Why we converted our Natural Gas water heater to a tankless Electric on-demand
Posted on: March 6, 2018, by : geek1

Why should we put in more efficient appliances?

There’s a lot of talk about reducing fossil fuel use, lowering our carbon footprint, and being more efficient by using common sense and renewable energies. Canada is a fossil fuel rich country, and one of the largest exporters of fossil fuels, the last I checked, we were at #5 in the world, here’s a more indepth read of the details if you are into that stuff. If you have school aged children, you are likely to have heard them talk about climate science and hopefully that have taken home some facts and practical solutions for you and your family to use today, to help us all for future generations. You have also likely read a lot of media on the subject, and we are obviously being told that we must reduce our ecological footprint. I thinks its a good idea to first have some idea of what our lifestyle does to the planet, or as a 1st world civilization, how much we consume of our natural resources. A great place to start is with the global footprint calculator created by the Global Footprint Network. This simple tool provides you with a quick view of your families impact on the environment and approximately how many planet Earth’s you need to sustain your lifestyle. What’s super interesting is when you make some simple changes in your lifestyle, you can really cut down.  So enough about the main reason to switch off of Natural Gas, let’s get into more detail.

What options are there for my old ng water heater?

Our very old, 30+ years, 40 gal/180l natural gas water heater finally gave up, by evidence of water leakage. This water heater was not efficient, used a simple gas fired boiler system with a constant pilot light, it would be rated on the lower end of the efficiency scale at maybe 65%. This is nowhere near any Energy Star rated appliance they make these days. Now here in BC, natural gas is pretty cheap and it heats really well for the $, but as a limited resource and a releaser of carbon into our atmosphere, its not something that should be used if possible. We want to capture carbon and keep it in the ground.

So an obvious choice is to put in a much higher efficiency ng water heater.

  • The most efficient ng water heaters are called high efficiency condensing hot water heaters, these recycle the waste gases and make these appliances as much as 98% efficient, that’s pretty damn good, and you really can’t ask for much better.
  • They do have moving parts, fans and smaller 1 1/2 – 2 inch inlet and exhaust pipes made from PVC pipes sticking out of the sides of homes. You have likely seen a home with steam coming out the side from a small white pipe, this is mostly the steam from the ng condensing water heater or furnace.
  • These highly efficient wh’s have a cost that’s appropriate for the technology, and as they are more complex, they can wear out before their typical 5 year limited warranties, where parts are usually covered, by labour isn’t. A quality unit is likely to cost you around $3,000. Installation another $1000 if this is your first high efficiency ng heating system.
  • As a water heater with a tank reservoir of a fixed size, your consumption at any given time is limited to its capacity, so a 200 litre tank is a good size for a family of 2-4 depending on your hot water usage.
  • Physical size of a water heater can be significant, take the size of the unit itself, then the service clearances required for possible repairs or adjustments, then add the inlet and exhaust piping required.
  • Having a tank with preheated hot water does make it’s availability quite instant, depending on how far the tank is from the needed source. Hot water will be ready as soon as it reaches the tap, in our home, the ground floor bathroom is only 15 feet of plumbing away from the heat source, so that takes 3-5 seconds.
  • Hot Water tanks eventually run out of the heated water, and you’ll start to feel this as a gradual change from the warmth you felt earlier.
  • Installation generally requires a Plumber/Gas fitter and Electrician, but most plumbing companies do all these trades.

Another option is an electric hot water tank.

Electric water heater
Basic Electric tank hot water heater

Switching from Natural gas to electric heat will require some changes, and your home will need to have the overall capacity to support this additional electrical load. Older homes used to have a 60 amp service to the home, most of these would have been upgraded to at least 100 amp for insurance purposes, and the average new home has a 200 amp service. If you are on the lower end of the scale, you’re going to need to have it checked. BCHydro deployed smart meters to much of BC, so if you have a smart meter, you can see your actual consumption online, check out this link on Understanding your electricity use at BC Hydro, you’ll need to have a free login to see your specific details. In addition to your basic daily consumption, you can opt in and purchase a power monitor that reads your smart meter directly. I’ll discuss that in another post.

  • Electric hot water tanks are also quite efficient, most rated at ~93-96%, simply due to the fact that they have no moving parts and limited powered technology, and when well insulated, limited heat loss when not being used.
  • You eliminate the need for a natural gas supply or exhaust chimney for burning of the fuel. So this cuts down on the physical footprint and airflow considerations.
  • You will need to add a new electrical circuit from 20-40 amps at 230 volts ac and the associated electrical wire to the water heater from your electrical panel, similar to the size needed for an electric stove.
  • The cost of these units is much less than $1000, and installations should less than $500 depending on the Electrical wire effort.
  • A Plumber and Electrician would be needed for a new Electric water heater, or in general just a plumber if its a swap, as most plumbers hold a license that allows them to switch the wires from one water heater to another. but always ask who else is required for installation from your main contact.

