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Off-Grid Calculator: Size Your System for Off-Grid

If you are moving from a utility-connected home in the 'burbs' to an off-grid home in the boonies, you will have the opportunity (perhaps necessity) of downsizing your electricity usage. In order to calculate how large your home power system needs to be, run the Off-Grid sizing calculator below.

  • Run the System Sizing Calculator with with figures from working through the Load Evaluation Calculator, (PDF) based on the energy efficient lighting and energy efficient appliances you will choose for your new off-grid home.
  • Use our Appliance Electrical Consumption Table for average appliance electrical usages.
  • Decide what percentage of power you want to generate.
  • Get the daily sun hours for your building location.
  • Calculate your system size.
  • Once you calculate your system size, write it down. You will need this for Step Four.
    You can also explore some of our pre-designed systems to get a ballpark idea of what your system might cost.

1. What's the most electricity you might use in a month?

Use the actual watt-hours per day at the end of your Load Evaluation Calculator OR (PDF). You can do this by consulting our Appliance Electrical Consumption Table below or by measuring the power usage of each appliance with a Kill A Watt Meter for a more precise measurement.

* If you want a quick ballpark number, look at your past electric bills and find the month with the highest usage (often summer or winter, depending on cooling/heating needs in your area). The bill should show you the number of kilowatt-hours (kWh) used that month. Put this number in the space below.

Wholesale Solar Load Evaluation Calculator
Appliance Quantity Watts
(V x A)
Mult. * 1.5 for AC conversion
Hours On per Day Watt Hours per Day

Total Watt Hours per Day:

Watt Hours Required Assuming Inherent Efficiency Loss:

* Use these estimates to provide a general watt value for your appliances.
For example:

Blender - 500 Watts

2. What percentage of your house/business power do you want to generate with solar power?

If you want to produce 100% of your electricity, leave 100.

3. How many Peak Sun Hours do you get per day?

Enter your zip code, and we'll look up the the sun hours in your area.

Or, you can look at the Solar Map to find this number.

This gives you the annual average. If you will use your system during the winter, subtract 1.5 hours from the annual average to account for decreased sunlight during those months. This ensures your system will be properly sized to provide year-round power, even during darker months.

Sun Hours/Day

This is a very general system size estimation. Other factors such as shade, location, available panel space, and seasonal use need to be taken into account.

For the most accurate and personalized system size calculation, call our solar experts at 1-800-472-1142.

We want to help you get the system that's right for you.

Minimum System Size:
Approximate Solar Panel Wattage:

Approximate Number of Solar Panels Needed:

* For 20 Astronergy 270-watt solar panels to produce 5,400 watts..... 5,400 divided by 270(watts per panel) = number of solar panels needed.
NOTE: These figures are approximate and do not take into account the variable efficiency ratings of solar panels and off grid inverters. Please work with experienced Wholesale Solar staff to design a system which fits within your budget and can be expanded as needed.

If you want to see the results of your form submission and would like us to email you a copy, click here.*
*If you leave the page, the form might reset and the information you have entered could be lost.
I have my mininum system size.
Go to Step Four
Let us design your system

To get a ballpark idea of what your system might cost:

Click the button on the right to view our off-grid ballpark cost table.

Last updated: 09/20/2018

System size (kW) Daily Production Estimate Example panel configuration Approximate Price Range (before 30% federal tax credit)
1.1 kWSummer 4.5 kWh
Winter 2.0 kWh
4 × 275 W$7,100
1.65 kWSummer 11.0 kWh
Winter 5.5 kWh
6 × 275 W$9,800 - $14,800
3.3 kWSummer 14.5 kWh
Winter 7.0 kWh
12 × 275 W$12,300 - $22,600
4.13 kWSummer 18.5 kWh
Winter 9.0 kWh
15 × 275 W$13,200 - $23,500
4.95 kWSummer 22.0 kWh
Winter 11.0 kWh
18 × 275 W$15,500 - $25,800
6.6 kWSummer 29.5 kWh
Winter 14.5 kWh
24 × 275 W$23,800 - $44,600
7.08 kWSummer 31.5 kWh
Winter 15.5 kWh
24 × 295 W$25,700 - $46,500
8.25 kWSummer 37.0 kWh
Winter 18.5 kWh
30 × 275 W$25,600 - $46,400
8.85 kWSummer 39.5 kWh
Winter 19.5 kWh
30 × 295 W$28,000 - $48,800
9.9 kWSummer 44.5 kWh
Winter 22.0 kWh
36 × 275 W$32,200 - $54,700
12.38 kWSummer 55.5 kWh
Winter 27.5 kWh
45 × 275 W$41,300 - $44,400
13.28 kWSummer 59.5 kWh
Winter 29.5 kWh
45 × 295 W$44,900 - $48,000
14.85 kWSummer 66.5 kWh
Winter 33.0 kWh
54 × 275 W$44,100 - $47,200
14.85 kWSummer 74.0 kWh
Winter 37.0 kWh
54 × 275 W$61,500
17.7 kWSummer 79.5 kWh
Winter 39.5 kWh
60 × 295 W$68,100
19.8 kWSummer 89.0 kWh
Winter 44.5 kWh
72 × 275 W$67,900
21.24 kWSummer 95.5 kWh
Winter 47.5 kWh
72 × 295 W$73,600

These figures are based on complete solar power systems that Wholesale Solar sells. Prices are approximate. Prices do not include freight, tax, or installation.

Why are smaller systems sometimes more expensive than larger ones? Because higher-efficiency panels cost more. For example, to get a 10 kW system, you can either use 35 285W panels or 39 260W panels. Even though you need more 260W panels (they are less efficient), economies of scale actually make them more affordable. So when would you want to use higher-efficieny panels? Only when you're limited on roof/ground space and need to squeeze the most power out of every available square foot. In other words, more efficient panels cost more but can generate more power per square area. If you're not limited by space, we suggest you go with the best price per watt instead.

Click the button on the right to check out our pre-designed systems that closely match your current calculated off-grid needs. *

* Pricing on these systems does NOT include batteries.

Take your calculated numbers and explore the Off-Grid Systems.
Or give us a call at 1-800-472-1142. We are here to help!

Solar questions? Website problems? Please contact us.