All of us use a lot of power and spend a lot of money to heat and store hot water. As promised so long ago we have sub-metered our 50 gallon tank style hot water heater to see just how much power it uses. Frankly – it uses an obscene percentage of our total electricity usage.
Over the period, May through August, as promised, we tracked the hot water electricity usage using a Hobo meter (cool little toy, kudos to my friend Rick for helping to figure out the best set-up). During that period, monthly hot water electricity usage was 262 kWh. In that same period, average total electricity usage averaged 377 kWh. That means that 70.3% of the total electricity usage was used to make sure that hot water was available on demand!!!!
Annualized that means that the hot water heater uses 3,142 kWh and costs $440 to run! Note that the federal government estimates that an average American household uses 3,162 kWh to heat hot water and that this costs $437.82 per year. So we are right in there with average usage.
Problem? With what should our aging heater be replaced? The hot water heater is old enough that I often wonder when we will come home to a basement full of water from a split tank. (Been there and done that.) This seems like such an easy question at the offset – set criteria, research the most efficient options, install best option, save money. Turns out it isn’t that simple.
First things first, establish some criteria for selection:
- Rely on site generated power – so no gas
- Save money on operation by increasing efficiency, Energy Star rated preferred
- Simple to operate and maintain system – no change in lifestyle
- Be budget aware
- Quick payback on investment
- Try to be future flexible and design with the idea of installing a solar thermal system for heat and hot water.
The ‘no gas’ criteria #1 narrows the choices to tank based electric and solar thermal water heaters.
Electric hot water tank heaters are really no more efficient today than they were 15 years ago. The fact that they offer very little energy savings means that they do not meet Energy Star requirements.
Solar thermal with and without backup are hard on the upfront budget so criteria four is a challenge. The payback for a no-backup system is within the range of attractive but no-backup seems risky. Also, solar thermal brings with it a level of complication on the maintenance side including snow removal and storage tank inspections. Although minimal, this means a little bit more complication in the operations of the house. That means criteria three is not met either.
What remains? A heat pump hot water heater:
- Operations are expected to not exceed current on-site PV power generation
- Medium up front investment for significant operating savings and Energy Star rating
- Although the technology is different than a traditional electric tank heater, the maintenance and operations are simple
- And the tank could be made to serve as a backup to a solar hot water system
Current hot water heating costs are $440 per year. Installing the heat pump hot water heater is estimated to save $169 a year – a significant savings! Next up – installation, monitoring and reporting on the heat pump hot water heater!
