Determining Home Backup Power Needs
July 20, 2023
A backup power system can help keep essential appliances and devices powered up when the electric grid goes down. Choosing a solution that can support vital circuits in your home, plus a few conveniences, is important. How do you determine how much backup power you need?
Begin by listing the things you want to power during an outage. For example: refrigerator, freezer, lights, fans, water heater, well pump, etc.
Look for the power ratings of each item on their labels or user manuals. Alternatively, use online sources to find typical wattages or the wattage of specific products.
Power ratings are typically measured in watts (W). If only amps and volts are provided, you can calculate the power using the formula: Power (W) = Voltage (V) x Current (A).
Some devices have a constant power draw, while others vary depending on their settings or usage. Identify the power consumption of each item during normal operation or the power it consumes when running continuously.
Some appliances, such as refrigerators and air conditioners, require an extra surge of power to start up before settling into their normal running power. This starting power is typically higher than the running power and lasts for a few seconds or minutes. Find the starting power rating for these devices. It may be listed separately or as a peak or surge power rating.
Add up the running power of all the items to get the total running power required during an outage. Similarly, add up the starting power of devices with a surge requirement to get the total starting power required.
Determine the probability of multiple devices starting simultaneously. Account for the combined starting power of those devices when sizing your backup power solution.
Based on the total running power, total starting power, and a 20% safety margin, look for a backup power solution that can handle those power requirements. Generators are typically rated in terms of their running power (continuous power output) and their starting power capacity. Select a generator or battery backup solution that meets or exceeds your total starting power requirement to avoid overloading.