What's a Power Wall And How Do They Work?

April 27, 2022

A Battery For Your Home

Electric cars are just one part – if a significant one – in the world’s move to more sustainable energy. There are interesting things happening with electricity off the road as well. One of the most interesting developments of recent years is “power walls,” energy storage systems for homes that are typically connected to solar panels.

A power wall is basically a battery for your home, that can power all of your appliances, electronic devices, lights, and anything else requiring electricity – which, as we know when the power goes out, is almost everything! The basic lithium-ion technology of a typical power wall is almost exactly the same as you’d find in an electric car.

A power wall typically charges through a combination of drawing electricity from the grid – just like your EV would – and from solar panels. All batteries store power in DC (direct current) format, but your house runs on AC (alternating current), so an inverter is needed, and often included as part of a power wall, to convert incoming electricity from the grid. Solar panels produced DC power, and can thus be connected directly to a power wall – or run through your home’s AC system through rectifiers (which convert DC to AC) and inverters (which convert current back to DC to be ingested by the power wall).

Save Money, Increase Security

Why would you want to have a power wall and still draw electricity from the grid? For two reasons – cost and security.

Most electrical providers charge different rates at different times of the day, with peak usage times like the early evening costing the most. A power wall can fill itself up during off-peak hours, where electricity is cheapest, and then power your home during peak hours.

Connect your power wall to solar panels, and you can save even more. With solar panels or roof shingles, you can fill up your power wall with solar power, further reducing what you draw from the grid. The combination of using off-peak electricity and solar can greatly reduce your energy bills and cover a large part of your electricity consumption during day and night.

A power wall can also provide additional security for your home during a power outage. Its stored energy means that you can literally keep the lights on, as well as the TV, radio, and other electrical devices, for several hours without interruption. Install multiple power wall units in your house – it’s just like adding batteries – and you may be able to go for a day or more.

Power walls are available from a number of companies. Tesla is probably the one you’ve heard of, but Enphase and Generac also make them, among others. Most single units have a storage capacity in the range of 10-15 kWh, a fraction of what an average electric car battery holds – but a power wall doesn’t need to push your house down the road. 10 kWh is enough to power the average home’s needs for several hours independently, and you can add additional units to expand capacity. Pricing ranges from $10,000 to almost $20,000 per unit depending on manufacturer and specifications, with pricing per unit coming down the more units you order.

Hyundai has also announced a concierge service called Home, which will help EV buyers get a home charger, solar panels, all rolled into one convenient payment. A package could include rooftop solar panels and a power wall.

How To Get Hooked Up

While the batteries themselves are not complex technology, getting them properly connected to the grid, and especially a solar system, requires a trained professional, and cost for installation can vary widely depending on your home’s existing electrical infrastructure.

Could you charge your electric vehicle from a power wall? The short answer is yes – but you wouldn’t be getting much of a charge. With 10-15 kWh of capacity, a single power wall unit would only give your EV a small amount of extra charge, or range, before emptying itself – EVs require a lot of power to move, and typically have batteries ranging from 40 to over 100 kWh!

In fact, the reverse situation might be more common – an electric vehicle with a big battery could be used to top up your power wall in an emergency situation. Most notably, Ford has an “intelligent backup power” option for the long-range F-150 Lightning that can power a home for up to three days – or potentially juice up your power wall if needed.

Given that power walls work best when using a combination of the grid and solar, they probably make the most sense to install as part of a new (and sustainable) home build, or a major renovation. But regardless of how you choose to implement one, intelligent power walls are another milestone on the way to a more sustainable future.