Quick Answer
Instant electric water heaters are generally more expensive upfront but offer long-term energy and cost savings compared to traditional tank electric water heaters, which continue to use energy even when not in use.
Upfront Costs
The upfront cost of instant electric water heaters is higher, typically ranging from $800 to $2,000 for a single unit, depending on the brand, model, and features. In contrast, tank electric water heaters can cost anywhere from $400 to $1,500 for a basic model. However, when considering the cost of a tank, such as a 50-gallon unit, you must also factor in the cost of the tank itself, which can range from $300 to $1,000. This brings the total cost of a tank electric water heater to around $700 to $2,500.
Energy Efficiency
Instant electric water heaters use a significantly lower amount of energy than tank electric water heaters. According to the U.S. Department of Energy, a tankless water heater can save up to 34% of energy compared to a traditional tank water heater. This is because instant water heaters only heat water when needed, whereas tank water heaters continuously heat and reheat the water in the tank. With an instant water heater, you can expect to pay around $30 to $60 per year in electric bills, whereas a tank water heater can cost upwards of $150 to $300 per year.
System Design Considerations
When designing an off-grid solar system, it’s essential to consider the flow rate and temperature requirements of the instant water heater. A general rule of thumb is to size the solar array to produce 30% to 50% more power than the water heater’s maximum power consumption. This ensures that you have a buffer for cloudy days or increased water demand. Additionally, you may want to consider installing a high-efficiency pump to reduce energy consumption and minimize the strain on the solar array.
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