Many people mistakenly mix up power and energy, which are two different, but related concepts. It is critical for people going off-grid to understand these concepts, and selecting proper equipment is done by understanding and agreeing upon the power and energy needs for the home.

Power

The instantaneous amount of electricity all of the appliances and devices in your home are using. If you have five 100W light bulbs on plus a 1,500W water pump, you are using 2,000W of power. Power is measured in watts, or kilowatts (1,000 watts per kilowatt).

Energy

Energy is power over time. If you use a 100W light bulb for twenty hours, you will have used 2,000 watt-hours. Similarly, if you use a 2,000W water pump for 1 hour, you will have used the same 2,000 watt-hours. Energy is measured in watt-hours, or more commonly kilowatt-hours.

Why Does It Matter?

Some equipment is sized based on power needs, and some is based on expected energy usage. Other equipment needs to take both power and energy into account. We will get into this as we explain the different components required in an off-grid solar energy system.

Side note: if you plan to use 100W light bulbs in your home, off-grid living is NOT for you!