A company begins because the founders think they can give the world something new, or at least something better than what’s already out there.

That initial spark can come from many places: existing experience as a consumer, knowledge of a particular industry, it could be mission-driven, or it could just be a hunch that they can make something cool.

Our idea

At Windfall Energy, the short version of what we’re doing is making a home battery aimed at renters and people living in smaller homes. That’s about half of the UK, including us.

As people living in flats in London, we wanted to do something about our rising electricity bills and be able to use more clean energy, but we can't install solar panels or make costly, permanent changes to our homes.

Without the option of solar, the idea was to use a battery to store cheap off-peak electricity overnight, and then use it the next day during peak times.

Our initial hypothesis was that there wasn’t really anything out there aimed at us. So we set out to test that and get a fuller understanding of exactly what’s already available.

What we though might work for us is something between a big “white-box” home battery and a portable camping battery.

Big “white-box” home batteries and a portable camping battery

What’s out there

Existing “white-box” home battery systems are simply too big for a small flat. Both in terms of energy capacity and in terms of being impractical or impossible to install.

Smaller “portable” batteries show more promise, but can they do what we want them to do?

This is where the focus of our evaluation has been. We’re particularly interested in a new class of batteries coming onto the market in Europe over the last couple of years. Especially in Germany, where "Balkonkraftwerk" is a new term referring to small, plug-and-play solar power systems designed for apartment balconies.

So we’ve been testing existing batteries that are already on the market and seeing if than can work for us. The short answer is that they almost do.

In terms of size and capacity, some of the batteries we found are much more appropriate for London flats. They’re about the right capacity to charge for a couple of hours in the middle of the night, and store enough energy to offset the daytime peaks.

The two key weaknesses for us are the expectation that they’re integrated with solar panels, and the overall useability.

No solar please

As I’ve said, our concept is for people who can’t have, or don’t want, solar. For many existing batteries, the solar component adds complexity from a technical point of view and from a useability point of view too. For example, I marked up the quick start guide below to show which parts of it were about adding solar inputs. For my setup, barely a quarter was relevant to what I needed to do.

Of course, that doesn’t necessarily make it a bad product, just one that isn’t ideal for our use case.

Our testing has also uncovered a more subtle, and fundamental, consequence of the focus on solar input. These batteries are very inefficient, and we think there are a couple of reasons for this.

Firstly, if you’re getting “free” electricity from solar, it’s perhaps less important what the core efficiency of the battery system is. And you would never really be able to measure it anyway.

Secondly, these products are pretty cheap, with power electronics not optimised for daily charge/discharge like we need. They’re trying to do a bit of everything, and end up not being able to do anything as well as they could.

For the Windfall Energy use case, round-trip efficiency really matters to us and we can do much better with our design considerations.

User experience

We take useability for granted when it’s good, but when it’s bad it makes you want to throw things out of a window. Thankfully for everyone, these batteries are too heavy for that.

Again, some of this is to do with these batteries trying to do lots of things and not really having a tightly-focussed purpose. That’s not an excuse though - they should be able to handle things much more elegantly and mostly it’s just bad design.

When setting up one of these batteries to test, I took screenshots as I went along. The screens below weren’t even all of them, but I think it shows what a bloated and overly-complicated process it was.

A recurring theme was that I just didn’t know what was going on with the batteries. My mental model of how things were working was clearly misaligned with the system model. Don Norman would have a field day.

My struggles weren’t helped by key options such as the “Operating Mode” being called different things in the app UI, in the printed manual and in the online manual.

Another common thing I noticed was apps adding new “AI functionality”. Doing this before the basics have been well addressed just added complexity, rather than reducing it.

With the help of hacks and workarounds found on Reddit, in the end I could almost get things working as I wanted, but it was a painful experience.

Total Product Concept

I haven’t even mentioned the struggles we had simply ordering these batteries.

The ordering and delivery processes are great examples of the Total Product. Also known as the Whole Product Model it’s about customers seeing a product as more than just its core functionality. Shipping, user manuals, warranty and customer support are all important aspects of a user’s perception of a product.

Total Product Concept, adapted from Theodore Levitt

Our approach

A Windfall Battery fundamentally needs to save people money, but in our product development process we need to think about much more than that.

The premise may be simple: a small home battery that charges up when electricity is cheapest, and then discharges to your home when it needs it. But it’s a complex product involving chemistry, mechanical engineering, electrical and electronics design, firmware, mobile software, cloud software, and IoT connectivity. Not to mention environmental, safety and regulatory compliance.

We need get all those things right, and we also need to care about how the products looks and how it makes users’ feel.

The reason we’re doing this is that nothing out there exists already. Not only is it something that addresses our own needs, but also the needs of millions of other people living in flats or renting.

Next time I’ll talk about our approach and how we’re going to develop the only battery designed for flats.

Searching for a Battery for a Flat Has Left me Flat