Calculate each heater
A common portable heater is rated at 1,500 watts. At full output for eight hours, one heater uses 12 kWh. Two use 24 kWh. Multiply that by your electric rate and the number of heating days.
Compare the job, not just the equipment
A small heater warms a limited area. A central system serves much more of the home. Spot heating may save money if it lets you lower the whole-house setting and heat only one occupied room. It is not an equal comparison if the rest of the house must remain at the same temperature.
Heat pumps change the math
Electric resistance heaters create roughly one unit of heat for one unit of electricity at the point of use. A functioning heat pump moves heat and can deliver more heat per unit of electricity under suitable conditions. Extremely cold weather, defrost, or auxiliary heat can change its performance.
Electrical safety is part of the decision
A 1,500-watt heater is a substantial continuous load on a typical household circuit. Follow the manufacturer’s instructions, maintain clearances, connect directly as directed, and stop using equipment with hot plugs, damaged cords, or loose receptacles.