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Outdoor Battery Solutions?

weoleyric · 2026-05-31T07:57:11Z

I'm interested in hearing about fellow forumites experiences with IP56 outdoor battery storage systems.For background, we've got an extensive home battery system on our small 3-bedroom semi-detached home already, including two main systems:-* SolaX X1 Hybrid Series inverter with 2 × SolaX Triple Power 5.8 kWh Batteries for a total of 11.6kWh. This system has an off-grid backup switch, and are fed by 12 x 365W solar panels on our roof. * 6 x Ecoflow plug-in batteries, including 2 × EcoFlow Stream Ultra X 3.8 kWh, 1 × EcoFlow Stream Ultra 1.92 kWh, 3 × EcoFlow Stream AC 1.92 kWh, for a total of 15.36kWh, fed by various DIY solar panels totalling 2.98kW. While the SolaX and Ecoflow aren't integrated and don't "talk" to each other, we use Home Assistant, Wonder Watt, plus an Ecoflow CT-clamp smart meter, and 2 x Shelly CT-clamp smart meters to monitor and manage the home usage. In terms of energy draws, we're running a Nissan Leaf EV, and a Hyundai IONIQ PHEV, and a Daikin ASHP with hot water tank (and Solar iBuddy). We have an 80A grid connection, and use the Octopus Intelligent Go tariff, with an Ohme Go Commander smart charger and an Ohme (dumb) EV charger. This setup works well and gives us 2330-0530 "cheap" energy (8p kWH) and some nice bonus "cheap" slots during the day (which WonderWatt takes advantage of to top up our batteries). This will be the first full year that we'll have had the above setup running, but in previous winters, the batteries didn't cover peak-time use of 35kWH during the day, peaking at 50kWH. So, we're exploring options to expand our battery setup to completely time-shift energy use, even during the coldest, darkest winter days. The challenge is:- * We cannot upgrade the Solax battery system, as it is both loft-installed and our existing installer isn't interested in lugging any more heavy batteries into the loft or for building safety regulations. * The Ecoflow system is limited to 6 x batteries, which we've already maxed out. * We have no more space for batteries inside our home, so are looking to outdoor units. Therefore, I'm wondering what our options are to add an additional 30kWh (or similar sized) IP56 rated battery system to an outside wall. I've been drawn to the Fogstar Energy 48V 40.96kWh IP56 Outdoor Battery System and Cabinet combined with a Victron inverter, but I'm sure there are other options. Our challenge is finding an installer who will work to combine a new system with an existing setup. Most installers seem to want "green field" sites where they can install a standalone system. Therefore, a secondary question would be, which technically competent and experienced installers (we are based in Newcastle-upon-Tyne in the North East) would forumites recommend for more complex installs. I appreciate the above is a fairly comprehensive setup, so feedback and suggestions gratefully received!

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EtchedPixels

(@etchedpixels)

Estimable Member Member

Joined: 3 months ago

Posts: 152

08/06/2026 4:53 pm

VAT Notice 708/6.

It's not as far as I am aware ever mentioned MCS and indeed many of the things it covers are simply not even MCS covered in the first place (eg draught strips).

For a vat registered operation the paperwork should be no more than usual for VAT. For a not vat rated operation I don't know but I doubt it's fun if it's even possible.

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Batpred

(@batpred)

Noble Member Member

Joined: 2 years ago

Posts: 1133

08/06/2026 5:37 pm

@etchedpixels

Thank you. From what I see, it covers all building trades. VAT registered contractors or subcontractors can supply and install items in the list free of VAT.

8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kW export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; Vaillant Arotherm Pro 7kW; 100Amp head, HA lab on mini PC

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Old_Scientist

(@old_scientist)

Honorable Member Member

Joined: 2 years ago

Posts: 545

09/06/2026 12:05 pm

Have you modelled the costs of switching tariff?

We have solar, battery and ASHP. Like you, our peak winter usage can approach 50kWh per day. We are able to cover this with a single Tesla PW3 battery at 13.5kWh (installed outdoors in the rain) by using the Octopus Cosy tariff which has 3 cheap rate charging slots.

The Cosy cheap rate is more than your current EV tariff, but we need a fraction of the battery capacity as we are able to recharge the battery 3 times per day so each recharge only needs to last 6h until the next available cheap rate slot. It also works well ion summer as a single 13.5kWh PW3 nicely covers a full day's usage (~12kWh) in summer, even if there is absolutely zero solar. We do not have an EV in that mix.

So for us the question was/is simple - would the cost of additional batteries be offset by moving to a cheaper overnight tariff (we could pretend we have an EV on regular Octopus Go). To achieve that, we'd need two or three PW3's so for us the smaller (cheaper) battery capacity works out better and gets us to the point of having zero bills (export in summer offsets import in winter)

There is also the risk that you may not see a return on capital if cheap overnight EV tariffs end (or prices normalise) as you now have large battery capacity that you can no longer cheaply fill.

This post was modified 3 months ago by Old_Scientist

Samsung 12kW gen6 ASHP with 50L volumiser and large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW). Net Zero

👍

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Batpred

(@batpred)

Noble Member Member

Joined: 2 years ago

Posts: 1133

09/06/2026 6:48 pm

For us, adding a 16kwh battery means a heatpump can reduce energy costs by 50% (instead of a 10% drop(. And since our £/kwh is significantly lower than Tesla's, it is a simple decision.

8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kW export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; Vaillant Arotherm Pro 7kW; 100Amp head, HA lab on mini PC

👍

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