Each unit is outfitted with a 40 kW magnetic, self-powered generator providing free electricity, along with a 10,000‑gallon water storage tank and an air‑to‑water system that produces between 240 and 500 gallons daily. Construction costs typically range from $40,000 to $48,000. You may choose an underground backyard placement that supports a year‑round growing season. An underground constructed home maintains an average temperature of about 52°F year‑round, so you generally only require supplemental heating and fans for air circulation.