How To Calculate Power Consumption
Figuring out how much power you consume is important for creating your energy system. You’ll need to understand your power needs, so you don’t fry your devices.
Having this knowledge even if you don’t plan on making an energy system at the moment, when SHTF you’ll want to know this so you can find the parts needed to run your essentials.
When you’re figuring out your energy needs start with your major appliances such as your fridge, microwave, chest freezer, etc. You’ll need to calculate the watt-hours, amp-hours, and the voltage. Don’t worry I will walk you through on how to do this and what each of them mean.
Now for some basics of electricity.
In order to calculate your power consumption, you will need to know some of the terms and equations involving electricity. To help you understand I will use analogies between the electricity terms and a river.
Ampere- Aka Amp or current is the unit of measure for electrical current. In the equations Amp = “I”. Think of amp as the amount of water flowing down a river.
Ohms- Is the unit for electrical resistance in a conductor. Ohm is like the opening or narrowing of a river, the more open the easier for the water to flow through, vice versa for the narrowing of a river. Generally, to find voltage is to use Ohms Law that says volts = amps x resistance.
Volts- Is the unit for electrical voltage. Voltage is the amount of water pressure flowing down a river, the more volts the faster the water is flowing.
Watt- AKA power is the rate of electrical energy. “P” is used in the equations. To keep on with river analogy this is the amount of water flowing through a river. Also, most things are shown as Kilowatts to find the wattage you would multiply the kilowatt number by 1000. 1kw=1000w
Now for some equations related to those terms. To find the voltage you would use ohms law which is V=IxR and to find the watts or power you would use P=IxV.
So how do we use these to calculate our power usage? We convert them into watt-hours and amp-hours.
Watt Hours- AKA Wh is a unit of energy that measures watts over a period of time in this case hours. If something is rated at 100w (watts) that means it uses 100w an hour, so if it has been running for 3 hours it has used 300w. So, Watt Hours = Power Over Time.
For example, if you want to calculate how many watts a 60w light bulb uses in a day, the equation would be 60w x 24 hours, which comes to be 1440Wh.
The equation for this is (total watts) x (total hours) = watt-hours.
Amp Hours- AKA Ah is the measurement of current flowing over a period of time. It gives you the number of amps your electrical device is using over the period of an hour. This is important to know when determining how many and what type of batteries you’ll be using. So, Amp Hours = Current Over Time.
For example, when using a 100Ah battery it can disburse up to 100 amps of energy an hour and 200Ah after 2 hours.
It is vital that you know how to convert each of these from each other and how they are different.
To get watt hours from amp hours you would use this equation: Wh=AhxV.
To get amp hours from watt hours you would use this equation: Ah=Wh/V.
There are some devices you could use to determine the watt hours and or kilowatt hours. These are Power Meter Plugs that you plug into an outlet or power cord, and then you plug your electrical component into it. I have tested a few different ones off of Amazon and found this one to be the best.
This device has the functions to show you the watt hours, kilowatt hours, and amp hours.
Now on to tying this all together to calculate your power consumption, in order to know the size of the energy system you will need to live off grid and to keep your power going through a SHTF situation.
- Make a list of each appliance and electrical device you have as well as the number of watts for each.
- Estimate the amount of daily use for each. (The number of hours they are used in a day)
- Multiply the watts by the number of hours used to get watt hours.
- Add all the Wh together.
- To get the amp hours divide the total Wh by the number of volts.
Here is an example table of some electrical devices. This is an example only and may not match what you have.
Here is my excel worksheet that can help you with figuring out the Ah as long as you have wattage. It is locked so the formulas don’t get deleted but you can unlock it to add more cells if needed.
Now if you want to check out your whole houses energy consumption it should be displayed on your electric bill. I just checked mine and it said I used about 1200KWH which converts to 1,200,000Wh. My house has a 240v system so the amp hours would be 5000Ah. This was for February, so winter causes higher energy usage. There are more precise ways to measure that I will put a post about in the future.
All these numbers will be important when figuring out how many batteries you will need, the size of battery, and even the gauge of wire required to run your system and to not fry anything in your house or worse cause a fire. We will discuss what you’ll need in terms of energy generating devices in the next post.
These are the basics on how to calculate power consumption, I hope you found it informative and if you have further questions feel free to leave a comment and I’ll reply ASAP.
Don’t worry my next blog post will put all this together and we will figure out your required energy system!
I do need to let you know that the Amazon link is an affiliate link and purchasing through it I do make a small commission.