1. Mayhew C. and Simmon R., (NASA/GSFC), NOAA/NGDC,DMSP Digital Archive, Astronomy Picture of the Day (Earth at Night) (Image) 2000. Retrieved from https://apod.nasa.gov/apod/ap001127.html.
2. Household composition statistics (2017). Retrieved from https://ec.europa.eu/eurostat/statistics-explained/index.php/Householdcompositionstatistics# Household size.
3. Morris C., German power bil ls are low compared to US average (Blog) 2015. Retrieved from https://energytransition.org/2015/05/german-power-bills-low-compared-to-us/.
4. Morris C., High German power prices, low monthly bil ls? (Blog) 2018. Retrieved from https://energytransition.org/2018/02/high-german-power-prices-low-monthly-bills/.
5. Thalman E. and Wehrmann B., What German households pay for power, Clean Energy Wire 2019. Retrieved from https://www.cleanenergywire.org/factsheets/what-german-households-pay-power.