Average Solar Production in Montana USA

Introduction – Data Source and Assumptions

Data is from the NREL.gov app for average solar radiation energy per day in Billings, Montana. We used this reference point to compute the solar radiation energy production per day (in kWh/m²), which changes throughout the year according to the month. Each month is different due to the changing relative trajectory of the sun.

To get the monthly production, we simply multiplied by the number of days for each month. Finally to get the annual production, we added up all of the monthly values.

The average solar panel surface area is estimated to be 1.5 square meters. The efficiency of converting solar radiation into energy is estimated to be 15%.

Average Electricity Usage in Montana and How Many Solar Panels You Need

The average monthly electricity usage in Montana is 29 kWh per day, 858 kWh per month or 10296 kWh per year. Based on the data below, you would need 17-58 panels depending on the time of year to cover your electricity costs exactly. The variable factors are that electricity usage varies depending on how hot are summers and how cold are winters, and whether you use electricity based cooling and heating. Check with your solar system installer for exact numbers.

MonthSolar radiation per daySolar radiation per monthSolar energy per month 1 panelSolar energy per month 20 panels 
January2.26 kWh/m²70.06 kWh/m²15.76 kWh315.27 kWh
February3.35 kWh/m²93.80 kWh/m²21.11 kWh422.10 kWh
March4.55 kWh/m²141.05 kWh/m²31.74 kWh634.73 kWh
April5.45 kWh/m²163.50 kWh/m²36.79 kWh735.75 kWh
May6.26 kWh/m²194.06 kWh/m²43.66 kWh873.27 kWh
June6.82 kWh/m²204.60 kWh/m²46.04 kWh920.70 kWh
July7.48 kWh/m²231.88 kWh/m²52.17 kWh1043.46 kWh
August6.72 kWh/m²208.32 kWh/m²46.87 kWh937.44 kWh
September5.47 kWh/m²164.10 kWh/m²36.92 kWh738.45 kWh
October3.58 kWh/m²110.98 kWh/m²24.97 kWh499.41 kWh
November2.67 kWh/m²80.10 kWh/m²18.02 kWh360.45 kWh
December2.11 kWh/m²65.41 kWh/m²14.72 kWh294.35 kWh
Anne Lauer
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Anna Lauer is a writer, gardener, and homesteader living in rural Wisconsin. She has written for Mother Earth News, Grit, and Hobby Farms magazines. Anna is writing a new book about growing your food for free and an ultimate guide to producing food at little to no cost. When shes not writing or gardening, Anna enjoys spending time with her husband and two young daughters.

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