Futureproofing with Powerwall

Our desire to go green started off the back of Blue Planet 2 in 2017, and the ending sequence with huge amounts of plastic in our oceans. With more reminders and more awareness raised in the media about our impact on the planet, it was hard to look away and got me thinking.

At the same time, moving to solar also started to make sense from a purely financial point of view. The price had come down in recent years and when I came to renew my fixed energy tariff, it was 30% higher than before and I couldn’t afford for that to happen every couple of years. Then in early 2017, I was made redundant and having a small pot of money to spend on the initial outlay joined the dots for us.

We spoke to an installer about our needs. We wanted to demand less from the grid by generating our own power but needed to be able to store it too as we have very little demand during the day. My new job is in an office and we are also a host family for Norwich City Football Academy programme. Lads who aren’t local to the area stay with us, up to four at one time and when they are back from a days training, there is a huge drain on electricity to support TV, gaming, device charging etc, the household demand goes up substantially but by then we have lost the sun and so I wanted to be able to store and use past the point of generation.

Our installer suggested a couple of battery options and we chose the Tesla Powerwall because it was the best price per kWh and the biggest at 13.5 kWh which matched our high usage, between 10-15kWh per day. We also decided to switch to an electric car too, which would see this usage rise.

We have a 5.2 kWp east facing array and so generate a lot in the morning and then use it from the Powerwall in the evening. We call that summer mode and we’re self-powered around 98% of the time. This winter, we switched to the time-based control setting on the app to make use of the time of use tariff, this switches the Powerwall to charging from the grid when it’s cheap. I have also recently moved to the Octopus Go tariff designed with EV owners in mind who supply electricity for 5p/kWh between 00:30am and 04:30am every day. This allows the car to be charged for a very cheap rate in the autumn/winter months when solar generation is not sufficient. It also allows the ability to charge the Powerwall fully for about 70p and then use it to power the house for the rest of the day. That is a financial game changer.

I love the app as it allows you to monitor and you can input the exact times of your cheaper energy rate. I also like the fact that Powerwall is future proofed. They can be linked so if we get another EV, for example, we can add another Powerwall if we need to store more energy.

In our winter mode, we are self-powered 93% - 25% solar and 68% off-peak rates and the other is from the car topping up from the grid directly. In the summer, we are self-powered 98% from solar with Powerwall charged from solar alone.

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