How can you tell if something is energy efficient based on watts and volts?

Question

I live in a van and have only a certain amount of energy I can use each day but can never tell what appliances are efficient or not. HELP

In: 1

Answer 1

You need to compare X to Y and take the thing that uses less watts for the same result.

Heating is always going to use lots of energy. For instance, you want to make a cup of tea.

You need to take 200g of water from 27C to 100C.

+1C per 1 gram of water = 4.18 Joules. 4.18 * 200g * +73C = 61028 Joules.

1 Joule is 1 Watt for 1 Second, so 61k Joules to heat your water would take a 1kw Electric kettle, 61 seconds to boil and use 1kw for 61 seconds of time. 1kw @ 230v pulls 4.3 amps.

Now lets put that into perspective, what does 1kw for 61 seconds (61kJ) look like for a cup of tea.

1, 100 w incandescent bulb could be lit for 10 minutes with the same energy.

1, 13w LED bulb (100W incandescent equiv) could be lit for 1 hr 15 mins with the same energy.

1, 21 inch box fan could run for 12 minutes with the same energy.

For heating things, charcoal briquette come in at around 8kJ/g, meaning burning 10 grams of charcoal, which is less than 1 single briquette, would produce more energy than needed to boil your 200g of water. You may want to find some kind of mini-fire stove to heat shit and not use your power for heating. Save it for light and motors which require it.