35% of the energy needs of a household are consumed in the production of Hot Water. A tiny house generally has two or three uses of hot water in the bathroom, laundry and kitchen which is moderate to the traditional uses in most homes.
This design is attempting to meet off grid if not renewable energy techniques, which in our context are PV, solar thermal or thermal exchange technoogies. My preference is for PV given our relatively soouthern latitude and the need fora temporate winter climate as well as a hot summer.
I am shying away from viable LPG technology because they are a fossil fuel and more importantly they offer an additional danger in a dwelling used to be rented out to others. The danger of gas leak and the requirements for appropriate ventilation add an extra degree of difficulty.
Likewise thermal exchange techniology such as a wet back wood fuel heater really dont work in our climate. In summer we need hot water still but we dont need a heating stove.
Im planning to utilise the roof for a significant solar PV array. I have room for 12 or 14 350watt PV panels on the main roof which adds to 4200-4900 watts which far exceeds my likely power needs for this tiny house. However with hot water and solar airconditioning a 4kw system may be justified. Cost for PV panels$1500 – $1700 Hybrid Inverter $600 – $1000 depending on size.
There are solar PV technologies that allow direct connection of 3 or 4 solar panels to an electric hotwater system that is converted to 12 or 24volt. There are also load transfer devices that prioritise electric hot water heating over selling back grid connected power by sensing the grid connect or at a more basic level simply running the electric water heater in the mid afternoon when the PV power is most plentiful. A timer may cost $200 or a load sensing transfer switch may cost $500. The beauty of this is that they do not require off grid equipment running on 12 – 48v and this is attractive.
I am using a Rennai 80lt single element electric Hotwater service that normally retail for just under $700. I have purchased a brand new unit from a supplier of “Scratch and Dent” appliances for $244 delivered. The orange dot in the above photo is next to the “cosmetic imperfection” for this product – not bad for a $450 discount. It has a 3600 watt element but 1200 and 2400 watt 240 v elements are manufacturer options. I do understand that the graceful lines of a hot water service are a thing of beauty but I have never been one to object to a cosmetic imperfection for an appliance that I intend to keep hidden in a cupboard. Hopefully when it is delivered today I will not have second thoughts.
This HWS is 900 tall by about 500 wide. Im planning to put this in the hidden corner of our kitchen bench (which is also 900 high) however to fit I plan to drop down the floor level for its base by about 100mm of the 170 high floor platform so that it will fit. This is nice and central to the kitchen and bathroom where our plumbing needs to be.