Electric shower head

Constant hot water, constant savings

I lived in Costa Rica for a year, and while travelling there I discovered the electric shower head, a great way to save energy on hot water. If you live in North America you have probably not heard of these marvelous inventions, unless you live in a mobile home, or are at the cutting edge of energy efficiency. What are they?

An electric shower head heats ambient-temperature water to a comfortable shower temperature as it is coming out the shower head. This means you don’t need to keep a tank of water hot just so you can take a shower. Or, if you live in a cooler climate, you don’t have to keep your water as hot for other uses.

A comfortable shower temperature is usually slightly warmer than body temperature – about 38 to 42C, or 100 to 108F. If you’re a devoted energy conserver, there aren’t a lot of other household hot water uses that require that hot a temperature.

In fact you can do pretty much everything else in cold water, including laundry, dishes, filling the mop bucket, even running your automatic dishwasher (which, if ENERGY STAR rated, has its own built-in heater, although not all of them can handle starting from cold water). The only exception would be a bath, but if you can live without the occasional hot bath, you can cut your hot water bill to almost zero with an electric shower water heater.

Can you really survive with no other hot water?

My initial reaction to this shower head (which I tried in Costa Rica in about ten different versions as I hopped from house to hotel to house) was that it would never work in a cold country like Canada. Why? Because the water coming out my tap in Toronto is about 4C or 39F for much of the year, and even washing your hands in water that cold is extremely uncomfortable. If you have to heat water for washing your hands, why bother with the extra hardware of an electric shower fitting?

In tropical countries like Costa Rica, this isn’t a problem. Since the weather is warm or hot year-round, the water coming out the cold water tap is typically between 18C and 24C, which is warm enough that you don’t get chilblains washing your hands in it. People in Costa Rica earn much less, on average, than North Americans, so they are more careful with their energy use. They wash their clothes and dishes in cold water too, and in fact in most houses the plumbing doesn’t even have a hot water pipe. A shower is the only thing they can’t handle taking cold. But that doesn’t seem to make sense for North Americans, at least not in cooler areas.

Then it occurred to me that the main reason North Americans set our hot water heater temperature so high (especially for tank water heaters) is so that we can take a nice long shower and not run out of hot water. If we could get by with warm water out of the hot water tank – for washing hands, doing dishes, running the dishwasher, filling the mop bucket – and with cold water for everything else, showers would be the only reason we would need our tank heater set to 60C or 140F. But if we used an electric shower head, we could have endless hot water in our showers (not that most serious energy savers would ever have a shower more than about ten or fifteen minutes long), and set our hot water tank heater as low as 38C or 100F. That would still give us water warm enough to wash our hands or dishes in, and might put a big dent in our hot water bill.

Note that the Canadian Government, for one, warns of the risk of Legionella or other bacterial diseases building up in hot water tanks that are not kept hot enough. I’m not sure what the bacteria would be breeding on if your water is clean, or how they would breed if you have chlorine in your water supply. But be forewarned.

Heating cold water to a comfortable temperature

Legionella warnings aside, as far as the input temperature being too cold, the fact is that you can still get hot water out with cold water going in – you just have to reduce the flow. One brand of shower head, Coral by Lorenzetti, claims it can take incoming water as low as 40F or 4C (above 50F or 10C is recommended). So it will work, at least marginally, in Canada. You just might have to shower under a trickle of water.

When selecting an electric shower head for use in a cold climate, it is very important to consider the input water temperature and the wattage of the unit. Consider the Fame 5400 watt electric showerhead pictured here. 5,400 watts is enough energy to warm 1.8 gallons of water by 20 degrees Fahrenheit in a minute. 1.8 gallons per minute is the typical flow for a low-flow showerhead, which means that if your input water is a balmy 80F or 27C, as it typically is in Costa Rica (or in Brazil, where many electric shower heads are made), your hot shower will run at full blast at 100F or 38C, which, being just above body temperature, will at least be comfortable in a warm bathroom.

But what if you’re in chilly Toronto in the winter? The water in my tap comes out at around 39-43F. To heat that to a comfortable 100F is a differential of roughly 59F. With 5400 watts of input from the Fame showerhead, the water flow would have to throttle back to about 0.64 gallons per minute, which is about a cup of water every ten seconds, to get to a comfortable temperature. And unlike electric tankless water heaters, some of which can throttle back the flow to maintain the desired output temperature, most electric shower heads don’t have an automatic throttling feature so they just fail to warm the water sufficiently. (Some do have different selectable output levels, so you can at least choose between a freezing fast-flow shower and a lukewarm dribble). So in a cold climate the best use for these shower heads is probably for something like an outdoor pool shower or a summer cottage shower – or to heat the water to a comfort temperature from a hot water source, while keeping the hot water tank below comfortable shower temperature.

Does the idea of washing your hands, or doing dishes, in cold water sound intolerable? Maybe, but bear in mind that in many colder countries this is the norm. In Japan many houses have no hot water except for showering. And the winters can get pretty chilly there. This is just a discomfort people suffer because their energy is priced high enough to motivate them to make sacrifices.

