The best replacement for heaters is tank water heaters.

The best alternatives to heaters are rated as following:
★★★★★  tank water heaters
★★★★★  electric heaters
★★★★  central heating
★★★★  gas
★★★★  central heat
★★★★  electric water heaters
★★★  gas water heaters
★★★  furnace
★★★  electric
★★  radiator
★★  ceramic heaters
★★  tankless
★★  electric baseboard
★★  propane
★★  oil filled radiators
★★  gas heat
★★  electric radiators
★  electric fireplaces
★  infrared heaters
★  ceramic
★  space heaters
★  tank
★  forced air
★  fan
★  quartz heaters
★  baseboard
★  radiators
★  electric space heaters
★  stoves
★  oil filled
★  electric hot water heaters
★  oil filled heaters
★  gas furnace
★  propane heaters
★  gas heaters
★  fan heaters
  tanks
  tankless water heaters
  gas pool heaters
  regular water heaters
  convector heaters
  ventless gas logs
  water heaters
  gas tankless water heaters
  conventional water heaters
  gas pool heater
  blue flame
  heat pumps
  tank hot water heaters
  edenpure

Your alternative for heaters is not listed? Suggest!
Speaking about heaters, one probably shouldn't forget about fans.

Other search terms related to heaters and their ratings are:
★★★★★ fans
★★ blowers
★★ tanks
★ economy 7
You have in mind a companion for heaters and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of heaters in all years. Click on graph for more.
heaters
tank water heaters
electric heaters