CPSS Systems vs Standby Generators: 7 Reasons Why CPSS are More Cost Effective

Power Control
02 Aug 2022

Over the past decade, uninterruptible power supplies (UPS) and battery technology have advanced to achieve longer runtimes and meet specific safety regulations. Previously, standby generators had to be specified to meet runtimes required for life safety systems including emergency lighting, fire safety systems and firefighting lifts. However, modified UPS called *‘Central power supply systems’ (CPSS) easily achieve 30 minutes up to 3 hours runtime making them a viable option for backing up life safety systems instead of standby generators.

* CPSS compliant with BS 50171;2001 are allowed and used widely to support various Essential Service life Safety Loads up to 960Kva

These improvements have come at a critical time as many cities are tackling the environmental crisis by cutting down on the emissions that they allow. Initiatives such as the Environment Act have made diesel generators a less appealing backup power solution. Coupled with the lack of outdoor space in cities for diesel tanks, UPS and CPSS are becoming more attractive to most specifiers and consultants.

However, this shift has been met by resistance from some building surveyors who are insisting the cost of installing a UPS or CPSS over a generator is too much. Although the initial costs may be slightly higher, the additional hidden costs associated with generators are often overlooked.

When building a cost analysis for critical infrastructure using a generator, several considerations must be made.


  1. Exhaust Venting

The exhaust fumes of a generator must be vented which can include many meters of ducting which must avoid disturbance to nearby people whilst ensuring that fumes are minimised and vented safely.

If any part of the exhaust pipe passes through a building, it must be lagged to minimise issues with heat and fumes and additional precautions are needed if the exhaust pipe passes through or is attached to a building. Long exhaust pipes call for an increased cross-sectional area of the pipe.

Refilling the generator and storing the fuel and refill tank must also be considered.


  1. Cooling

Generators produce a huge amount of heat, meaning the interior components need to be constantly cooled to ensure there is no damage to the generator. The cheapest method of cooling is air cooling which requires an extraordinary amount of airflow and ducting equipment both adding to the amount of space needed and the overall cost. Liquid cooling is better but priced far higher.


  1. Noise

 Noise pollution from a generator is another problem, with many generators having to have additional canopies installed to reduce the ambient noise.

Even small generators of about 50kW can generate as much noise as city traffic (about 85dBA). Larger 1,500kW generators can emit around 105dBA which is as noisy as a jet aeroplane.

If the maximum noise allowed is 7dba @ 1 meter, this could be a cost in excess of £50,000+ to resolve, depending on the size and location of the generator.


  1. Servicing and maintenance

In theory, the Generator must be run on load every month meaning a service engineer must be on site for at least 2 hours.

Whereas a UPS or CSPS system only requires a battery discharge test every year. Generators also must be serviced annually with Oil filters and Oil being changed and coolants being tested and possibly changed.

At this time the Fuel is also sampled to ensure no degrading has taken place.


  1. Security

Unlike CPSS systems which are compact and easily fit inside standard rooms, generators are sometimes located outside of a building making them vulnerable to security risks. A security gate or cage is often constructed around the generator for safety and again adds more cost to the overall installation.


  1. Cost of diesel

With the cost of diesel reaching £2.00 a litre and more in some areas, the running costs are becoming prohibitive.

The quality of the fuel matters a lot, so the level of fuel regularly must be checked regularly, as running it low on diesel will damage the engine.


  1. Lead time

Delivery for typical Generators is being quoted at 36 plus weeks at the present time. A UPS supply and installation project is looking at a maximum 16 weeks delivery timescale.


Initial cost

The initial cost is often the sticking point for the surveyors. Servicing/maintenance and refuelling will fall under the Operational Expenditures (OpEx) which would take effect after project completion and consultants will occasionally not consider the ongoing cost to ensure the project comes in under budget, therefore mainly focusing on the Capital Expenditure (CapEx).

As standard, Power Control allow for all hardware, Batteries, Bypass Panels, DC installation (DC Cabling up to 5m) and Commissioning on all quotations meaning NO hidden costs are unexpectedly incurred.

*Equipment training, IST, FAT can be POA*


When compared to a UPS/CPSS

The key benefits of installing a CPSS would be the reduction in footprint depending on load, much cleaner energy as no emissions are being produced, substantially less noise pollution than a canopied generator and the ongoing maintenance would be less frequent and cheaper.

The initial cost would be similar to a generator depending on size. However, when adding up fuel, fuel delivery and ongoing maintenance costs associated with a generator the price of a UPS / CPSS is more attractive in this area.

Power Control has been specified for many projects across the country and prides itself on delivering critical power for a plethora of applications. All our CPSS systems are compliant with BS 9999 and EN 50171 regulations with a 120% overload capacity, IP rated acid proof enclosures, battery polarity reversal and 30 minute or 3 hour autonomy.

Please contact us for further assistance.