Enter your greenhouse size, heater wattage, and expected nightly runtime to estimate seasonal electric heating cost.
A well-sealed greenhouse with thermal mass (water barrels, stone) or a double-poly covering can cut heater runtime substantially compared to a thin single-layer structure with air leaks.
A greenhouse's heat loss depends heavily on covering type, air sealing, and thermal mass — a double-layer poly covering with an air gap insulates dramatically better than a single layer, directly cutting the hours a heater needs to run each cold night. Passive solar strategies like water barrels that absorb daytime heat and release it overnight can reduce electric heating need further, similar in spirit to how passive attic ventilation reduces a home's cooling load.
Yes, often meaningfully — water barrels or stone that absorb heat during the day and release it slowly overnight can reduce the temperature drop a heater needs to compensate for, directly cutting runtime.
It depends on your climate and electricity rate — some growers use propane or passive solar design instead, but electric heaters remain popular for their simplicity and precise thermostat control.