Solar and hot water heat pumps are the future! Let me prove it.

Many of us have become addicted to the convivence and comfort of our gas hot water systems.  ‘They’ve served us well’ you say, and only use the energy they need to heat our hot water.  We’ve been told that ‘natural gas’ is an important pathway to reducing our emissions, while also being an energy-dense resource which will power our nation for years to come.  I’m sorry to tell you but whoever sells you this story is all wrong!  

In Australia, over 2.31 million households now have Solar Panels humming away on their roof and generating clean green electricity throughout the day, making us rich on the proceeds without any effort, right?! Well not really. The reality is that wherever you live in Australia, when the bill arrives most of us are only receiving a small return.  The best advice is to use the energy you generate rather than export it.  Using the energy takes the pressure off the grid by keeping the voltage at an acceptable limit, and it’ll keep your inverter from tripping off when the grid voltage spikes in your neighbourhood from too much solar generation. In the long term you save money by using energy when you generate it which prevents you from double-dipping into the grid at a later time in the evenings when it’s more expensive.

So how does this all relate to heat pumps?

Before I get to that, I must first declare my interests… I love heat pumps, and this is why you should too!

Heat pump technology has been around since the Kelvinator refrigerator.  You already have one in your fridge.  In fact, modern hot water heat pumps use the same thermodynamic cycle and they operate by using a small amount of electrical energy (about 1kW) and a working fluid to absorb energy from the outside air and transfer this to a hot water storage tank. 

If you want to go deep, check out the YourHome website, it’s a descriptive yet plain-English approach to explaining all things home. 

What’s impressive about heat pumps is their efficiency.  Efficiency is important when 21% of all our energy in the home is used on hot water.  Heat pump efficiency is measured using Coefficient-of-Performance (COP), which determines how much heat is generated for every 1kWh of electrical energy input.  Most heat pumps have a COP between 3 to 5 which is impressive because It means that every 1kWh of energy in results in 5kWh of heat output.  Heat pumps have become even more efficient with the advent of CO2 refrigerants which operate significantly better in cooler climates than the old technology of CFCs.

Source: YourHome – Australia’s guide to environmentally friendly sustainable homes

So how do we harness the power of Solar Panels with the genius of heat pumps you ask? Heat pumps operate at their highest COP when the ambient air is at its highest.  Timing your heat pump to operate when your Solar Panels are generating the most energy, which usually correlates with the high temperatures of the day, means you’ll be heating your hot water system throughout the day.  Set the timer on your hot water heat pump to run when you’re generating the most energy from Solar Panels, and you’ll have hot water aplenty while minimising energy use from the grid and saving you $$.

If you scour the internet, you’ll find a whole bunch of calculators comparing emissions, operating costs and capital costs of gas, conventional electric hot water systems, and heat pumps.  These calculators can be deceiving because they assume heat pumps are powered by coal rather than Solar which means their costs and emissions are made to look much worse than they may actually be! If you’re interested in some hard data, check out this lifecycle analysis (LCA) study which compares all the hot water systems and their impacts.  Although this study uses grid-sourced electrical energy, the chart below shows heat pumps still have lower emissions than all alternatives.  

Source: Comparative GHGs of hot water heating systems in Australia

Thinking about capital costs, it is important to acknowledge that heat pumps are more expensive than gas and conventional electric upfront. Luckily, there are Small Technology Certificates (depending on where you live) which effectively act as a rebate, lowering said capital costs.

When choosing which heat pump to purchase (have I convinced you yet?!), choose a quiet heat pump with a high COP and a CO2 refrigerant.  Sanden have been leaders in this space for some time, but also checkout Earthworker Energy Co-operative who employ coal-displaced workers to manufacture Australian made hot water tanks combined with Reclaim heat pumps.  We are big fans of Earthworker here at EnergyByte and they’ll feature more to come.