Want a home battery on a budget? Consider a portable, DIY system.

A whole-home battery, wired in by an electrician, usually costs at least $15,000. If that's out of reach or you rent, a portable power station is a cheaper, plug-and-play alternative. These battery boxes range from toaster-size to carry-on-size, cost a few hundred to a few thousand dollars, and recharge from a wall outlet, a car, or portable solar panels. They're sold at Best Buy, Costco, and Home Depot, among other retailers. During an outage they can run a fridge, Wi-Fi router, phone, laptop, window air conditioner, or CPAP machine. Some models also use an app to charge up on cheap off-peak electricity and discharge during expensive hours, trimming your bill even when there's no outage.

Before buying, list what you'd want to power and add up the watt-hours you'd need for as long as you'd need them — an online worksheet can help with the math. Storage capacity ranges from about 500 to 4,000 watt-hours for most portable units, though some can be expanded much larger. Worth checking on any model: lithium-iron-phosphate battery chemistry (safer and longer-lasting), at least a one-year warranty, a "pure sine-wave" inverter (needed to safely run sensitive electronics), and whether it can charge while powering a device at the same time.

Newer, two-way models that can send stored power back into a home's outlets are starting to arrive in the US, but so far only in Utah and Maryland, two states that have legalized this kind of home solar and battery setup. Whether your state allows it is worth checking.