24/7 Emergency Call-Out

Home » Products & Services » Generator Types & Ratings Explained
Generator maintenance

Reliable Power. No Downtime. No Crisis.

When it comes to power, every decision matters. Your generator isn’t just a piece of equipment; it’s the backbone of your operations when the grid fails or when you need continuous supply. Choosing the right rating ensures efficiency, compliance, and peace of mind.

At Shenton Group, we take the complexity out of generator specifications. From emergency backup to continuous power solutions, we break down the key ratings and standards so you can make an informed choice that fits your application perfectly.

Generator Power Ratings

Emergency Standby Power (ESP)

Emergency standby power is defined as the maximum power available during a variable electrical power sequence, under the stated operating conditions, for which a generating set is capable of delivering in the event of a utility power outage or under test conditions for up to 200 h of operation per year, with the maintenance intervals and procedures being carried out as prescribed by the manufacturer, as per BS 8528-1.

Ideal for: Hospitals, data centres, and commercial buildings during grid failures.

Why choose ESP?

  • Cost-effective backup solution without full-time power investment
  • Keeps critical operations running during outages

Prime Power

Prime power is defined as being the maximum power which a generating set is capable of delivering continuously while supplying a variable electrical load when operated for an unlimited number of hours per year under the agreed operating conditions, with the maintenance intervals and procedures being 
carried out as prescribed by the manufacturer, as per BS 8528-1.

Ideal for: Construction sites, mining operations, and off-grid facilities.

Why choose Prime Power?

  • Handles variable loads with short-term overload capability
  • Reliable for continuous use in challenging environments

Base Load
(Continuous) Power

Continuous power is defined as being the maximum power which the generating set is capable of delivering continuously while supplying a constant electrical load when operated for an unlimited number of hours per year under the agreed operating conditions, with the maintenance intervals and procedures being carried out as prescribed by the manufacturer, as per BS 8528-1.

Ideal for: Industrial plants or telecom hubs requiring constant power.

Why choose Base Load?

  • Eliminates risk of power fluctuations
  • Designed for stability and efficiency


Why Ratings Matter

  • Compliance: ISO, DIN, and BS standards ensure reliability and safety.
  • Performance: Correct rating prevents overload and extends equipment life.
  • Cost Efficiency: Avoid oversizing or undersizing for your application.

Technical Considerations

  • Load Acceptance: Some engines handle load changes better than others.
  • Ventilation: Proper airflow prevents overheating, our designs include ductwork and inline fans.
  • Flue Dilution: Combines exhaust gases and hot air into one discharge system, simplifying installation and reducing costs.

Why Choose Shenton Group?

  • Proven Reliability: Generators tested to meet rigorous safety and performance standards
  • Expert Guidance: We simplify complex ratings and compliance standards
  • Custom Solutions: Tailored power packages for your unique application
  • End-to-End Support: From design and installation to maintenance and compliance

Not sure which rating you need?

Speak to a power expert today

Contact Us

Our FAQ’s

Speak to a Power Expert Today

Get in touch today and book your free site assessment.

Contact Us
  • D

    Derek Sidaway – Sedgwick International UK

    Professional, efficient, courteous, I cannot praise the company and the staff enough. Our project was to remove a generator and associated control equipment from site, couldn’t have gone any smoother!
  • A

    Andy Hughes, Chief Technology Officer – Intelligence Hosting Services Limited

    After having major issues with a so called “Generator Specialist” we needed to find a company that was competent in ensuring our backup power facilities were installed correctly as well as safe. After speaking with Shenton Group over the phone, an initial site survey was carried out along with the works that were needed to … Continued
  • P

    Paul Hamblyn – Managing Director and Chief Operating Officer of EuroSite Power.

    Shenton Group have been a trusted partner since 2012. Their knowledge of the TEDOM CHP product proved invaluable when commissioning this complex project for CEFAS (Centre for Environment, Fisheries and Aquaculture Science), helping us to achieve the objectives set by our client.”

Our Latest News

  • Case Study: Powering 150 Fibre Network Sites with Uninterrupted Power Solutions

    Location: NationwideClient: Leading National Fibre Network ProviderEnd User: Businesses and Consumers NationwideSector: Fibre Network Infrastructure Products/Services Used: Client Overview Our client is a leading national fibre network provider operating across 190+ sites. They deliver high-speed connectivity to businesses and consumers, relying on resilient power infrastructure to maintain continuous service availability. Their operations are critical to … Continued

  • Case Study: Shenton Group Provides Reliable Power to Global Biopharmaceutical Distribution Centres

    Sector: PharmaceuticalsLocation: Liverpool Products/ Services Background A global biopharmaceutical company, based in the north west of the UK, was expanding due to the increase in demand for pharmaceutical supplies during the COVID-19 pandemic. Further manufacturing and cold storage were required on-site, and temporary power was needed for this expansion. Project Overview Shenton Group was tasked … Continued

  • Case Study – Porton Science Park

    Client: Wiltshire CouncilSector: Local AuthorityLocation: Porton Down Products/Services Background Porton Science Park provides a platform for Science and Technology to innovate in an environment that welcomes and supports new business start ups. Working in partnership with Wiltshire council and DSTL (the Ministry of Defence’s Defence and Science Technology Laboratory), who are an existing customer, Shenton … Continued

  • Case Study: Amazon Distribution Centres

    Client: Amazon Direct Sector: Distribution Location: Tilbury Products/ Services Background Amazon Direct is one of the largest distributors in the UK with over 30 warehouses operating currently. In 2021 an unplanned service requirement arose in one of Amazon’s distribution centres, which resulted in the requirement for a rental generator. Shenton Group were asked to provide … Continued

  • Backup Generator Solution for Ilona Rose House

    Client: Gratte BrothersSector: Mixed-Use Development Location: Soho, London Products/Services Background Ilona Rose House, set in the heart of Soho, London, is a 31,0,00sqm new-build project spread over 13 floors, including four below ground. With a build cost of £100m, the development will contain shops, restaurants, bars, offices, residential apartments, a gallery and a nightclub. Shenton Group … Continued

  • Providing Power Continuity to Virgin Media

    The Virgin Media Technology Service Centre, a campus facility in Knowsley, UK, was subject to technical upgrading of its supportive infrastructure to better enhance the power resilience to the site.

    The existing Diesel Rotary Uninterruptible Power Supplies (DRUPS) technology became extremely expensive to maintain, leading to the decision to upgrade the equipment. Shenton Group was once again entrusted with this project due to an ongoing relationship with previous power installations for Virgin Media.