Energy Baseline and Load Profile: Before You Claim Savings | Cobler
Blog
Before You Claim Savings: Baseline and Load Profile
An energy baseline records how much energy a building uses, when and why, before a change. Build one from twelve bills, half-hourly data, schedules and drivers such as weather, then state each saving as a range, worked through for an example office tower.
Tan Kok XinEnergy Management: The Economics of Saving Energy
Part 3 of 10 in Cobler's Energy Management: The Economics of Saving Energy course. New here?See the course page.
Part 2 valued three proposed measures for our example office tower at about RM158,065 a year, and those values are only as good as the kWh estimates behind them. Suppose a contractor tells you a new chiller schedule will cut your electricity use by 10%. The first question to ask is: 10% of what? An energy baseline answers it. It is a record of how much energy the building uses, when it uses it and why, before anything changes. Every saving in the rest of this course is measured against a baseline, so it has to be built before the project, not after.
This part builds the baseline for the tower, a fictional 20-storey building on the MV (medium voltage) non-domestic General tariff that we use throughout the course. It uses four kinds of evidence: twelve monthly bills, half-hourly meter data, the building's operating schedules, and the things that push consumption up and down, such as weather. By the end, we will know where the three measures come from, and each will have a range rather than a single number.
Start with twelve months of bills
The simplest baseline is a year of electricity bills. A single month is not enough, because consumption changes through the year. Hot months need more cooling, and months with public holidays or fewer working days need less. Twelve consecutive bills include every season and every holiday once.
Here are the tower's bills for October 2025 to September 2026. The numbers are illustrative.
FAQ
Frequently asked questions
Ask us about this topic
Something in this article you want to dig into — or a situation in your own building it doesn't quite cover? Send us your question. We don't run public comments; the team replies to you directly by email.
The year's total is 6,000,000 kWh. The busiest month, May, used 535,000 kWh. That is 65,000 kWh (about 14%) more than December, which used 470,000 kWh. Keep that swing in mind. If a project saves 2 or 3% of the building's electricity, the normal month-to-month swing is several times larger than the saving.
{{media:521}}
The tower's baseline year: consumption rises in the hottest months and falls in months with cooler weather, holidays or fewer days.
Check the bills against the meter data
Bills show one number a month. To see what happens inside a month, you need interval data: the energy recorded in every half hour. The maximum demand (MD) on the bill is the highest of these half-hourly readings in the month, as Maximum Demand: Why One Bad Half-Hour Costs So Much in the bill course explains. The data can come from the TNB (Tenaga Nasional Berhad) meter or from the building's own main meter. How electricity meters work explains how meters record it.
Before trusting interval data, add it up and compare it with the bills. The two should cover the same energy, so they should agree closely. For the tower, the half-hourly readings for the same twelve months add up to 5,944,000 kWh, which is 56,000 kWh (about 1%) less than the bills.
A gap like this has a cause, and it should be found before anyone uses the data. In the tower's case, a gateway outage in March 2026 lost three weekdays of readings. An average weekday uses about 18,600 kWh, so three missing days explain about 56,000 kWh. The team marks those days as missing and fills them from similar weekdays, and the two sources then agree.
Two other differences are normal:
Billing periods. A TNB bill runs from one meter reading date to the next, which may not match the calendar month. Compare totals over the same dates, or over the whole year.
Sub-meters. The meters on the chiller plant, risers and tenant floors will not add up exactly to the main meter, because of cable losses, meter accuracy and loads that no sub-meter covers. Why your sub-meter will never match TNB's meter explains the usual reasons. Treat the TNB meter as the reference for the bill, and use sub-meters to see where the energy goes.
Read the shape of a typical day
With the data checked, plot a day of half-hourly demand. This plot is called a load profile. The area under it is the day's energy in kWh, and its highest point is the demand in kW (Power vs Energy: What You Actually Pay For in the bill course explains the difference). For a baseline, we read it for what the building is doing at each hour.
