Project Summary
Client: Mercer Engineering Limited, Stockport
System: 180kWp commercial solar PV with peak demand management
Completion: Winter 2024
Annual Savings: £42,500
CO2 Reduction: 32 tonnes per year
The Challenge
Mercer Engineering operates a precision machining facility in Stockport, manufacturing components for aerospace, automotive, and industrial customers. The 4,500 square metre factory operates two shifts daily with substantial electrical equipment including CNC machines, automated handling systems, compressed air generation, and HVAC for the controlled-temperature production environment. Annual electricity consumption of around 850,000 kWh was costing the business approximately £255,000 per year, with peak demand charges representing a significant portion of this total.
The business had two principal drivers for considering solar PV. First, several major customers had introduced sustainability requirements into their supply chain, with carbon footprint reporting becoming an increasingly important factor in tender evaluations. Second, the volatile energy prices of 2022-2023 had highlighted the business's exposure to grid electricity prices and the need to develop more predictable, controllable energy costs.
Our Solution
Our engineering team developed a 180 kWp solar PV solution using 450 high-efficiency JA Solar panels installed on the factory's substantial roof area. The roof's relatively shallow pitch and unobstructed south-facing aspect provided excellent conditions for solar generation, with the system designed to maximise generation during weekday daytime hours when factory consumption peaks.
For inverter equipment, we specified Fronius string inverters with detailed monitoring capability. The Fronius equipment provides exceptional reliability and includes integrated power quality monitoring — important for a facility with sensitive precision machining equipment that requires stable voltage and frequency. The monitoring system integrates with the factory's existing energy management dashboard, providing real-time visibility of solar generation alongside other utility consumption.
One of the most innovative aspects of the design was the integration of solar generation with peak demand management. The factory's electricity contract included substantial capacity charges based on peak demand during the year. By correlating solar generation with production schedules, we could reliably reduce peak demand by approximately 80 kW, delivering capacity charge savings of approximately £14,000 per year — separate from the direct energy cost savings.
Implementation
The installation was completed over four weeks, with our team working closely with the factory operations team to schedule activities around production demands. Significant project elements included roof condition survey and minor remedial works, structural assessment confirming spare load capacity, installation of mounting infrastructure across the roof area, panel installation in optimised east-west and south-facing arrays, electrical infrastructure including a dedicated solar supply panel, and grid connection arrangements with Electricity North West.
The grid connection process required particular care given the existing electrical infrastructure at the factory. Our design team worked with the factory's M&E consultants to ensure the new solar circuits integrated cleanly with the existing distribution system, including provision for future expansion and potential battery storage addition.
Results and Performance
Following commissioning in February 2024, the system has performed in line with our predictions. Projected first-year generation is approximately 152,000 kWh, of which over 90% is consumed directly by the factory operations. Combined with peak demand reduction and capital allowances, the projected post-tax payback period is approximately 4.5 years.
Beyond the financial benefits, the installation has had immediate impact on the business's sustainability credentials. The 32 tonnes per year of CO2 emissions reduction has been incorporated into customer reporting and was specifically cited in the recent successful renewal of a major aerospace contract worth approximately £2.5 million annually. Mercer Engineering's leadership has also reported that the visible solar installation has positively impacted recruitment, with several recent hires citing the company's environmental commitment as a factor in their decision to join.
Client Feedback
"Nova Volt understood our specific requirements as a precision engineering business and delivered a solution that addresses both our cost and sustainability objectives. The combination of direct savings, peak demand reduction, and customer credibility has delivered far greater value than we initially expected. We'd recommend them to any UK manufacturer considering solar PV." — Managing Director, Mercer Engineering Limited
