kWh | 100% | 400+ km | Large enough in theory to provide the equivalent of a full charge for many EV batteries, although charging losses mean not all stored energy reaches the car. |
The percentages and driving ranges are indicative. The actual result depends on the battery capacity and efficiency of both the home battery and the electric vehicle, as well as the vehicle’s energy consumption.
CAPACITY VS POWER
Does the power output of your home battery matter?
Capacity is not the only thing that matters when choosing a home battery for EV charging. The power output is also very important. These two figures are related, but they tell you something completely different about the battery.
CAPACITY · kWh
How much energy can be stored in the battery?
Capacity is measured in kilowatt-hours, or kWh. It tells you how much electricity the battery can store in total. A 10 kWh home battery can therefore store roughly twice as much electricity as a 5 kWh system.
When you want to use a home battery for EV charging, capacity determines how much energy is potentially available to transfer to the vehicle.
POWER · kW
How quickly can the energy be delivered?
Power output is measured in kilowatts, or kW. It determines how quickly the electricity stored inside the battery can be supplied to your home or electric car.
A battery may have plenty of storage capacity, but if its power output is relatively low, transferring that energy to an EV can still take a long time.
A SIMPLE EXAMPLE
80 kWh / 2 kW = 40 hours
If an electric car needs 80 kWh for a full charge and the battery can supply 2 kW continuously, it would take around 40 hours to deliver that amount of energy. A system that can deliver 5 kW would be able to transfer the same amount of energy much faster.
This is why looking only at the number of kWh can give an incomplete picture. If EV charging is important to you, compare both the storage capacity and the maximum power output of the home battery.
SOLAR EV CHARGING
Is it better to charge your EV directly from solar panels?
Charging your electric car directly from solar panels is usually more efficient than first storing the solar electricity in a home battery and then transferring it to the EV.
DIRECT TO YOUR EV
The most efficient way
If your solar panels are producing enough electricity during the day and your car is at home, it usually makes sense to send as much of that solar electricity as possible directly to the EV.
The electricity can be used by the car without first being stored and discharged by a separate home battery. This avoids an additional charging cycle and therefore reduces the amount of energy lost during the process.
VIA YOUR HOME BATTERY
More flexibility, but more conversion steps
When solar power is stored in a home battery first, the electricity has to go through an additional charging and discharging cycle before it reaches your electric car.
Every time electricity is stored and converted, a small amount of energy is lost. This makes direct solar charging more efficient when your EV is available during sunny hours.
A home battery is useful when your car is not at home
Direct solar charging is not always possible. If your car is away from home during the day, your solar panels may generate their highest output when there is no EV available to use it. A home battery can store part of that surplus electricity so it can be used later when you return home.
A LARGER BATTERY
Is a larger home battery worth it if you own an electric car?
A larger home battery can be worth considering if you own an electric car, but it depends on how much electricity your household uses, how much solar power you generate and how often you charge your EV at home.
An electric car can add a significant amount to your annual household electricity consumption. This means a battery that would normally be large enough for your household appliances may become relatively small once regular EV charging is added.
MORE SOLAR PANELS
Store more surplus solar power
A larger battery can be useful if your solar panels regularly generate more electricity than your household can use during the day.
Instead of sending a large part of this surplus back to the grid, you have more storage space available to keep it for later.
HIGHER ELECTRICITY USE
An EV increases household demand
Regular EV charging can significantly increase your total electricity use. A small home battery may therefore only cover part of your normal household demand before you even start charging the car.
A larger system gives you more flexibility to divide stored electricity between your home and your electric vehicle.
CHARGING FROM HOME
More capacity for regular charging
If you regularly charge your electric car at home, having more storage capacity means more electricity can be saved during the day and used later for either your household or your EV.
This can be especially useful when your car normally arrives home after your solar panels have stopped generating most of their electricity.
WHEN DOES IT MAKE SENSE?
A larger battery makes the most sense when your electricity demand is also higher
A larger home battery is particularly interesting if you have many solar panels, high household electricity use and regularly charge your electric car at home. In this situation, the additional capacity gives you more opportunity to store surplus solar electricity instead of sending it back to the grid.
However, buying the largest battery available is not always the best option. The system should still be matched to your actual electricity use and solar generation. You can compare different home battery capacities or use our home battery configurator to estimate which size is most suitable for your household.