Home Batteries

Introduction

Battery storage, from household to utility-scale batteries and within electric vehicles, is a game changer in the energy transition. Solar penetration is still low in New Zealand but it is growing quickly and if we want to make the most of it we need to capture and store it to be used when the sun isn’t shining and when demand is at its highest.

With the cost of batteries falling rapidly and the performance rapidly improving, getting a battery could be a key piece of the puzzle to untether yourself from fossil fuels. Whether you're aiming to save money on electricity bills, minimise your carbon footprint, or prepare for emergencies, now is the time to consider investing in a home battery.

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Why choose a home battery?

• Reduce running costs. Reducing the energy you import from the grid - especially if you are on a time of use plan during the peak tariff periods (eg. 7 - 11 am or 5-9pm) when there is high demand could reduce your energy bills significantly if you have solar. Battery cycles are now cheaper than grid electricity, and if it can be financed at a low interest rate through a green loan then it is likely already affordable today for many homes. 
• They’re great for the climate. Maximising renewable energy resources by storing it for use at night time or during periods of low solar production ensures a significant reduction in household emissions.
• They improve resilience. Whether it’s to use energy during blackouts or extreme weather events, batteries can provide you with power when there is a grid outage and can be charged via rooftop solar.   
• ‍They’re important for our energy transition. With solar and battery storage, households can become a key part of our energy infrastructure. Every home with a battery is basically removed from the peak load, can add security during blackouts and reduce the need for expensive large-scale infrastructure. Batteries in homes and businesses may seem individually small, but they could have a significant impact when combined. As an example, 120,000 homes (or 5% of households in New Zealand) with a medium-sized battery could potentially reduce the peak load as much as our largest hydro power station, Manapouri. While these batteries would not hold as much energy as Manapouri, they could output the same amount of power for an hour or two when the system really needs it.

What to consider ?

• Compatibility: If you are buying solar at the same time, opt for an inverter that is compatible with both systems. If you have an existing solar system, depending on your current inverter, you may need to purchase a new one.
• Battery location: You have to follow New Zealand Standards as to where they can be placed, which will be known by your installer. 
• Your location: The amount of sunlight hours will affect charging rates. If you live in a cooler climate you most likely will need a larger battery as your solar production will be lower. If you live in a hot climate, make sure the battery is shaded so as not to overheat. 
• Controllability: Consider choosing a battery that can be easily controlled by yourself or can be automated to charge and discharge to maximise its use.
• Battery chemistry: While lead-acid batteries used to be popular, especially in remote areas, the most widely available home batteries use lithium-ion chemistry (similar to the batteries in laptops and mobiles) because they are more efficient and have higher power for weight/volume. There are sub-types of lithium ion batteries with variations in efficiency and capacity so it’s best to discuss with your installer. Nickel-iron or flow batteries can’t compete on performance and price; while sodium-ion batteries also can’t currently but may do so in a few years.
• Capacity: To determine battery size, calculate your electricity usage and power of appliances, aiming to cover energy consumption during peak grid times (eg. 5-9pm). Also factor in future usage, such as replacing gas appliances with electric ones. One day we may all have big batteries on wheels parked in our driveways (otherwise known as electric vehicles) that can power our home, but only the newer, more expensive models offer that at this stage.

Renters

Unfortunately, asking for a battery from your landlord is challenging. Our advice is to first pitch having solar panels installed as the return on investment is just 5 -7 years on average, making it an easier sale. Join advocacy campaigns, such as with Rewiring Aotearoa, which is calling for the government to do more to make electrification accessible for renters and incentivise landlords to install solar and batteries with low interest finance that could reduce tenants' bills, improve the appeal as a rental and increase the value of the property.

FAQ