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Q. Dear Umbra,
We are a family of five, with three little boys growing bigger every day. Which is the better environmental investment for our family: to replace our existing hot water heater with a solar model, or to switch to an on-demand, “instantaneous” hot water system?
Gillian and Grant
A. Dearest Gillian and Grant,
Solar hot water is the better choice and would still be so if your children grew not one inch taller. Solar hot water takes advantage of the sun hitting your roof, which hopefully happens regularly without costing you money, nor the Earth anguish. A tankless heater will still use a polluting energy source to heat the water. It is a rare ratepayer who gets electricity from all-renewable sources, and Torontoians (?) seem to have the usual mix of coal, gas, nukes, hydro, and so forth.
All a tankless model does differently from your (I assume conventional) hot water heater is heat water as you need it, rather than storing hot water for hours. Like your tank heater, it uses either an electric coil or a gas fire to do this. A tankless on-demand model is, in the best scenario, a bit more efficient than your existing hot water heater. But it still has all the problems of using a non-renewable resource: pollution, greenhouse gas production, a sufficient power generation and delivery system, and of course reliance on the supply of whatever resource is used. You might be interested in reading my earlier column on tankless heaters.
A solar hot water system, on the other hand, can provide the bulk of your hot water needs without using any non-renewable resources (other than those used to make the equipment). Solar hot water is neither a new nor a highly complex technology, so you need not be a brave early adopter to have a system installed. There are a wide variety of systems (again, see a previous Umbra solar water love-fest) to choose from, and there are often financial incentives from one’s city or state. Toronto seems to have a solar hot water initiative heating up right now, in fact, and here is a list of system suppliers to peruse.
The two potential drawbacks that I see are the initial financial outlay and whether your roof and home are well situated. But you won’t know whether these are actual or theoretical drawbacks for your specific situation until you investigate the systems available where you live, their costs, and the fabulous financial incentives that might be coming your way. Here are some resources from the U.S. government on solar water heaters and how to calculate their costs.
Always choose the sun over the coal mine.