What are your needs?
This is perhaps the most critical step in the entire process of implementing an off-grid-capable power system. While many may be tempted to guess their way through this part, or wing it, don’t do it. Take the time to really get to know your needs now, and you’ll spare yourself a lot of headache and expenditure. You’ll also be able to intelligently dialog with service providers, vendors, and product sales persons.
Each reader will likely have different goals. To facilitate this discussion, let’s break down needs into a few groups based on the length of time one would like to be able to power their home by off-grid means. We will use hours because many experience power outages for less than 24 hour periods, or can experience many small outages per year.
- Basic: Those who want to be prepared to be off-grid for less than 200 hours per year
- Intermediate: Those who want to be prepared to be off-grid for 200-500 hours per year
- Advanced: Those who want to be prepared to be off-grid for greater than 500 hours per year
- Premium: Those who want to be prepared to be off-grid indefinitely, or desire more complex, redundant backup power systems.
The first item to discuss is this…. you need to have realistic expectations about your needs. Not your wants, your needs. You may add on to your capabilities as time and resources permit later on, but the initial goal is to handle your needs. Needs might entail running a well pump, or keeping a refrigerator or freezer on to keep food from spoiling. Hair dryers, microwaves, and video game consoles are not needs.
With your needs in mind, your first assignment is to identify your needs. Write them down on a piece of paper. Review them, double-check them. If you’re uncertain about what these needs are, you might consider turning off your main circuit breaker panel (see footnote #1), then for the next few hours, take note of what you really need to have functional when no power is available.
For average families, this might entail things such as:
- Well pump
- One or more outlets to charge devices such as phones and radios
- Sump pumps
This list is your ‘critical loads’ which must remain powered during an off-grid scenario.
Tip: Obtain some colored dot stickers (perhaps red) and place a sticker next to each circuit breaker in your electric panel that is responsible for providing power to your critical loads. This will assist you later on in your implementation of an off-grid-capable power setup.
Resist the resistive!
“Resistive loads” are electrical appliances, devices, or circuits that create heat by using resistance. Any electrical appliance that produces heat is a resistive load. Hair dryers, microwaves, space heaters, toasters and toaster ovens… these are all resistive loads.
It is not advisable to count any resistive load as a critical load as they consume a tremendous amount of power and doing so off-grid will be difficult and expensive. Don’t worry – we can help you find other ways to provide some of the functionality these appliances provide (see footnote 2)!
Next, comes the math
Don’t be scared here… you can do this next part with elementary school mathematics…
You need to understand how much power is consumed by your critical loads. What you’re aiming for is to discover the average watts used by each appliance or circuit in a 24 hour period of time.
There are a few ways to do this…
Most appliances have some sort of ‘nameplate’ affixed to them (or in their manuals) that displays the appliance’s ratings. These will be marked with “amps”, “volts” and “watts”. watts are a measure of power that is calculated by multiplying amps times volts (A x V = W).
Multiply the watts used by the number of hours the appliance will run in a day. This is ‘watt hours’. Write this number down for each appliance or device as “Avg watt hours per day: ____”.
Note: Though plugged in for 24 hours a day, an appliance isn’t necessarily running for 24 hours a day. For example, a fridge or freezer may come on for a few hours of run time per day, despite being plugged in and ‘on’ all the time. If the freezer consumed 100 watts and ran for three hours, you would write down 300 watt hours.
Total all of the ‘Avg watt hours per day’ for each device or appliance. Write this down as “Total watt hours per day: ____”.
Along with knowing the total watts consumed per day, you also need to know the peak amount of wattage used at any given time. Many appliances require more watts when starting then when running. If multiple appliances or devices were to start at once, the power required would be the sum of all of the maximum wattage of each starting appliance or device. Some appliance nameplates make this distinction. If not, assume the watts calculated is the peak watts.
You need to know the total peak wattage that will be required by the sum of all your running critical loads. To fudge this, you might consider adding the wattage of all your critical loads together and writing down this number. This may be unrealistic to assume that all devices would start at once, but it can and does happen when switching to off-grid power. Using this sum plus 10-25% for a buffer is a good number to use as your “peak wattage”.
You should now have three numbers:
- Average watts per day (per appliance)
- Total watts per day
- Total peak watts
These numbers will be critical in the process of determining your needs.
A (much) better way
If doing all this estimating is not satisfying to you, or you prefer a more elegant solution, consider one of the following approaches to get more accurate measurements of your needs.
- Kill-a-watt meter – These simple devices allow you to plug your appliance into them for any period of time and see the watts consumed in that period. These offer a much more precise view or your power consumption. The longer you monitor the appliance or device, the more accurate of a measurement you’ll receive.
- The Energy Detective (TED) – Slightly more complex, TED attaches to your main breaker panel and provides very detailed analysis of your power consumption. The main advantage of the TED for our purposes is seeing the peak wattage used. The few hundred dollars for TED is a worthy investment and could save you thousands of dollars by not purchasing more off-grid-capable power equipment than is necessary. Additionally, statistics show that most people who begin to monitor their power consumption tend to reduce their consumption as a result, thus saving money.To calculate true peak wattage of your critical loads, install a TED, then turn off all circuit breakers that are NOT critical loads. Keep these non-critical loads off as long as you’re able (up to 24 hours) and take note of the continuous wattage and peak wattage reported by TED. This is the most precise means of measuring critical loads needs.
- Many professional electricians might caution against cycling your main circuit breaker because the main breaker may have not been exercised in many years, could be corroded, and might not function properly when attempting to turn the power back on. Do so at your discretion.
- Can you run your entire house off-grid? Yes, it is possible. Just be prepared to spend significant resources to keep those resistive and non-critical loads running off-grid.