Buying a giant battery for the next blackout or off-grid adventure can be daunting, especially when hundreds or even thousands of dollars are on the line. Get it wrong and youâve either spent too much money for something youâll never use or discover that you didnât buy enough capacity to keep your most important devices running. To get it right, you need to become intimate with the watt-hour (Wh).
The watt-hour is a measure of capacity, or how much electrical energy a battery stores. If you know how much power â measured in watts â your devices consume, then the Wh rating of a battery lets you quickly calculate how long those devices will run. For example, a typical LED light bulb requires about 10W to illuminate. So a 1000Wh (1kWh) battery can run that bulb for 100 hours because Wh divided by watts gives you the time.
For context, the average US home consumes about 889kWh per month, or about 29.2kWh per day, according to the US Energy Information Administration. During a blackout, youâd need about $15,000 worth of batteries on hand to keep it running for just one day (based on a rough average of 50 cents per Wh of battery capacity). But thatâd be silly because you …