On Demand or Tankless water heaters

The On Demand technology, or tankless as it may also be called are sometimes used interchangeably, but you do need to read the details carefully. The Typical On-Demand unit simply heats water only when you ask for it, meaning the water stays cold in the system and therefore uses no energy to maintain a set temperature.  These On-Demand units also require a minimum flow to activate the heating of the water, this can be a blessing and a curse if not considered. There are Electric On-Demand and Gas On-Demand, much like the tanked versions, they have similar attributes to Electric vs Natural Gas tanked models. Some On-Demand units incorporate a small tank reservoir and maintain that tank’s temperature at the set point you choose, which makes them more like a tanked system, but as the tanks are very small, as little as 1 litre to 10 litres, there physical size is much smaller. The smaller tanked versions really fit into the above 2 hot water tank categories and allow for smaller needs like a cottage of small shop shed. The true Tankless On-Demand units are available in many sizes from a small 250watt bathroom sink heater to extremely large commercial and institutional units in both electric and gas models. Due to the additional needs of Gas fired units, they don’t tend to be available in the smallest size ranges as the electric versions can be as small as a soda can. There are also some units that claim to be tankless but hold the internal components and water at the set temperature, this allows the units to provide more instant hot water at a cost to your energy use.

On-demand tankless electric water heater
  • True On-Demand units only heat water when you ask for it, doesn’t heat the water in the unit unless it detects flow, and if the flow isn’t enough, it stays off.
  • The On-Demand style also uses a much smaller physical footprint, usually being installed on a wall, and servicing is simpler, front and bottom access is usually all you need clearance for.
  • The technology involved with these on-demand units does have some moving parts, generally a dial which to set the temperature, and at least a flow valve to register the flowing of water. Some models include flow control valves which ensure that the heat is applied evenly and if demand exceeds the units capacity to heat it, the unit will reduce the flow to ensure constant temperature control.
  • Depending on you demand, these units can require significant power to keep the water hot when 2 showers and dishwasher need to run at the same time, our unit services 2 full bathrooms, 1 very busy kitchen, another unused kitchen at times and a laundry room.
  • Typical sizing for Electrical On-Demand units are 24Kwatt to 36Kwatt for a family of 4-6 people, where a 24kw system needs 2 x 50 amp circuits and a 36kw system needs 3x 50 amp circuits. If you understand the math here, the smaller 24kw unit can consume up to 24000 watts / 240 volts ac = 100 amps, that’s pretty much the full availability of the older homes if they’ve been upgraded to at least 100 amps, In actual fact the units don’t actually use that full 100 amps every time they are used, but on first demand, it’s possible.

    power Mon wh stepping
    Power Monitor showing Water heater power stepping
  • Electric on-demand units only apply enough energy to maintain your set point temperature, and employ a stepping process when turning on the energy to heat the water. The graph to the right is showing the actual power consumption of our test home with approx 700 watts of standby power and the rest is the On-Demand 24kw Electric Tankless water heater power draw. The scale range shown is actually from 12,000 watts to 13,600 watts, which is the typical draw when the ground floor shower is being used. You can see that the heaters power use steps up and down as is needed to maintain our constant temp of 115 degrees F. The peak of about 13,500 watts is only around half of this water heaters maximum capacity of 24,000 watts. When both showers or a shower and the dishwasher are demanding hot water, we see the range adjust to much higher levels.
  • The On-Demand units are also controlled by waterflow and therefore have a minimum flow requirement. Our test home also has another resource saving feature known as a water pressure regulator, used to reduce the city of Vancouver’s street pressure from around 75-90 psi down to about 45 psi. And as the home is much older, built in 1924, so is the 1/2 inch copper plumbing, and the buildup inside the plumbing associated to scaling and minerals in the water. Plus the addition of low flow shower heads, water restrictor washers, and a pressure balancing shower valve, when other cold water demands reduce the showers cold water pressure, it also reduces the hot water pressure to maintain similar cold/hot flow and temperatures, which we have found, can be below the Turn on point of the water heater. I’m not going to tell what kind of sounds come from a shower when the water goes cold.
  • When water flow isn’t an issue, and you aren’t storing hot water in a tank, these tankless units provide a seemingly endless supply of hot water. This feature has allowed our home to now enjoy a bath without having to boil extra water on the stove to sufficiently fill the upper floor soaker tub. But with this new feature it also no longer limits the length of showers that our family takes. This in itself can be a majour problem and totally negate the original energy saving plan you had when you choose this option. We used to end our showers early in fear of running out of hot water, we no longer live with this fear, and so time in the shower isn’t really counted anymore.

