Base load is the minimum electricity a building uses at all times, overnight and at weekends as well as during the day. Each kilowatt of base load runs for 8,760 hours a year. That's 8,760 kWh, or about £2,190 at 25p/kWh. You can measure it from half-hourly data, find out what makes it up, and switch off anything that doesn't need to run.
How to measure it
The analyser takes every valid half-hourly reading, converts it to kW (the kWh reading divided by half an hour) and finds the level that demand stays above 95% of the time. This is called the 5th percentile, and it's what the analyser uses as the base load.
It doesn't use the single lowest reading, because one meter fault or power cut could set it and make the base load look lower than it really is. The analyser shows the lowest half hour alongside so you can compare.
What makes it up
- IT: servers, network equipment and phone systems
- Refrigeration: kitchen fridges, freezers, vending machines and water coolers
- Pumps and fans that run continuously
- Water heaters and boilers kept on standby
- Security systems, fire alarms and emergency lighting
- Equipment left on standby, or left running by mistake
How to reduce it
- Walk round the building at night or at a weekend and note everything that's switched on. It's often a surprise.
- Sort what you find into must run, could run less, and shouldn't be on.
- Fix the easy ones first, such as timers on water heaters and vending machines, switch-off routines and combining servers.
- Check the base load every month. A step up usually means new equipment has been installed or something has been left on. The analyser flags lasting changes like this.
Base load and solar
Base load runs through the day as well as the night, so it is the part of your demand that solar panels can supply most reliably. The analyser's Capacity tab estimates how much of a solar system's output your site would use itself at different sizes, from your own half-hourly readings, and can pass that figure to our sister site, the UK Solar Calculator, to work out costs and payback. The solar page explains how.
Working out the saving
Because base load runs every hour of the year, savings are easy to estimate: multiply the kilowatts you remove by 8,760 hours and by your unit rate. At 25p/kWh, 1 kW is worth about £2,190 a year, and switching off a 0.5 kW water heater that was left on all the time saves about £1,100.
Questions people ask
What is a typical base load?
It depends on the building. An office with a lot of IT, or a site with refrigeration, will have a much higher base load than a school. Compare each site with its own history, and with similar buildings in your estate.
Why is my base load higher at weekends than overnight on weekdays?
It shouldn't be. If it is, something is switching on at weekends, such as frost protection on the heating, a scheduled process or a booking. Check the weekend pattern on the heatmap.
How much does 1 kW of base load cost?
It runs 8,760 hours a year, so it uses 8,760 kWh. At 25p/kWh that's about £2,190 a year. Multiply 8,760 by your own rate to check.
