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How we reduced our energy consumption by 30% in less than 6 months

By James Allston Wednesday 08 July 2015

We moved into our new Bristol headquarters in December 2014 after a 3 month refurbishment project. The building is 12 years old and, on the face of it, fairly efficient. There is excellent use of building controls and energy efficient technology. But we quickly discovered that it was not as efficient as it seemed at first. 

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We faced a further challenge: as a rapidly growing company we were likely to outgrow our HQ within 3 years, ruling out nearly all hardware measures. But after 6 months of work and spending less than £20,000, we managed to reduce our energy bill by 30% - that’s a saving of around £120,000 p.a. with a payback of less than 2 months.

Step 1: Install an energy data management system

After surveying the vast market of Energy Data Management Systems, we settled on a cloud-based energy data management system from UK-based Enistic. Key to our selection criteria was the platforms drill-down and analytical functions. We wanted to be able to quickly identify opportunities and assess whether changes we were making were having an effect. We installed 39 sub-meters in the building allowing us to see a detailed breakdown of the energy consumption in the building but without spending a fortune and “over-measuring”. 

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Step 2: Look for the quick wins

With the energy data management system installed, we could start looking at where energy was being wasted in the building. See the example below where we found 24kW of electric heaters on 24/7 in the gym change rooms. Switching these off saved us £10,000 and made for much happier, less sweaty gym goers.

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Huge savings in the gym!

A night audit on the following weekend revealed that our central plant (our heating, ventilation and air-conditioning equipment) was also running 24/7, partly some because of poor control settings and some because of controls left “in hand” (a manual state). Turning the plant from in-hand to auto instantly saved us another £10,000. The night audit also revealed that 30% of people were leaving their PCs running overnight. 

Step 3: Automatically switch everything off!

The next step was to solve the issue of equipment being left running overnight. Our security team were asked to switch off all the projectors and TVs in meeting rooms. Control routines were added to the servers to centrally switch off all the PCs and printers once everyone had left the building. Time control was optimized on our hot water taps (Billis) and added to the water coolers. This only cost a few hundred pounds and saved us over £1,000 per annum.

Step 4: Correct the not-so-smart stuff

When we started looking at the water coolers, we realised something pretty unhelpful had happened during the refurbishment - zone temperature sensors had been positioned directly above the water coolers, registering the heat coming off the condensing elements and therefore calling for the air-conditioning system to turn on unnecessarily. We’re still fixing this problem so we’re still not entirely sure of the savings, but it’s likely to be big.

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Where not to position a zone temperature sensor!

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Temperature data from a sensor above a water cooler versus normal 

Step 5: Tune the building management system

With the help of The Green Consultancy (TGC) and controls specialist DEMMA we looked deeper into the plant running overnight. It turned out that the chiller and air handling scheduling had never been set up properly and was subsequently causing the entire building to be filled with chilled outside air every night. Not only was this a waste of electricity running the fans, pumps and chillers, but the boilers were having to run overtime to reheat the building the next morning. TGC and DEMMA also found that the heating and cooling for the building were set to 22 degrees, meaning they were fighting each other and running all day. Fixing those problems saved us the better part of £100,000 and reduced our gas consumption by nearly 50%.

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Lots of gas saved  

What’s next?

We’re not happy at 30%, we still see lots more we can do. Next we want to tune the lighting controls, which we estimate will save us at least £3,000 and optimising the supply air pressure to save up to £10,000 more. We’re also investigating fuel conditioning (by MagnaTech) for our boilers to reduce their consumption by another 10%. 


The fact of the matter is, there are heaps of energy savings you can make in a building with a bit of clever thinking and getting in the right experts at the right time. OVO is yet another example of just how much low hanging fruit there is in the built environment to save energy.

O​VO​ Energy Ltd, registered office 1 Rivergate Temple Quay Bristol, BS1 6ED, company no. 06890795 registered in England and Wales, VAT No. 100119879

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1Monthly cost - Representative monthly direct debit costs based on a non-economy-7, dual-fuel, medium user (3100 kWhs elec. and 12500 kWhs gas) paying in advance by direct debit, including online discount.  All rates correct as of 06/06/2017, but may go up or down.

2Weekly cost - Representative weekly costs based on a non-economy-7, dual-fuel, medium user (3100 kWhs elec. and 12500 kWhs gas).  All rates correct as of 06/06/2017, but may go up or down.

3Pay Monthly Savings claims: Saving based on the estimated annual cost of OVO Two year fixed tariff for a non-economy-7, dual-fuel, medium user (3100 kWhs elec. and 12500 kWhs gas) paying monthly in advance by direct debit, including online discount. Comparisons made against the average of the Big 6 standard variable tariffs with equivalent features. All rates correct as of 04/10/2017.“The Big 6” are British Gas, Scottish Power, SSE, Npower, E.ON and EDF.

4Pay As You Go Savings are based on the average estimated annual costs for new PAYG OVO customers quoted through the OVO website (based on household and/or consumption information provided by those customers), compared to their current supplier and tariff. Comparisons taken between 01/01/2016 and 11/10/16. Incl VAT. Actual savings may vary according to your current supplier or tariff, individual tariff options, household information, consumption and location. 

We include almost twice as much renewable electricity as the national average: At least 33% of electricity in all of our tariffs comes from renewable sources. The national average, according to Ofgem as at March 2014 was 16.7%. For more information please visit this page.

33% of your electricity comes from renewable sources: 33% renewable electricity as standard as of 1st April 2015. Renewable electricity is generated from wind, solar, geothermal, wave, tidal, hydro, biomass, landfill gas, sewage treatment plant gas and biogas.

3% interest: Calculated at 3% per year for customers paying by advance direct debit.  The OVO Interest Reward is paid monthly based on   number of days in credit and the amount left in your account after you’ve paid your bill,  and the credit balance on which you can earn the OVO Interest Reward is capped. Terms apply:

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94% of surveyed customers would recommend us: OVO conducted a survey of their customers in between 1st January 2016 and 15th April 2016. Out of 15,312 customers who responded, over 94% rated OVO 6+ when asked 'how likely would you be to recommend us to a friend and family, on a scale of 1 to 10.

Britain's top rated energy provider: Britain's top rated energy provider in the Which? 2015 satisfaction survey. Survey conducted in October 2015. Awarded in January 2016.

uSwitch's Energy Supplier of the Year: OVO energy was voted and awarded  'Energy Supplier of the year' and best for: Overall Customer Satisfaction, Most Likely to be Recommended, Value for Money, Best Deal for You, Customer Service, Billing Services, Energy Efficiency, Meter Services, Online Services, Green Services and Transfer Process. OVO Energy scored a 96% customer satisfaction score.

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