Tankless Water Heater

When we bought the house in 2005 it had a “relatively new” gas hot water tank.  Relative compared to an 80 year old house and 40 year old furnace.  The tank indicated that it had a 10 year warranty so we figured we were safe “for a few years”.  15 years later when we were out of town, a friend who was living with us at the time texted to say that the water coming out of the hot water tap was rusty.  He sent a picture.  He was right.

He turned off the water supply to the hot water tank and left to go to his girlfriends.

I have always objected to wasting energy keeping 40 gallons of water hot all day when it is used in the morning for showers and in the evening for doing dishes.  In Europe almost every place we have stayed had tankless on demand water heaters.  If you have never heard of them, they are units where water flows through a heater.  They turn on when the water starts flowing and bring it up to a set temperature.  You turn off the hot water and the heater turns off.

You can get electric and gas tankless heaters. They work on the same principal with electric having the advantage of no CO2 emissions.  A friend who works in carbon negative building swears by the electric ones.  We ended up going with a gas unit from Rinnai for a number of reasons.

1. Plumbers are not electricians.  Yeah, seems obvious but all of the suppliers we could find locally were plumbers and quoted on gas units.  I think this is because most are certified on gas as well so they could look after the entire installation themselves.  An electric tankless heater would require them to line up an electrician for the power adding to the complexity and cost.
2. Limits on electrical power.  If we had been able to wait until the renovation we might have gone electric as we would have had an electrician here anyway and we will likely upgrade the electrical service so that we can be ready to install a car charger.  As it was we are not certain about whether the house has adequate power supply.  
3. Existing gas service.  If you are doing a new build passive house in a rural area with no gas service, then an electric tankless heater is pretty much your only option unless you want to have gas deliveries and keep a tank in your yard.  We had the gas in the house already which was close to the unit so it was easy.
4. Time.  When we came back we had started using the tank again and the water was running clearer (rust on the bottom was likely disturbed by a sacrificial rod rusting through and falling to the bottom)  but we didn’t want to drag out the decision process any longer than we had to.  We spent an anxious month checking the tank for leaks daily.  

The heater has been in now for over 6 months and so far we love it and have had no problems. Lots of hot water for multiple morning showers and dishwashers and our gas usage dropped by about ⅓ in the summer months when all gas used is for water heating.  I don’t think either our furnace or water heater have pilot lights. You do have to wait a bit longer for the hot water to arrive which requires some changes of habit, for example, don’t just turn on the hot water tap to rinse a dish.  You can get a recirculating system that keeps warm water in the pipes but that seemed unnecessary and sort of defeats the purpose of a tankless system to reduce heating water you are not using.

What would we do differently? 

Ideally we would have replaced it as part of the reno and get a unit that does in floor heating as well as on demand hot water.  That would have been my preference and perhaps we should have purchased a unit that could handle that but there was a lot going on at the time and we weren’t sure when or if Sarah would get called back to her job (pandemic).  The dual purpose units are considerably more expensive and some reviews indicated that by trying to do both things, they don’t do a good job of either.  We could have just replaced the old tank with a used tank to hold us over until the reno but that would needlessly create waste and left our chimney in use eliminating the option of taking out the chimney ourselves. 

I probably shouldn’t have told the installers that we were going to replace the foundation because they did a really crappy job that i would have complained about had i been planning on keeping it.  They mis-measured the outside vent so had to put two holes in our exterior wall which i was less than thrilled about, but since that is going to be replaced I didn’t make a big deal about it. They also left the gas and water supply pipes dangling out in the open.  Pretty disappointing really but i will assume that they felt they had permission because it was a temporary installation.

It never occurred to me at the time but we also could also have picked up an electric unit from Home Depot or Lowes or even direct from the manufacturer and i could have tackled the plumbing myself and just hired an electrician to hook it up. That would have eliminated the need for the exterior venting and saved the hole in the wall. It would also have reduced our carbon footprint even more. My concern with that would be the power supply and heating ability. The largest electric listed at Home Depot says it can handle 2 showers and if you need more, go gas. The unit also needs 2 double pole 40 amp breakers so if we could get a larger unit, it would need even more power which i don’t think we have room for right now. With plans for a suite we could need to handle 2 showers and a dishwasher or other use so i think we made the right choice.

Cost

Tankless are a lot more expensive than just replacing a tank.  We got 2 quotes  Both showed up to look at what was required and gave me advice on the space they needed.  Company 1 quoted without the gas permit fee but indicated what the permit would cost.  Company 2 included the gas permit but did some “salesmanship” that seemed a little deceptive.  Their quote was much higher but provided a promotional discount if we “act quickly” because they have a gap between jobs and want to keep the crew busy.  The discount brought their price down to be the same as the first company’s quote if we included the gas permit.  That struck me as deceptive so we went with company 1.  The gas permit is required to get the $1000 rebate from Fortis, our local gas company, and came in higher than either company had quoted.  Not sure what happened there but since they both got it wrong i will assume it is legit.  Also, despite telling our plumber that we were applying for the grant and would need the permit, they did not get us one until AFTER the installation when we called to get the permit number. Perhaps this is why it cost extra. With permit and taxes it came in around $5000 (CAD of course) before our $1000 rebate.