> If it was only effective with intermittent use then we wouldn't insulate water heaters as they're 24/7.
Water heaters are not running 24/7.
The entire point of water heater insulation is that you run them to heat up the water in the tank, then the water sits there at temperature, and when needed it has a fast response time (and also actually provides hot water as the heating loops generally don't have the heating capacity to bring the water up from ambient or sometimes just above freezing to sanitary at the flow rates users ask for).
