In cold climates Synchro efficiency remains constant

Always

Electric Resistance Water Heater Vs Synchro 

Comparison Chart 

The water heater has an electrical resistance which, when new, is efficient at 0.8-0.9. After 2 years it collapses to 0.65. Synchro has a COP of 1.3 (even when it's -20°C outside).

The black curve features the performance of the most sophisticated water heater on the market. The blue curve shows the performance of a normal medium value water heater. In 2-3 years the electrical resistance inside the water heater becomes encrusted and loses all effectiveness

The Water Heater IS NOT EFFICIENT

Synchro YES, its efficiency remains constant, ALWAYS