Build a month by month energy profile
Loads change with the seasons: more lighting and heating fans in winter, more cooling and pumping in summer. You need loads by month so you can compare them with the sun available in each month.
How
- Copy the load table into 12 monthly columns and adjust hours for each season (lighting hours, irrigation pumping, cooling fans, heat tape or circulation pumps).
- Calculate daily kWh for each month.
- Split loads into critical (water pump, fridge, communications, medical devices) and non-critical. Critical loads set your autonomy needs in step power-12.
- Keep this table: you will divide it by monthly sun figures in step power-4 to find the critical design month.
Sources
- Planning a Home Renewable Energy System. US Department of Energy, Energy Saver, accessed 2026-11
- Stand-alone system sizing (AE 868 Commercial Solar Electric Systems). Penn State University, John A. Dutton e-Education Institute, accessed 2026-11