{{media:522}}
The tower's MD day: a night base load of about 430 kW, a peak of 1,600 kW at 2:30pm, and cooling plant still running after 6pm.
Four features stand out:
The base load. Between midnight and 6am the tower still draws about 430 kW. This is the equipment that runs all the time, such as the server room, lifts on standby, car park lighting and fans, security systems and pumps. A base load is normal. A base load that creeps upwards month after month usually means equipment has been left on or is wearing out.
The morning rise. Demand climbs from about 6:30am as the cooling plant, the air handling units (AHUs) and the lights start, and reaches about 1,400 kW by late morning.
The afternoon peak. Demand is highest in the hottest part of the afternoon. On this day it reached 1,600 kW between 2:30pm and 3:00pm, which set the month's MD. Five half hours, from 1:30pm to 4:00pm, were above 1,500 kW.
The evening tail. After office hours, demand falls, but slowly. At 7:00pm the tower still draws 750 kW.
The whole month can be summarised in one number, the load factor: the average demand divided by the peak demand. For September, the average is 500,000 kWh spread over about 730 hours, and the load factor is 500,000 ÷ (1,600 × 730) ≈ 0.43. A low load factor means the building uses its peak capacity only for short periods.
The weekend matters too. On a Sunday the tower uses about 10,300 kWh, close to the base load all day. On a Saturday it uses about 12,400 kWh, because the plant runs in the morning for the few tenants who work then. An average weekday uses about 18,600 kWh.
Match the profile to how the building is run
A load profile shows what happens. To find out why, compare it with how the building is meant to run. For the tower, the facility team checks three sources: the office hours in the tenancy agreements (8am to 6pm, Monday to Friday), the BMS (building management system) schedules, and the sub-meters on the chiller plant.
This comparison turns up three findings:
The cooling plant runs two hours too long. The BMS log shows every AHU stopped by 6:00pm on normal weekdays, but the chiller plant is on an old schedule that keeps it running until 8:00pm. With no AHUs taking chilled water, those two hours cool almost nothing. The plant's sub-meter shows it drawing about 220 kW on average from 6pm to 8pm.
The condenser water pumps run at one speed. Each of the two duty pumps draws a steady 27.0 kW whenever it runs, on hot days and mild days alike. A pump fitted with a variable speed drive (VSD), which slows the motor when less flow is needed, could use less power at part load.
A small amount of load sets the peak. The five half hours above 1,500 kW exceed it by 10, 70, 100, 80 and 40 kW. If the BMS could hold off some non-urgent loads for those periods, the MD would fall. Candidates include the car park ventilation fans, the water transfer pumps that fill the roof tanks, and a small, temporary rise in the chilled water temperature.
These findings are where the three measures that Part 2 valued come from. We call them M1, M2 and M3:
M1: stop the chiller plant at 6pm, with an after-hours request button for tenants who work late.
M2: fit VSDs to the two condenser water pumps.
M3: BMS demand limiting that holds off selected loads in the top half hours.
The twelve bills we started with did not change at random. A few factors, often called drivers, explain most of the movement. For an office building, the main ones are:
Working days. A weekday uses about 18,600 kWh and an average weekend day about 11,400 kWh. So each extra working day in a month adds roughly 7,000 kWh. A month with a long public holiday uses less for this reason alone.
Weather. Hotter weather means more cooling. One common way to measure how hot a month was is cooling degree days (CDD). For each day, take the day's average outdoor temperature and subtract a base temperature, here 24 °C; a day averaging 28.5 °C gives 4.5 CDD, and a day at or below 24 °C gives zero. Add up the days to get the month's CDD. April 2026 had 135 CDD. Comparing the tower's twelve months, after allowing for working days, gives a rough slope of about 600 kWh for each extra CDD. Twelve points are not many, so this slope is an estimate, not a precise law.
Occupancy. A new tenant, an empty floor or a new server room changes consumption for reasons that have nothing to do with any savings project. The facility team should record these changes with their dates.
