Meet Maslow - The UK's Answer to Tesla's PowerWall

by @edent | , , , , , | 15 comments | Read ~9,772 times.

Even in the depths of British winter my solar panels'll still happily convert what little sunlight we get into delicious, free-range, organic electrons. Nice!

Most of our domestic energy use is in the evening. So, when I'm out at work I can schedule the tumble dryer, robot vacuum cleaner, and WiFi rice-cooker to consume energy when the sun is shining. The rest is sold back into the grid for my neighbours to use.

Wouldn't it be great to capture that energy and use it to power my lights and games console in the evening? Yes! Enter the Maslow - a 2kWh wall mounted battery designed to capture solar power and put it to use when it is most needed.

The Maslow gobbles up the surplus power and stores it for later use.


I received a subsidised Maslow battery as part of Project ERIC.

Project ERIC (Energy Resources for Integrated Communities) is an initiative bringing solar PV power and smart energy storage to up to 100 homes in Rose Hill, East Oxford. Project ERIC is led by Moixa Technology and Bioregional and is part-funded by Innovate UK.


It's a relatively svelte box - smaller than a normal domestic boiler - and fits neatly onto my interior wall.

Here it is before installation and without any batteries.

Maslow Unassembled-

As you can see, the batteries are designed to be replaceable. If they die unexpectedly, or technology leaps ahead, you should be able to keep your existing installation and just swap out the cells for something newer.

Maslow Removeable Battery-

A couple of screws - and a bit of swearing - and it was fitted.

Maslow Mounted-

Installation took around 3 hours. The battery needs its own RCD in your consumer unit. A few holes had to be drilled in order to get all the wiring hidden away.

Maslow Fitted-

The fans on the side run when the batteries are charging or discharging. They're a little louder than a typical PC - and will be easily drowned out by a boiling kettle or rumbling tumble-dryer. You probably wouldn't want this installed in a bedroom or living room - but it's fine for a kitchen or loft.

They're needed for cooling these chunky capacitors.

Maslow Capacitors-

Down in the bottom of the unit, you'll find the fairly unremarkable control circuitry.

Maslow Circuits-

Wait... wait a moment! Is that...? OMG! This thing is RASPBERRY PI POWERED!

Maslow Raspberry Pi-

Wooo! I think this is the 5th Pi I have controlling something in my home ?

There's a WiFi antenna which runs to the outside of the unit. You can also connect directly to the Pi's Ethernet port if you don't have a strong WiFi signal.

Hidden behind a panel is a full range of blinkenlights.
Maslow LED-

A mini-USB port is present for debugging purposes, along with some diagnostic LEDs. Apparently there's also Zigbee for controlling smart appliances in the future.

Network and API

As part of the Project ERIC trial, I've agreed to have my battery's energy usage monitored.

The Maslow collects details of usage every minute, these data are then combined to provide an overview of what our village is consuming and producing:

I also get access to a personalised dashboard - which will hopefully show more details soon!
Maslow Status-fs8

There's nothing really to control on the battery - it just sits there doing its job. There is an API, more details in a future blog post!


Because I'm on a trial of this hardware, the total cost of the Maslow battery and installation was £600 (including VAT@ 20%).

What do you get for that?

A typical mobile phone battery holds around 0.015kWh. My electric car has a battery capacity of 19kWh. My house's idle usage overnight (lights, chargers, servers, devices on standby) is around 100 Watts. So a typical night (2200 - 0600) will use around 1kWh.

My electricity costs me 13.08p / kWh - sign up to Ovo Energy and we both get a £25 Amazon voucher.

So, assuming the battery is fully charged once during the day and then fully discharged overnight, how long before the device pays for itself?

£600 / (£0.1308 * 2) ~= 2,300 days.

2,300 / 365 = 6 years 4 months.

At the unsubsidised price of £2,000 the repayment period is around 21 years. That's essentially the guaranteed lifetime of most solar-power systems. It also assumes that energy prices stay static.

