Battery Storage FAQ
All your questions answered
The capacity of a battery is the total amount of charge that it can deliver, and it is expressed in the units of kilowatt-hour or kWh.
kWh is also the commonly used by the electricity meter in your home. This makes it easy to calculate how many kWh you use on an average day, and size your solar and battery system accordingly.
Some batteries are sold using their “total capacity” and some quote the battery’s “usable capacity.”
A battery should never be fully drained, therefore there is a certain amount of capacity that cannot be accessed. As an example, a Tesla Powerwall 2 has a total capacity of 14kWh however it’s usable capacity is 13.5kWh.
Always ensure that you check a battery’s usable capacity, to ensure you are comparing and sizing systems equally and correctly.
All battery storage systems will have a maximum amount of power they can deliver at once. This will vary massively depending on the system you choose, and can make a big difference to the way your battery is used.
If a battery is only capable of delivering 1.5kW, and you use turn on a 2kW kettle, then any extra power requirements will need to be drawn from the grid.
Some battery packs will have a maximum constant load, and a higher maximum load for short (peak) periods. Check the power output before you buy, otherwise you may find yourself drawing a lot of energy from the grid, even when you have energy in your battery.
A cycle is one complete discharge and one complete charge. Most of the time a battery does not operate like this. It may discharge by 20% and then recharge any number of times.
A 25% discharge and charge would count as one quarter of a cycle.
Batteries are often rated on the number of cycles they are warrantied for. This can be a good indication of the long-term performance of the battery. We are happy to discuss any technical elements of battery storage if you have any questions.
Yes, your FIT payments and export payments will still be based on your actual solar production as shown on your generation meter. Your export payments are based on an estimated figure of 50% of your generation, and this is unaffected, even if the battery storage system means you are consuming 100% of your produced electricity.
If you have a battery storage system connected on the DC side of your solar pv system (ie: before the generation meter) this will slightly reduce your generation meter figure and subsequent FIT payments, by the efficiency of the battery storage conversion process.
If possible, it is best to store and use as much of your own power as possible. Not only does this guarantee that carbon-free green energy is used but it also allows you to maximise your savings financially, which is where the real gains lie with a solar pv system.
Current home battery storage systems come with warranties as long as 10 years but are likely to continue to provide usable capacity for much longer.
Lithium-ion batteries are designed to be continuously cycled and are lasting much longer than early models predicted. The battery packs in electric cars use the same technology, and there are vehicles that have covered over 150,000 miles over many years with minimal battery degradation.
Old style lead acid storage systems could be bulky and unsightly. A modern lithium-ion battery storage system such as a Tesla Powerwall 2 or LG Resu has sleek looks and requires no ongoing maintenance.
Systems can often be installed either inside or outside depending on space requirements and aesthetic preferences.
Home battery storage can be easily be integrated in to an existing solar system.
By adding battery storage to your Solar PV system you will be able to make the most of the power you generate. You can enjoy the benefits of your free solar electricity all the way through the night until the sun rises.
If you have an older system you may need to upgrade your inverter to one with battery storage capabilities. Please get in contact if you have any questions about integrating with an existing Solar PV system.
Yes, current lithium ion batteries are almost completely recyclable. They can either be broken down and rebuilt in to new batteries or they can be used for another purpose. .
If a battery storage system is professionally installed and used correctly then it is perfectly safe. Battery storage does not provide a higher risk than any of the other electrical devices in your home.
Installing battery storage in your home does not guarantee that you can disconnect completely from the electrical grid.
Depending on your household electrical demands and the amount of power you can generate through solar/wind it may be possible to go off-grid. Not all battery systems are designed to do this. If you are considering going off-grid, we recommend looking through our off-grid information, and then getting in contact to discuss your options.
No, you can often charge your battery by any source including the grid, wind, or hydro.
Typically, battery storage is used in conjunction with micro-generated renewable sources (solar, wind, hydro) however it can be used to store power from the grid at cheap, off peak times to be used during expensive, peak periods.