12 BMS energy savings that actually work

If you’re looking to cut a building’s energy bill, the BMS is usually the cheapest place to start. Most of the savings don’t need new plant. They come from making the existing system do what it was designed to do, and from undoing years of quick fixes.

Here are twelve changes that reliably pay back, roughly in order of how easy they are.

1. Make the schedules match reality

Check every time schedule against how the building is actually used now. Occupancy patterns change, tenants move, hybrid working shifts the busy days, and the schedules often stay exactly as they were set years ago. Plant running two hours a day longer than it needs to adds up quickly.

2. Clear out the overrides

Go through every point that’s in hand, overridden or forced to a value, and find out why. A lot of them were set during a repair and never put back. A pump in “hand” runs 24 hours a day, every day.

3. Turn optimum start back on

If the heating starts at a fixed early time “to be safe”, let optimum start work it out instead. On mild days it’ll start much later. There’s more in how a BMS runs heating plant.

4. Fix the setpoints and add dead bands

Look at space setpoints, and add limits so occupants can only adjust them within a sensible range. Make sure there’s a proper dead band between heating and cooling, often a couple of degrees, so the same space isn’t heated and cooled back and forth.

5. Stop heating and cooling fighting

Find anywhere heating and cooling run at the same time: AHUs with overlapping sequences, fan coils fighting perimeter heating, or VRF cooling rooms that radiators are heating. Trending heating and cooling outputs side by side makes it obvious.

6. Add plant inhibits

Simple rules that stop plant running when it isn’t needed:

• no space heating above a set outside temperature
• no mechanical cooling below one
• boilers and chillers only enabled when something is actually calling for them

These are cheap to add and often missing.

7. Weather-compensate the heating

Flow temperatures should fall as the weather warms. Fixed high flow temperatures waste heat and stop condensing boilers condensing. With heat pumps, the effect on efficiency is even bigger.

8. Slow the fans down

Fans on VSDs are often left at a fixed speed set during commissioning. Look at static pressure setpoint reset on VAV systems, CO₂-based demand control in meeting rooms and large spaces, and simply reducing speeds where the design allows. Fan power rises very steeply with speed, so even modest reductions save a lot.

9. Get the pumps on proper DP control

Variable speed pumps should be controlled from a differential pressure sensor out near the index circuit, ideally with the setpoint reset as demand falls. A pump controlled across itself, or left at fixed speed, wastes most of what the VSD could save.

10. Raise the chilled water temperature when you can

Resetting chilled water flow temperature upwards at part load improves chiller efficiency, provided humidity isn’t a problem. See chiller plant control.

11. Make sure heat recovery works

Heat recovery that’s bypassed, stuck or running at the wrong times quietly costs money all year. Check that bypass dampers, wheel motors and run-around pumps do what the strategy says, and that summer and winter modes switch properly.

12. Use the meters to find out-of-hours waste

If the site has electricity and gas meters on the BMS, look at the night-time and weekend consumption. The baseload, meaning the energy used when the building is empty, is often surprisingly high, and every kilowatt of it runs 24/7. Comparing a typical weekday profile with a Sunday profile is a quick way to spot plant that’s running when it shouldn’t be.

For heating, comparing gas use against heating degree days over a few weeks shows whether consumption tracks the weather. If it doesn’t, something isn’t being controlled properly.

Make the savings stick

Savings fade if nobody’s watching. Set alarms or reports for:

• plant running outside its schedule
• points left overridden for more than a few days
• simultaneous heating and cooling
• out-of-hours baseload creeping up

A short monthly review of those reports does more than a one-off optimisation project that nobody follows up.

A word on priorities

Before changing anything, check it doesn’t affect safety or compliance. In particular, don’t touch hot water temperatures without the site’s Legionella arrangements in mind; see hot water and Legionella. And make sure frost protection always wins over any energy-saving rule.