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Tesla Powerwall Case Study: Phil Bixby

Aug 28, 2019

Phil Bixby takes energy efficiency very seriously. An architect who specialises in Passivhaus design, he recently retro-fitted his Victorian end of terrace home to a high level of energy efficiency, while installing an array of vertical solar panels, and a Tesla Powerwall mounted in a highly unusual place...

Phil and his partner Caroline moved into their two-bedroom home in York just under a year ago, having used Phil’s architectural expertise to bring the building closer to the high energy efficiency benchmarks of the German Passivhaus movement - designed to provide a high level of comfort while using minimal energy for heating or cooling. 

“It's based on principles of very high levels of insulation, very high quality external windows and doors, very high standards of air tightness and the incorporation of mechanical ventilation for heat recovery,” says Phil. “The basic thinking behind it is the space-heating requirements of the house or dwelling are sufficiently low that you are much less concerned about where your energy comes from.”

Phil, however, is concerned about where his energy comes from; it’s why he’s signed up to Tonik’s 100% renewable electricity, and it’s why he made his home even more sustainable by adding solar PV and a Tesla Powerwall. Furthermore, the high energy efficiency of his home means he doesn’t need to use gas for his heating.

“The way things are going with the energy mix of the UK at the moment,” says Phil, “it very much points you in the direction of considering electric as being a way of heating houses - and that’s what we’ve done here. While it's not zero carbon in itself, it's very easy to get to the level of being zero carbon by adding in renewable.

“Given that I'm an architect and passive house designer, I really feel like I should be walking the walk!”

Bixby Solar Panels

The installation

Having used Tonik’s in-house installers, The Phoenix Works, on previous projects for his clients, Phil was well aware of their renewable tech expertise and knew they would be up to the highly specialised nature of his project.

“I've always used Phoenix Works because Thomas [Newby] is always good to work with,” says Phil. “This building has a slightly unusual arrangement in that we have a south-facing gable wall where we wanted to install vertical photovoltaic panels, and a pitched roof on the back extension where we wanted in-roof installation.”

The appearance of the solar panels was a high priority, with Phil and The Phoenix Works collaborating to find ways that would incorporate them stylishly into the building’s facade. 

“I got Thomas to run some calculations on how effective the panels would be on the gable wall,” says Phil. “They showed fairly healthy numbers so we went for that. We finished it with some matching trim round the edges so it all looks like a nice dark grey wall that just so happens to have solar panels within it.

“For the installation on the back extension roof, we stripped all the slates off, put the solar panels up and then tucked the slates in to make it all look good. It gets quite a bit of attention - my office looks out onto the street so I occasionally get people peering through the window saying ‘Are those solar panels up there?’”

The solar panels aren’t the only unusually-mounted, attention-grabbing element of Phil’s super-efficient home, however. He had one particularly offbeat request that was an absolute first for us...

“We wanted our Tesla Powerwall up on the dining room wall,” says Phil. “Partly that’s because I’m an energy nerd, and if it’s going to give any heat off, I’d rather have that be inside the house - so we’re actually getting the benefit of that in winter. But partly it was because I quite like having it in the house so I can peer at it! People come in and see Tesla written across it, and everyone goes “Ooooooh!” in that way that they do, so I talk them through what it is.”

Phil Bixby's Tesla Powerwall

The impact

The Passivhaus retrofit served to make Phil’s home at least five times more energy efficient, meaning it already requires significantly less energy to heat than the average home. 

Unusually, all the heating is done electrically with a post-heater in the ventilation system warming fresh air that is pumped into the house. The only other heating in the home is provided by electric towel rails in the bathrooms and 1.5kW of electric underfloor matting. There is no gas heating whatsoever. 

“At the moment, as it’s summer, we’re not using any heating,” says Phil, “but we’ve got a whole house-worth of domestic plus my office running on the solar and the Powerwall. Quite often we’re running on no imported electricity at all, and are actually net-exporting much of the time.

“The worst case in winter for our place here is around 30-40kWh of electricity bought from the grid per day,” says Phil - a saving of up to 18kWh compared to the UK’s national average for daily consumption in winter. On top of that, Phil made sure when signing up to Tonik to select an Economy 7 tariff - so he could programme his Powerwall to charge up with cheaper energy at night when needed.

“The Powerwall will check ahead, work out if the weather’s going to be crap the next day, and if it is then it'll charge up overnight,” says Phil. “In that situation, we're generally getting from the end of the Economy 7 period at 7am through till three or four o'clock in the afternoon on using the battery. The only requirement then is just an evening’s worth of full-whack grid if we’re heating and cooking.”

With Phil’s office located in his house, he and Caroline are at home 24 hours a day, 7 days a week, using electricity for food, warmth and running an electric bicycle. Yet with their solar panels and Powerwall working together, they are making some major savings on their energy bills.

Phil Bixby's Tesla App

“I'm still waiting for a full year’s worth of figures in on it,” says Phil, “but we're looking like being somewhere between 33% and 50% of our energy coming from solar, a fair chunk of the rest of it then coming from economy 7, and just that remaining bit coming from using full-whack electric. It looks like our overall energy bills - once you take into account the feed-in-tariff that we get back - will probably be somewhere around £700 a year.”

Perhaps the biggest impact of Phil’s energy-efficient home, his renewable generation and his battery storage, however, is emotional: the feeling he gets from being energy independent and minimising his carbon footprint.

“Smugness is the word, really,” says Phil, laughing. “No, this has actually very much been a joint journey with my partner Caroline, in terms of designing the place and how we want it to work. She has no particular involvement in design or architecture, but she’s absolutely in love with our home because it’s such a pleasant place to live. The house just chugs along comfortably without us really needing to do anything, and we have the knowledge that I can easily report on a regular basis ‘Oooh, look! We’ve only used “x” amount of electricity in the last however many months.

“I regularly tap the device on the wall in the kitchen just to see what the system’s doing, and it's a nice feeling knowing that we’re able to live comfortably without burning any gas or using huge quantities of electricity from the grid.”

This is next-level sustainable living - bringing together the philosophy of Passivhaus energy efficiency with solar panels and battery storage - for a home that is as close to zero carbon as you can get. 

Welcome to the future of energy, Phil.

To find out more information visit our Tesla Powerwall page, or to book your Tesla Powerwall installation, call The Phoenix Works on 0113 815 5366.


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