Hot Water

22% of domestic energy consumption

 Water heating is a large part of the home energy budget.

 Use Less Water – Equipment

 The first area to focus on water use. If you use less water, this will automatically reduce hot water use, and cost. The simplest and cheapest actions are to install flow restrictors on most of the water taps in the house. All hand wash basins should have them. However, there is little point fitting a flow restrictor to the kitchen sink. Here, one usually wants to fill the sink rapidly, and little will be saved by slowing flow.

 Shower heads should be replaced with flow restricting units. There are a large number available in hardware stores. The best ones are small – the size of a toddler’s fist and made of chrome-plated brass, but not widely available. Some plastic ones are also good. Unless you have a water softener or live in a soft water area, stay away from complicated adjustable units promising pulsating massages. These will not work well after a several months of hard water has passed through. They can be restored by soaking in hot vinegar. The simple units usually clean up well, to like-new performance.

 The final way to reduce water consumption is to replace conventional toilets (16-21 litre flush) with low volume flush units (6 litre flush). Although this will have little direct effect on your water heating bills, there will be an effect on winter energy efficiency. The water in your toilet’s tank gradually warms to room temperature as it sits. The less water you flush, the less fresh water is being heated in your tank between flushes.

 Use Less Water – Behaviour Modification

 How you wash your hands, face, dishes, and teeth can make a huge difference to water (hot & cold) consumption. There is no need to wash your hands under a fast flowing tap. Hand-washing of dishes is more effective in a sink filled with water and detergent than under running water. Five minutes of soapy water soaking makes grease and soil easier to remove. Afterwards, rinse in a sink part filled with clean water. Wash the relatively clean stuff first, leaving greasy pans for last.

 How much difference can this make? My family of four, including 2 teenaged daughters with long hair, took in a nephew from Quebec who wished to learn English. He stayed with us for a year. Two months after he had arrived, I noticed that our water consumption had doubled. I spoke to him about the way he washed dishes and his 20-minute showers, pointing out that he alone had doubled our water use! I made it quite clear that money was not the issue – the cost was small. Once my nephew understood that energy and water efficiency was my “religion”, he changed his behaviour, and our water use dropped dramatically to the expected 15% – 20% above its previous low level!

 Energy Source

 There are basically just two ways to heat water in Canada: electricity and gas. Electrically heated water tanks are more common; installation costs far less than gas. However, gas should heat water for about 1/3 the cost of electricity. Gas water heaters also “recover” rapidly after being drained.

 Both types should be well insulated to retain heat during the periods between use. Most gas water heaters and newer electric heaters are well insulated. For those that are not, hot water tank “blankets” are cheap and easy to install. They will save many times their cost every year!

 An alternative to a hot water storage tank is a “demand” heater. These are compact, high output gas or electric water heaters which warm flowing water as the householder calls for it. There is no storage tank to lose heat. These are worth considering if hot water use is intermittent with long periods of no demand. Some gas-fired models claim to be more efficient than conventional heaters.

 Some hot water taps are far from the hot water tank. Many litres of cold water must be flushed from the plumbing before any hot water appears. These may be candidates for a small, below-counter, demand heater. In these cases, an electric unit may be more economical than a gas-fired one – unless a lot of hot water is consumed at that tap. Then hot water demand is anyway best satisfied from the central supply.


 In our land of cheap energy and cold winters, solar hot water heaters are seldom considered. However, in sunny lands like Greece, Israel, Italy, and (oddly) Zimbabwe, solar water heaters are very popular. Of course, making a solar hot water “collector” work in Canada is more challenging because it must cope with freezing winter cold.

 A solar “collector” is a low frame insulated below and glazed with a single layer of glass above. Under the glass are black coloured pipes through which water is pumped. The box is tilted towards the south to more efficiently catch the sun. Generally the degree of tilt is governed by the slope of the roof, where the collector is usually mounted. The water pumped through the solar collector must contain antifreeze to resist freezing on winter nights.

 A solar hot water heater in Canada cannot replace your gas or electric unit. It supplements it. In winter it can reduce your domestic hot water costs by 20% – 30%, depending on location and number of sunny days. In the middle of summer, the unit should supply almost all of your hot water, depending on how you time your use of hot water. If you do dishes and laundry at night, there may be no sun-warmed water left for early morning showers.

 A solar hot water heater – typical cost is $3000 – may make sense if you heat water electrically. On the other hand, if you have one, you will be partly protected against electricity or gas price rises. Estimate how much hot water costs you and assume that this will be halved by installing a solar unit.

Hot Water