Updated 2020

This article explains that energy and power are different concepts. Confusing one for the other will mislead with solar & batteries and many other areas. Here’s why and how.

Power is a measure of how quickly energy is used

Weightlifters like Svetlana Podobedova (above) readily lift huge weights. Doing so demands extreme power. A child can readily lift the same in smaller amounts. This needs little power but the energy used is the same.

Some batteries are promoted as producing massive power. They may well do so. But in say, caravan, motorhome and solar use it’s mostly energy, not power, that matters. Here’s why, and how you can save a lot of money by knowing this.

How confusing these terms can matter

Energy relates to work done. Power relates to the speed at which energy is expended. 

Surprisingly little energy or power is needed to hand start a car engine. Pic: reproduced here by courtesy of the Henry Ford Museum (copyright Henry Ford Museum).

Why confusing these terms can matter 

Much of the time, confusing the two terms does not matter. Where it can do, however, is in battery advertising re caravans, motorhomes and solar. Many battery vendors either do not know the difference, or deliberately deceive. They promote their products’ power in areas where power does not matter. For example, the only product in such areas that need a lot of power is a microwave oven. It typically needs 110 amps (at 12 volts). But any 12 volt battery bank over about 250 amp hour will do this.

Our books: Solar That Really Works cover cabins and RVs. Solar Success covers homes and properties. The associated Caravan & Motorhome Electrics covers every aspect of RVs in depth. Our all-new book – Why Caravans Rollover – and how to prevent that is rapidly becoming a top seller.

Please also see also our associated website: rvbooks.com.au