Of course, the solar panels don't always generate enough - let alone enough surplus - to fill the battery:

There's no doubt the Maslow is an expensive "lifestyle" product. It's for saving the planet rather than fattening the wallet. Built in to the cost of a typical home it could be a real game-changer in how energy is used in this country.

As an aside, the UK Government pays me for every kWh the solar panels generate. They don't measure the actual amount I export. So the Maslow doesn't reduce the Feed In Tariff (FIT) payments.


OK, other than offsetting my grid usage, what does this big ol' box do?

  • Powering DC lighting. I decided not to go for this option. I already have energy efficient bulbs, so the extra cost for replacement didn't make sense for my needs.
  • DC Power Circuitry. I've not yet installed this, but it should let me charge USB devices without needing to do a costly AC/DC conversion.
  • Works during a power-cut. For safety reasons, the Maslow won't power normal household sockets during a power-cut, but it will allow you to use the aforementioned USB sockets and LED lighting. Handy in an emergency
  • WiFi for monitoring usages. Which of course means…
  • An API available for HACKING!


There are number of alternatives to this sort of technology.

Tesla Power Wall Batteries

Tesla battery has the cachet of the Tesla brand - but hasn't yet been released to the UK public. At around US$3,000 for a 7kWh model, the cost/power ratio is pretty good - but it is significantly larger in size to the Maslow.

The Tesla is only generally available in the USA, so it will be very interesting to see what their price is for the UK market. The Maslow is designed for typical UK use, which may be different from Tesla's focus - UK houses don't tend to have air conditioning, for example.

Final Thoughts

I've only just had the batteries installed - but it's obvious that the Maslow provides a vital way to reduce peak grid usage from domestic properties. Even if it is a little costly.

I'm delighted to be part of such an innovative trial - I'd love to see every home in the UK generating and storing their own energy.

15 thoughts on “Meet Maslow - The UK's Answer to Tesla's PowerWall

  1. Great blog & thanks for participating in the ERIC Pilot.

    On the payback, Moixa's unique UK GRIDSHARE service also offers (non pilot) purchasers £75 back a year on a rolling 5 year contract. This is possible via Moixa's GridShare Virtual Power Plant service, which can access income from network and national grid opportunities. This helps improve payback, providing end users - the daily solar benefit you mention + a grid share income. In addition as more new time tariffs appear, there should be additional benefits but is likely to involve switching tariff/utility.


    1. Bruno says:

      I'm thinking it would be more useful to use as a storage device to store off peak energy (cheap) at night and use it during the day. The solar panels are already doing their job and that gets sold to the grid, so I don't see much use in storing that: You're just creating an inneficiency.

      Removing usage from peak times on the other hand is already an environmental friendly way to reduce solution when all those wind turbines are spinning and peple are asleep - in fact one doesn't even need to have solar panels to do so, just the battery.

  2. Malcolm says:

    It should be possible to draw power from your EV. This is already in place for Nissan. Other manufacturers should offer this functionality. Probably not enough profits for them.

    1. Terence Eden says:

      I can plug anything I like into the car's USB sockets 🙂

  3. C Neale says:

    Did you mean its own MCB?

    Doesn’t this typically have an AC to DC conversion step that the Powerwall eliminates?

    Tesla Powerwall is available via Solar Plants in the UK.

    1. Terence Eden says:

      > Did you mean its own MCB?


      > Doesn’t this typically have an AC to DC conversion step that the Powerwall eliminates?

      I'm not sure how the Powerwall manages it. In the UK, my understanding is that all generation has to be metered and fed into the mains first. I may be wrong.

      Looking forward to UK companies actually installing some.

