Eastern Electric

Case study · Commercial · East Lothian

Haddington: 40.2kWp ground-mount solar & 69kWh battery.

A full commercial package — ground-mount PV, three-phase battery storage, and a single-to-three-phase supply upgrade — cutting site electricity spend from around £40/day to roughly £5/day between April and September.

Sector
Commercial
System
40.2kWp PV
Storage
69kWh
DNO
G99

Overview

Eastern Electric delivered a complete commercial ground-mount solar PV and battery storage system for a client near Haddington, East Lothian, including the coordination of a site supply upgrade from single-phase to three-phase as part of the overall package.

The client operates two properties from the same site and was previously spending approximately £40 per day on electricity. The objective was to reduce grid import, make better use of available land, and store surplus solar for use outside peak generation periods.

A roof-mounted system wasn't the preferred option for this site, so a ground-mounted array was designed and installed to maximise generation potential.

76 Longi Hi-MO X6 530W panels on the ground-mount array
76 × Longi Hi-MO X6 530W panels — 40.2kWp ground-mount array.

The challenge

The site had consistent electrical demand across two properties — a strong case for on-site solar and battery storage. But the existing supply was single-phase, unsuitable for the scale of system required. Eastern Electric arranged the upgrade from single-phase to three-phase, allowing the site to support a larger commercial PV array, a three-phase inverter, battery storage and future electrical demand. A G99 application was required due to system size and export.

The solution

A 40.2kWp ground-mount PV system using 76 Longi Hi-MO X6 530W panels, connected to a Solis 40kW three-phase S5 inverter. Storage is provided by Fox 10kW three-phase AC-coupled inverters and 6 × Fox EP12 batteries — 69kWh nominal. The mount uses screw foundations rather than major concrete works — a practical fit for the site conditions. Battery storage captures surplus generation, reduces grid import outside daylight hours, and increases on-site use of the energy generated.
Solis 40kW three-phase S5 inverter and IMO DC isolators on the array structure
Solis 40kW three-phase S5 inverter with DC isolation, mounted on the array frame.

Technical specification

Solar PV capacity40.2kWp
Solar panels76 × Longi Hi-MO X6 530W
Solar inverterSolis 40kW three-phase S5
Battery systemFox AC-coupled storage
Battery invertersFox 10kW three-phase AC-coupled
Batteries6 × Fox EP12
Battery capacity69kWh nominal
MountingGround mount, screw foundations
Original supplySingle-phase
Supply upgradeArranged as part of the project
Final supplyThree-phase
DNO applicationG99
Fox ESS battery cabinets and hybrid inverter in the plant room
Fox 10kW three-phase AC-coupled inverter with Fox EP12 battery cabinets.
Second view of the Fox EP12 battery stack in the plant room
69kWh nominal Fox EP12 storage — sized to soak up surplus generation.

The result

Before

~£40/day

site electricity spend

Apr–Sep

~£5/day

after PV + battery

Oct–Mar

~£12/day

shoulder & winter months

Exported electricity is also used to help offset remaining costs, further improving the commercial return. This project demonstrates how a properly designed PV and battery system can significantly reduce electricity import for commercial sites with suitable land, consistent demand and the correct electrical infrastructure.

Key benefits

  • Electricity cost cut from ~£40/day to ~£5/day (Apr–Sep)
  • ~£12/day electricity cost the rest of the year
  • 40.2kWp of on-site solar generation
  • 69kWh nominal battery storage capacity
  • Battery storage increases self-consumption
  • Export used to offset remaining grid costs
  • Single-to-three-phase supply upgrade arranged in-package
  • Full three-phase commercial design
  • G99 DNO application completed
  • Ground-mounted where roof mounting wasn't preferred

Similar site? We'll scope it.

Commercial land, roof or mixed — we design, install and commission in-house across Scotland, including DNO applications and phase upgrades.

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