On demand electric heaters will save you money at first but are more harmful to the environment, and are not as good for the efforts of the utilities managing the electrical grid. That is why these heaters are falling out of favor in countries such as Japan where until recently they were very popular.
The main reason tankless heaters save money is that in a tank water heater, you produce heat throughout the day for use later, and some of that heat escapes from the tank into the surrounding living space (or furnace room or wherever your hot water heater is located).
You can compensate for this heat loss to some extent by properly insulating your hot water tank (special insulating blankets can be bought to this end - get the thickest one available), putting pipe insulation on your hot water plumbing, and by turning down the heater thermostat from the factory default of 140F to 120F, which is both more efficient and safer. But even with these changes you will probably discover that an on-demand heater costs less to operate, at least in the short term, because there is so little energy lost to heat escaping from the device, since there's no tank for the heat to escape from.
The reason I say electric tankless water heaters are not as good for the environment is that they create unpredictable spikes in electrical demand, which makes it more challenging for electrical utilities to manage generation load. An on demand electric heater draws a huge current while it is in use. A tank heater, however, draws a lesser current for a longer period, and stores that energy as heat. Imagine if in a city of a million, every home had an on demand electric heater, and everyone showered when they got up. The electricity company would need to rapidly increase electrical production in time for the tankless electric water heaters to heat water for showers, then to rapidly ramp down electricity production once the showering time (say, 8:30 in the morning) is more or less done. Since they can't ramp up this fast with fuels such as coal or nuclear, they wind up ramping up much earlier (say, 3 am), and then have to ramp down much later (say, 10 in the morning), so that while you have saved energy, you have indirectly required the electricity supplier to generate a significant amount of energy that isn't actually required, and may go to waste.
For this reason, in Japan for example, there is a major campaign underway to convince homeowners to switch away from on demand electric heaters, and instead use a tank electric heater with some intelligence designed into it so that the tank heats water hotter when there is excess power available, and then blends that water with colder water if necessary, to supply hot water at a steady temperature.
Then there's the issue of time-of-use pricing. In some states and provinces you are charged for electricity based on the time of day it is consumed, and in some areas you may even pay based on the peak amount you use. So if you shower at 8:30 in the morning you are showering during 'prime time' for electricity prices, and that means an on demand electric heater will cost you a lot of the expensive power, whereas a tank water heater, if it has the smarts built into it to predict that no hot water is typically required while you're off at work, can give you hot water stored up overnight, then not draw more electricity to heat the tank until the next evening, when electricity prices have dropped.
The other point to think about is the lifestyle changes you will need to make when you switch to an electric tankless water heater. The house I live in now has an electric tankless water heater, and I must say it does not work as well as I would like. The flow is much slower than you might get from a tank heater (because the tankless heater only lets through as much hot water as it can produce at that time), and for a job like cleaning pots and pans, where you might turn the tap on, then switch it off, then back on, then off again, it just doesn't work like a tank heater does, because there is a lag between when the water starts running and when the tankless heater engages. So your pipe is like a sediment core of cold and hot sections moving towards the tap.
All in all, while on demand electric heaters are getting a lot of attention at present, and may become more common in the US over the next two or three years, I predict that their popularity will not last, because of all the drawbacks mentioned above, both to homeowners and utilities struggling to manage peak electricity load. If you're considering purchasing an on demand electric heater, expect to see short-term savings replaced with higher electricity bills over time, as electricity companies put more pressure on consumers to cut their peak demand, and don't be surprised if the performance of your heater doesn't meet your expectations, in terms of constant heat output or the heater's ability to handle intermittent hot water needs.
No comments:
Post a Comment