Introduction: Solarpunk Math! How to Figure Out Electrical Loads for Theme Camps

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About: Careers: documentary filmmaker, DOP, engineering student, practical environmentalist, idealist. Loves: bicycles and when weeds grow in the city. I'm from western Canada, Yukon, Japan and Montreal.

So how much electricity does my theme camp actually use? No idea? Let’s make it easy 🤩

We're going to learn the wattage of your devices, multiply this by the number of hours each device is active, and tally up the watt-hours.


When you’re done here, head on over to a more detailed guide with tips on using e-bike batteries and e-cars as ‘free’ portable batteries. https://www.instructables.com/-Solar-Power-at-Burning-Man-or-Just-Camping/


We’re going to make an electrical budget. It’s almost the same as a financial budget.


Let’s go!

Supplies

First a couple of tips to get the most bang for your electrical buck.


  • A Kill-A-Watt or similar amp-hour meter will tell you how much electricity you’re actually using over time. Go get one now. It’ll tell you more details.
  • Music at full blast uses an average of 1/10th of what it says on the loudspeaker. Your 10,000w subwoofers use an average of 1000w.
  • Things whose main job is heating up or cooling down use a lot of electricity.
  • LED lights are like 10 times more efficient than incandescent lights.
  • Incandescent lights are usually glass and hot to the touch.

Step 1: Let’s Make a Budget!

Let’s list three criteria:

  • What are we running?
  • What is its wattage?
  • For how many hours?


For example:

Blender, 900w, 1/2h run time per day.

LED Christmas lights, 5w, 10h per night.

Music, 1000w speaker, 13h per day. (Remember to divide by 10 for music)


Now multiply each item’s watts times its hours of use. This gives you watt-hours:

Blender, 900w X 1/2h = 450watt-hours.

LED Christmas lights, 5w X 10h = 50watt-hours.

Music, 1000w/10 X 13h = 1300watt-hours.


Tally up your total watt-hours:

blender 450wh

+ lights 50wh

+ music 1300wh

= total 1800 watt-hours per day.

If you’re using a battery, this will tell you how big a battery you’ll need for a day’s work (plus some buffer depending on the chemistry)

Note, three or four ebike batteries will run this camp for a day, an electric car will run it for many days.


Also tally up your peak wattage:

blender 900w

+ lights 5w

+ music 1000w

= total 1905 watts

This will tell you the maximum amount of watts you could demand from your electrical supply. Without getting too far into the weeds, this is the number you’ll want on your inverter. Or this is the number to tell someone who’s supplying you grid power.


For fun, calculate how many watt-hours get vampired away when three strings of 100watt little dim red incandescent Christmas lights get left on for 24hours.

3 X 100w X 24h = ?watt-hours

Bonkers!🧛‍♂️ Many camps have a dedicated Buffy to slay these vampire loads!


That's it, we’re done… Sort of.



Wait! WTF’s a watt you ask?

Step 2: WTF’s a Watt!?

Where do I find a device’s wattage? There’s a handy electrical ‘price tag’ on all devices. Look for a tag on the cable or on the back of the device near where power cord goes in. This will tell you amps or watts.


For things that plug into the wall, if the tag says amps, multiply this number by 120 volts to get your wattage.


If the tag says both watts and amps but the numbers don’t make sense… Like if 120v times the rated amps is different from the rated watts, the bigger number is the peak load. Often things with motors will draw lots of electricity for less than a second when they start up.



Watts are how much electricity you’re using at any one time.


Watt-hours are like dollars in the sense that you pay your electric bill in watt hours. It’s the total amount of electricity you used.


Now let's explore some details.

Watts are volts times amps.

Car batteries are 12volts.

Wall sockets are 120volts (in Canada/US).

USB is 5v.

USBC puts out a variety of voltages.

Ebike batteries are usually 36v ~ 48v.

Ebike batteries can use a 12v voltage converter to work with an inverter or direct 12v DC loads.

Volts are like a baseline and they pretty much hold steady.

Amps are how much electricity your using at any given moment.

Batteries contain a total number of watt-hours but they’re often rated in amp-hours. To get your battery’s watt-hours, multiply the battery voltage by amp-hours.


Get it? Got it? Good!


Not so much? Ask your Renewables For Artists Team (RAT) for help. We do this all the time and we’re here to electrify your dreams ⚡️❤️


Want to go deeper? Try this https://www.instructables.com/-Solar-Power-at-Burning-Man-or-Just-Camping/