  4. Maslow says:

    tesla is an example, like several Chinese products , that are DC coupled - and fitted between PV and inverter. This avoids a DC to AC charger but has potentially significant losses
    - solar is stored in battery before generation meter, so dc/dc losses and battery losses can reduce metered FIT payment so less money
    - no AC to DC stage means it cannot be mains charged (as would mess up the metered generation) so cannot access winter smart tariffs or night tariffs so significantly reduces the benefit case down to only solar consumption . This is why most European installations are AC coupled like Maslow as Europe is really a solar charge plus winter battery for peak shifting and grid service model. Though DC coupling had tax relief benefit in US and is ok in very high solar locations where purpose is only self consumption
    - needs a specific new inverter so generally is new install only or retrofit is more complex as replaces inverter or impacts warranty

    There is a BRE and BpVa paper on benefits of AC and DC coupling and also a consumer advice paper

  5. Matt says:

    Very interesting article. There is also a 3rd option it's called PowerVault but it uses lead acid batteries so has a limited life time and limited discharge capacity. What sort of batteries are in the Maslow ?

    I think these types of devices will be great in the future when the price comes down, but right now splashing out £2k or more for one of these seems like a real waste of money to me... I have a 9kWh leisure battery bank and inverter that I charge up during the day from solar power and at night I use it to power my computer equipment as I have a server running 24/7 as well as several switches, modems etc so my computing for the moment has no daily running costs saving me about £100 a year which in 2 years will have paid for itself in terms of cost of batteries. What I really don't understand is the pricing for these things... where do they get £2k from ? Assuming the customer has no understanding of wiring two / three leisure batteries together to a charger and inverter? I paid about £300 for my bats + inverter and I already have the capacity to charge batteries using my solar inverter.

    1. Terence Eden says:

      Most people will not have the experience (nor the certification) to wire something like this directly into their home.

      I agree that the price is too high at the moment to make it economical - but if you assume a few hundred pounds for the equipment, the same again for an electrician to fit and certify everything, plus the cost of updating the software and maintaining an online portal, and a little profit for those behind it - the price is easy to understand.

      Ultimately, I think devices like this - solar power, storage, monitoring - will be built into new houses where the upfront cost can easily be absorbed.

    2. Oliver says:

      Hi Matt. Which batteries do you use for the 9kWh battery bank?

      At the moment I’ve got a single 100w panel and a 70Ah lead acid leisure battery (with a Victron 75/15 controller) which I would like to expand into a larger system.

      I’d be interested to know where you got your batteries from and if you’d recommend a particular brand/make.

      Also, which inverted are you using? Is it a pure sine wave type?

      So far I’ve been sticking to DC only and use this system to charge USB powerbanks, which in turn I use to power my portable devices. I know there’s losses with DC-DC conversion but figured it was better than a DC-AC-DC process.

  6. Eileen Millar says:

    Nowhere is there mention of the Maslow recharging from the grid (unless I've missed it). We met a representative who explained all the benefits of the system plus said when the batteries are emptied, ie: evening use, it will recharge from the grid!
    We thought this system was really good and would have gone for it but for the price.

  7. Alistair Gilbert says:

    How long are the batteries guaranteed for? The reason I ask is that I test drove a Tesla and it was a fantastic car, but I would not buy it because, when asked, they told me that a replacement battery set would be £25,000 (about a third of the price of the car!)

    1. Terence Eden says:

      Hi Alistair, I'm not sure on the guarantee - you'd need to ask Moixa. That said, reports from electric cars show that the degradation isn't as bad as some people feared. See

      The Maslow has a battery management system which should prevent any severe stresses. And, I hope, bigger batteries will be cheaper in the future.

  8. Terence,
    Useful article - just starting to get my head around the figures
    Have you looked into using an EV as part of the battery storage mix - using a two way charge / discharge system ?
    I have the opportunity to charge at work (from PVs) and was idly wondering if I could use some of this (say 5kWh) to use at home during the peak time !

    1. Terence Eden says:

      I have an EV - a Renault Zoe. I use it as storage but at the moment neither the car nor the electrical regulations allow for power to go from car to grid. I'm sure this will change in the future.

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