Novo-Solar-Solutions-Hot-Water-Tank-into-Battery-Storage May 2nd, 2016

Novo Solar Solutions photovoltaic panels have been installed in different regions of BC both on and off grid. With our on-grid systems, solar panel customers do not need a battery system to store unused energy because whatever is not used is fed back into the BC Hydro grid. For off-grid installations, a battery system is needed to store the power and then draw from that on-demand.

Batteries have traditionally been setup using multiple deep cycle cell batteries in tandem. These batteries worked well but the space that these took up and the regular maintenance needed make it an imperfect solution to energy storage.

Telsa introduced 2 battery systems last year. The Powerwall 10kWh and the smaller 6.4kWh. But as of April 2016, Tesla discontinued the 10kWh as sales were lagging due to price and low demand. The larger Powerwall was intended for protection during power failures. The smaller of the two is used for solar power time shifting and can be cycled 5,000 times. So focusing on the smaller unit makes sense.

Why would you use a hot water tank as a storage battery?

What if you could use a household appliance that already exists in pretty much every home in BC as a home battery? For just a few hundred dollars, your electric water heater can be made to work like a battery at the fraction of the cost of a Tesla Powerwall.

Most water heaters hold 113-190 litres of water, with the largest holding 300 litres. These tanks can be powered by natural gas, propane or electricity. When a household has a large unit you may only need to heat up your water once a day as it will hold the heat longer. You can also choose to heat your water when electricity is the cheapest, which is usually late at night. Here in BC we do not have peak rates, like many jurisdictions, during certain times of the day but that doesn’t mean that it won’t happen in the near future. As we wrote back in Feb 2016 on our post titled, “Tesla Powerwall and Peak Demand

BC Hydro currently does not use Peak Demand Billing like most other utilities in the world. But it is more than likely that BC Hydro will adopt this billing scheme in the near future. If that happens our power bills in BC will increase dramatically. This change will make solar panels plus a battery system far more attractive to electricity consumers to capture their own electricity and store it for future use.

But even in BC where peak demand does not exist, does not mean you can’t take advantage of using your home hot water tank as a energy storage unit.

Solar power and your hot water heater

Photovoltaic solar panels stop generating power after the sun goes down, just as residential demand is ramping up. So there are two ways to fix this. You can extend the supply of surplus energy by storing it until it is needed at night. But as we mentioned before, storage can be costly and can usually only power a home for a few hours.

The second way to fix this is shift more of the demand to the middle of the day when the solar output is at its highest. Since hot water heaters account for 9% of residential energy usage, using your solar power to heat the water makes sense.

So when BC Hydro customers store energy in the form of heat, it now works like a kind of battery. This energy storage technique been used by rural electric cooperative associations in the USA for a few decades now. Keith Dennis, an energy efficiency expert at the National Rural Electric Cooperative Association says that a “196 litre hot water tank can store roughly 12kWh of energy. ” A new water heater cost around $1000 compared to a Telsa home battery that is $3500+ and only stores 7kWh of energy.

So when the sun is shining, the large capacity water tanks can be enabled to make immediate use of that energy to heat water to high temperatures. They can then be shut down when renewables are scarce.

All in all, this battery storage solution utilizes something the majority of people already have in their household and requires minimal setup.


If you are interested in learning more about turning your hot water tank into a battery storage, or you just want to tlak about a solar project, contact Mark Tizya at Novo Solar today.