Highest Efficiency technologies like Heat Pumps, Hybrids and Thermal Solar

As the industry tries to expand its customer base, improve on efficiencies and provide consumers with more options, or perhaps simply to survive, they develop new products that do even more than we ever could imagine. The driverless car is already on the streets today, so why wouldn’t we expect state of the art tech in a water heater? The Heat Pump technology has been around for quite a long time, and as the cost of energy increases, the heat pump concept makes more sense. Almost all refrigerators and air conditioners use a heat pump to cool, but this same process works for creating heat too. The latest technologies today include some very impressive Heat pump/Electric hybrids and Thermal Solar/ Electric hybrids. As these units are in the arena of bleeding technology, as in they are integrating multiple systems into a single unit, they do expose the user to some additional risk, but time will heal this initial challenges and some of the manufacturers will bubble to the top, and other will not.

 

 

To understand the basics, a heat pump effectively extracts heat from one medium and compresses it with a gas to cool it, and in reverse, decompressed a gas to expel the cold. So the standard A/C unit in the window of an apartment does this whole process inside the single box, taking the heat out of the apartment, and blowing it outside. The Heat Pump water heater system, works generally the same way, in which you extract heat from air or solar panels, and use that heat to make your water hot. Keeping in mind that you must run a powerful compressor to move the gaseous material from one location to another such as a small radiator inside your car to the larger Condensing Radiator on the front of your car, aka a condenser.

I’m going to reference 2 units that are available today and are very good options for some of us right now. The Rheem Professional Prestige Series: Hybrid Heat Pump and the SunPump.  These 2 units differ as the Rheem unit is a replacement for your domestic hot water where the Sunpump is designed for your radiant floor heated home or a replacement for your hot water boiler system. Both use Heat Pump technology, one extracts heat from solar panels, the other extracts heat from air. Much like an office of building A/C unit has cool air radiators in the office and a heat condenser on the roof of the building with a gaseous connection between them, the Sunpump operates in a similar way, except it uses silent solar panels on the rooftop instead of a big box with a huge fan. And much like an apartment A/C unit in the window, the Rheem Hybrid Heat pump exchanges the heat through the air right on top of the unit itself, so if you don’t need any cold air inside your home, you simply run the air exchange pipe outside. Both of these units also have Electric heating elements for backup on extremely cold situations.

gas water heater
Natural Gas Water Heater

The Rheem Hybrid Heat Pump is a direct replacement for a normal Hot water heater with a tank, as it has it’s heat exchanger on its top, its likely going to be a little bigger than the unit you have today. And this unit will need some larger ducts to allow for the flow of fresh air, generally speaking you would connect both intake and outlet outside your home, but you might want to take advantage of the output cold air inside you house if its a hot summer day, or possibly extract the warmer inside air on the outlet in colder climates. These little tricks make this unit versatile, as the intake and output air is in no way contaminated, it’s simply used to help move the heat from one place to another, or in a water heater’s case cold from one place to another.

The Sunpump is a replacement for an existing boiler system that is generally much larger and has the capacity to also store some of the save heat

Sunpump

in a Hot water tank. The Sunpump extracts heat using roof mounted solar(evaporator) panels, and extracts the heat from the sun, and outside ambient air and condenses it to product the heat that is stored inside the appliance. although the Sunpump doesn’t currently connect directly to your hot water supply, that feature shouldn’t be far away and currently it’s a simple hot water heat exchanger hookup to your existing or stand alone water heater.

Considerations when making your choice for the right solution

So if your expecting me to tell you which option is right for you, I can’t, but here are some variables that will help you decide:

  1. If you don’t currently have natural gas in your home, it’s pretty simple, you are now down the path of electric, electric hybrid, or electric on-demand
  2. If you have Natural gas but don’t have a water drain nearby, then you’re either going electric or you’re stuck with a low efficiency NG water heater, high efficiency models use condensers which need a drain for water.
  3. If you want to save on cost of ownership investing in a Hybrid solution should pay off much sooner.
  4. If you want to save the planet for our future generations, you have 2 choices, Pay for Renewable Natural Gas or go high efficiency electric
  5. If you want to save space, or your needs are limited in size and real estate, the smaller On-demand units are the way to go
  6. If your home doesn’t have a nice new large 200 amp service breaker panel, you may want to stick with a water heater with a tank, so you can heat with less peek power draw, or the Natural Gas options.
  7. If you are building from scratch, talk to your designer and think about On-demand at each source, small electric units at each location simplify the home, you only run cold water plumbing to each area, you’re storing hot water and waiting for it to reach your tap, and this proven design works very well in many other countries.
  8. If you have or plan to have PV Solar panels, go electric.
  9. If you have or plan to have an Electric Vehicle, go electric and get PV solar.
  10. Very Important: Be smart, ask for advice and start with an Energy Audit to make sure you are spending your money on the right energy saving activity.