With electricity costs Increasingly, home batteries have never looked so attractive. Whether you want to store the excess generated by your solar panels or buy electricity at the cheapest price to use later when electricity is most expensive, a home battery can help. Installing a home battery has never been easier, but this rapidly expanding market can be confusing, and there are many things to consider before buying.

I’ve spent months researching home batteries, talking to people who use them, and then installing them myself, and I have tips for anyone interested in getting their own home battery.

Why would you want a home battery?

There are several reasons why you might want to invest in a home battery, and they are not mutually exclusive:

• You want to store excess electricity from your solar panels.
• You want to live off the grid.
• You want to avoid power outages.
• You want to buy electricity at a cheap rate and store it for later use.

Home batteries are a win-win, potentially benefiting power companies as well, as battery storage is an integral part of grid balancing and can help manage and exploit intermittent power generated from renewable sources (solar, wind, wave).

How do home batteries work?

Photo: Simon Hill

A home battery is like a giant power bank for your home. But instead of lithium ion, they are lithium iron phosphate (LFP or LiFePO).₄), because it is safer, more durable, and less prone to thermal runaway. In other words, less likely to overheat and burst into flames. There are a few manufacturers working with sodium-ion (Na-ion) batteries, which are potentially cheaper, more environmentally friendly (they don’t need lithium), and perform better in the cold, but they are also larger and don’t last as long.

Home battery technology is often similar to what you’ll find in electric vehicles. Some have even suggested using EV batteries as a home battery. But there are potential problems with that, not least finding your car battery dead in the morning. EVs are also pushing the technology toward solid-state batteries, which are smaller for the same capacity, safer because they don’t have liquid electrolytes, and last longer.

Many home batteries come in modular systems, so you can add whatever capacity you want, but they require an inverter to convert the DC (direct current) power into AC (alternating current) power that you can use. People with solar panels, or those who plan to add them in the future, should choose a hybrid inverter, which can also convert electricity from the panels for use or storage.

Inverters have different power ratings in kilowatts (kW) that indicate how much power you can draw at any given moment. Households with modest needs can get by with a 3.6-kW inverter, but that limits your continuous draw to 3.6 kW. They usually have a peak load capacity that is higher, enabling you to pull more for a shorter period of time. If you have high-demand devices like an EV charger or heat pump, you’ll want at least 5 kW, and those with high demand or large batteries will want to go higher (6 to 10 kW).

What should I look for?

There are several things to keep in mind when buying a home battery:

• Ability: Measured in kilowatt hours (kWh), it tells you how much total energy the battery can hold.
• Power output: Measured in kilowatts (kW), it shows how much energy the battery and inverter can provide at any given time.
• Discharge depth: This is how you can safely use the battery without damaging it.
• performance: This is the percentage of the power you put into the battery that you can actually use, because some energy is always lost in the storage process.
• Warranty: This is the minimum performance guarantee you can expect from the battery before it degrades (they all degrade over time), and is often expressed in years and charging cycles (whichever comes first). For example, EcoFlow promises at least 70 percent capacity after 15 years or 6,000 charging cycles.

How many home batteries do you need?

Ecoflow by Simon Hill

Calculating how much battery capacity you need can be tricky, and it depends on your use case. If you want to avoid outages or going off-grid, you should consider how much power you use over time and also the sum of your maximum power usage at any given moment to ensure that your capacity in kWh and output in kW are sufficient. If the output is not high enough, you may not be able to run power-hungry devices at the same time, so you have to think about how you will use your power.

For people like me, looking to buy cheap to use when electricity is more expensive, any capacity will do you good. But if you have a cheap six-hour overnight rate, for example, you’d ideally want it to last another 18 hours. It makes sense that you can get more since the installation costs are higher. Even later additions to modular systems often require professional installation to avoid voiding your warranty.

Do you need an upgrade or permission?

A home battery will connect to your main electrical panel via a cable, and may require some upgrading. When I installed the house battery there was no room on my fuse board, so they had to install another breaker box.

Some inverters may require permission from your electric distribution utility or local distribution company. Here in Scotland, the distribution network operator must approve your inverter, but you can install up to 3.6kW and then notify, while larger inverters require prior approval.