Temperature and safety problems

There are two main problems with electric shower heads: temperature and safety.

Temperature control

As pointed out above, the temperature out of the shower head depends on the speed of water flow, the temperature of the incoming water, and the available current. So there is no way to consistently get the same temperature each time you shower, unless your water pressure and voltage are constant, and you can memorize exactly how much to open the shower spigot. It does take a bit of getting used to; I was warned that if I set the water too slow, I might get burned by the excessive heating of a small amount of water. But the shower heads seem to have a built-in sensor to prevent this – I haven’t been burned once. On the other hand, there have been times when the heat took a long time to kick in. Some of them appear to have a preheat period, and that period is sensitive to how fast the water flow is (but whether more flow means a faster preheat or not, I haven’t been able to determine consistently).

The point is, these electric shower heads take a little getting used to. But the more I use them the more convinced I am they make sense for any climate where a hot water heater isn’t needed for other uses.

Safety issues

Because electric shower heads are electrical devices they carry some risk of electric shock if installed incorrectly. Note these key points before purchasing and installing yours:

• Make sure the model you purchase is certified for use in your jurisdiction. In the US and Canada this means it must be certified by either Underwriters Laboratory (UL), or the Canadian Standards Association (CSA). Either certification is acceptable for either country, and both are recognized in a wide range of other countries. Don’t install something that isn’t certified – you’re increasing your risk of injury and you may be buying a poor-quality product.
• No wires should be exposed. Of the ones I’ve tried in Costa Rica, many have the electric wires for the shower head connected with just a joiner cap and some electrical tape. It would be easy for a tall person, while trying to reach up for a bottle of shampoo on a ledge, to accidentally touch the joiner cap, and if it wasn’t completely sealed, the water from their fingers might trigger an electric shock.
• The wiring must be properly grounded – really well grounded in fact. And if you live in a dry area this may be a challenge. Even a copper pipe going into the ground may not provide a proper grounding if the soil is dry – you may need to dump water or saltwater down where the grounding pipe is periodically.
• The circuit must be a dedicated circuit with the appropriate amperage. Most of these showers require a 30 or 40 amp circuit. (They are energy hogs for the few minutes they’re on – but they’re hardly ever on!) If you don’t have them on a high enough circuit you may keep blowing the circuit, which is not a fun thing to have happen when you’re covered in shampoo and soap and the water goes permanently cold. Not to mention a fire and electrical hazard.
• The weight of the shower head heater element, and the fact that the shower head often extends out some distance from the wall (because many of these electric shower heads project straight down, not at an angle), means the shower head may need to be supported by more than the pipe coming out of the wall. Laundry wire or cabling connecting the shower head-end of the water pipe to points above on the wall or ceiling is usually used. You don’t want a running shower head crashing down on you as you’re showering!

Energy savings with electric shower heads

Manufacturers of electric shower heads claim huge energy savings over using a conventional hot water tank. Be wary of these claims. Note the following:

• The claims typically refer to the energy efficiency only of the hot water used for the shower. If you need hot water for anything else, this efficiency claim won’t mean much for you – the other uses will still operate at the efficiency of your regular hot water heater.
• The claims typically refer to an improvement in energy efficiency versus an electric tank hot water heater. It’s not clear how efficient a tank hot water heater they are comparing to. There is a large variation in electric tank hot water heater efficiency, since for one thing the amount of insulation on a tank has a huge impact on its efficiency.
• If you are metered on time-of-use, or worse yet, on peak usage (peak usage is typically only for commercial customers though), these appliances can really be costly even if energy efficient. That’s because their heating elements are between 2.5 and 5 kilowatts (2,500 to 5,000 watts). So while they don’t use much energy over the course of a day, while they are operating they are using a lot. (An analogy would be a fire hose turned on for ten seconds – short but full of power!) As a result, anyone on time-of-use metering will pay more than expected for this hot water if they shower during peak times. For peak usage – where part of your bill is based on your peak consumption through the month – having this heater on and another high-wattage device such as central air at the same time, can really push your peak up, and hence the peak part of your bill.

Electric water heater faucets

Another related innovation is the kitchen water faucet with a built-in electric heater. This device is useful for situations where you don’t have another source of hot water and you’re willing to put up with a modest amount of heating – as in, cold water becomes lukewarm, or lukewarm becomes mildly hot. One use case is a trailer where you don’t want the expense of a built-in water heater (or where your only other use for heated water is a shower, and you opt for an electric shower head like one of the ones above. I’ve never used one but I think the idea of heating the water right at the point of use is a cool idea. At 2500 watts, this unit won’t produce a lot of heat, but certainly enough to wash the dishes. The manufacturer claims it can raise the temperature by 60 degrees Celsius, which in theory means it can get any water hot enough – but customer reviews suggest it’s not that strong. It also requires that you have a dedicated 20 or even 30 amp circuit (110 volts x 20 amps = 2200 watts – so a 20 amp circuit is not quite enough) to power the unit. An interesting idea at the least, but it definitely hasn’t gained the traction of electric shower heads.