Why does this matter? If next April is hotter than this April, the tower will use more energy even if a savings project works perfectly. Without the drivers, the extra cooling would hide the saving, or a cooler month would make a failed project look successful. Part 4 uses these drivers to adjust the baseline before comparing it with the months after the project.
State the saving as a range, not one number
Each of the three findings from the schedule check gives a saving estimate, and each estimate depends on numbers that vary. It is more honest to give a low, central and high value, and to say what each one assumes.
For the tower, the team uses 22 working days a month, or 264 a year. Saturday morning running is left unchanged by all three measures, so it is not counted in any saving.
M1. The plant's average draw from 6pm to 8pm was 220 kW over the year, but the monthly averages ranged from 180 to 260 kW. Some tenants will ask for cooling after 6pm, which the team allows for by taking 20 kW off. The central estimate is 200 kW for 2 hours on each working day: 2 × 200 × 264 = 105,600 kWh a year.
M2. VSDs on condenser water pumps are limited by the minimum water flow the chillers need, so the saving is modest. The team estimates each pump will average 19.0 kW instead of 27.0 kW during the 11 hours from 7am to 6pm when both run. Together, that is 16 kW less: 16 × 11 × 264 = 46,464 kWh a year. The range allows 12 to 20 kW.
M3. Holding off loads moves energy to other half hours rather than removing it, so the team counts no kWh saving. What it can lower is the MD. The half-hour data suggests about 100 kW off each month's MD, with a range of 60 to 120 kW.
Measure
What is estimated
Low
Central
High
M1 Plant stops at 6pm
kWh a year
79,200
105,600
132,000
M2 VSDs on condenser pumps
kWh a year
34,848
46,464
58,080
M3 Demand limiting
kW off each month's MD
60
100
120
Together, the central kWh savings are 105,600 + 46,464 = 152,064 kWh a year. That is about 2.5% of the tower's 6,000,000 kWh, or about 12,700 kWh a month, much smaller than the 65,000 kWh swing between May and December. This is why a saving must be measured against a baseline that allows for the drivers, not read off the bill.
The range also protects the business case. When Part 9 tests the project, it will use the low and high values to see whether the decision still holds.
What comes next: proving the saving
We now have a checked baseline, the drivers that move it, and three measures with a range for each. Once the measures are installed, someone will ask whether the savings really happened, and the bill alone cannot answer, because weather, working days and tenants change it too. The next part, How to Prove Energy Savings: A Simple M&V Plan, uses this baseline and its drivers to write the plan that will measure and verify each measure.
Check your understanding
The tower's half-hourly data for the year adds up to 5,944,000 kWh, but the twelve bills add up to 6,000,000 kWh. What should you do before using the data? Find the cause of the 56,000 kWh gap. Here it was three weekdays of missing readings in March, which at about 18,600 kWh a day explain the difference. Mark those days as missing, fill them from similar days, and check that the totals then agree. Also check that you compared the same dates, because bill periods may not match calendar months.
The chiller plant draws about 220 kW from 6pm to 8pm on working days, and the team allows 20 kW for tenants who ask for cooling after 6pm. With 264 working days, what is the central yearly saving from stopping the plant at 6pm? The net saving is 220 − 20 = 200 kW for 2 hours a day, so 2 × 200 × 264 = 105,600 kWh a year.
Recap: A baseline records how much energy a building uses, when and why, before a change. Start with twelve months of bills, then check them against half-hourly data and explain any gap. Read the load profile for the base load, the rise, the peak and the evening tail, and compare it with the building's schedules to find waste. Identify the drivers, mainly working days, weather (measured as cooling degree days) and occupancy, so later months can be compared fairly. Give each saving as a low, central and high estimate. For the tower, the three measures are stopping the plant at 6pm, VSDs on the condenser water pumps, and demand limiting.
Cobler builds CobiNeural, a platform that shows a facility team its building's energy, water and indoor air data as live numbers across the whole site. To see how your building performs, talk to us.
Tan Kok XinEnergy Management: The Economics of Saving Energy
