Commercial batteries store electricity and release it later for use on site or to sell back to the grid. They’re not the only way to reduce how much you import from the grid. By changing when you use your on-site equipment, you can reduce the amount of power you buy during the most expensive parts of the day.
In this article, we’ll explore the “alternative energy storage systems” you might already have and show how they can help lower utility bills. Then we cover how pairing them with a battery can help the whole site buy less grid power during the most expensive parts of the day.
The alternative energy storage systems you may already have on site
Below, find the assets and equipment that you may already have on site that you can save money on by changing when they draw power from the grid.
For each one, we’ve provided an example saving. To make the examples easy to compare, we’ve used a simple electricity price difference on a site with no solar or battery. We have assumed the site pays 30p/kWh during peak periods and 16p/kWh at cheaper times, giving a 14p/kWh difference for each kWh of electricity use avoided during the peak window.
Note: Using that assumption, every 10 kWh avoided during the peak period is worth about £1.40. We have not accounted for VAT, standing charges or any software and service costs. What you actually save will depend on your tariff, site load, equipment settings, and whether you have solar or battery storage.
1. Cold rooms, fridges and freezers
It’s worth checking your cold rooms, fridges and freezers first because they use a lot of electricity.
Cold rooms usually work within a temperature band rather than at one exact temperature. The saving comes from doing more cooling before the peak-rate period starts, bringing the room closer to the lower end of its approved range. The compressors then have less work to do when electricity is more expensive.
Accurate control is important here because you must still prioritise food safety rules. In England, Wales and Northern Ireland, chilled food must be kept at 8°C or below. Many operators set fridges lower than that, often around 5°C or below, to keep a safety margin.
Worked example
Take a 100,000 m³ cold store. Using the Cold Chain Federation benchmark of 10 kWh/m³/year, the refrigeration system would account for about 1,000,000 kWh a year.
If an operator shifted 1% of that use away from peak periods, that would put 10,000 kWh on the cheaper rate. At a 14p/kWh difference, this would be worth £1,400 before costs.
Another example is a freezer store with refrigeration use of 500,000 kWh a year. If 1% of that use avoided the peak rate, 5,000 kWh would be charged at the cheaper rate, worth about £700 before costs at 14p/kWh.
2. Hot water cylinders and thermal stores
Hot water cylinders and thermal stores hold heat in water. The saving opportunity is mainly on sites with an immersion heater, electric boiler, heat pump or electric top-ups, but not sites where most or all of the hot water comes from gas.
If your site has enough stored hot water to cover demand during peak-rate periods, you may be able to heat more of the water beforehand and use it later.
You need to heat the cylinder or thermal store before the peak-rate period starts, then reduce or delay electric heating when prices are higher. Be aware of hygiene rules when doing this. HSE guidance says hot water should be stored at 60°C or higher, and should reach 50°C at outlets within one minute, or 55°C in healthcare premises.
Worked example
To size up your site’s potential savings, use 1,000 litres as your benchmark. Heating 1,000 litres of water by 10°C takes about 11.6 kWh, based on the energy needed to raise 1kg of water by 1°C.
So, if one of your sites has a 3,000-litre thermal store, raising the temperature by 10°C before a peak-rate period would put about 35 kWh of heat into the water.
If you did this during the cheaper period rather than the peak window, you’d save £4.90 each time with a 14p/kWh difference between the cheap and peak rates. Do that 250 times a year and the total saving would be around £1,225 before costs.
Your system will need to use electricity later still to keep the water at the right temperature, but by doing more of the heating during the cheaper period, you reduce how much electric heating is needed when prices are highest.
3. Air conditioning, chillers and building temperature
Air conditioning and cooling costs can spike when the hottest and busiest parts of the day on a site overlap with the periods when electricity is at its most expensive. The savings here come from doing more of the cooling before the price rises and getting the system to use less power during peak-rate periods.
For example, on a hot day, you could cool the building slightly before the afternoon peak, while keeping rooms within agreed comfort limits. The building then starts the peak period at a lower temperature, so it takes longer for rooms to warm back up. That gives the cooling system more room to ease off while prices are highest.
Some buildings make this easier than others. If a site holds temperature well because of its insulation, layout or thermal mass, the cooling system has more room to ease back during peak-rate periods. If rooms warm up quickly, the savings may be small because comfort limits are reached too soon.
This isn’t the same as turning the cooling down and hoping your staff and visitors cope. Make sure that any pre-cooling or peak-period reduction keeps rooms within agreed comfort and ventilation limits, as recommended under HSE guidance.
Worked example
According to analysis from the BRE, median annual electricity use for office cooling is 40.5 kWh/m².
Let’s say one of your sites is a 5,000 m² air-conditioned office. This could mean annual cooling use of around 202,500 kWh at 40.5 kWh/m².
Start with a conservative model. If 5% of that cooling could happen before the peak-rate window instead of during it, 10,125 kWh would move out of the peak-rate period. At a 14p/kWh difference between the cheap and peak rates, that would be worth about £1,418 before costs over a year.
To do this, it’s best to have a building management system (BMS) that can change cooling settings automatically around tariff periods while keeping rooms within agreed comfort limits.
4. EV chargers and parked vehicles
Save money on EV chargers by moving charging to off-peak periods. The vehicles just need enough charge for the next shift. They don’t care whether the electricity was bought at 16p or 30p.
For example, in a delivery business, a shift may start at 7am and end at 6pm. When drivers leave work at 6pm, they plug in their vehicles. By restricting charging to cheaper overnight periods, you save money and the vehicles are still ready for the next shift.
This works best for companies with depot vehicles, fleet cars, staff cars and long-stay parking. It’s less easy to control for sites where charging demand is around the clock, like hotels and hospitals.
Worked example
Let’s say a delivery firm has 10 vehicles that each need 30 kWh before the next morning, totalling 300 kWH of charging.
If you moved that 300 kWh of charging out of the peak window, the saving would be £42 for that charging cycle at a 14p/kWh difference between the cheap and peak rates. Do that 250 times a year and the total saving would be around £10,500 before costs.”
What actions you can take today
| Asset | Who to speak to and what to ask | What to model, including costs | Approve action if... |
|---|---|---|---|
| Cold rooms, fridges and freezers | Speak to the facilities manager, refrigeration contractor or energy manager. Ask for annual refrigeration kWh, peak-rate use, approved temperature range and alarm limits. | Peak-rate refrigeration use that you could move onto the cheaper rate | Your stock will always stay within its approved temperature range |
| Hot water cylinders and thermal stores | Speak to the facilities manager, M&E contractor or maintenance team. Ask how much electricity hot water uses, when it heats, and when demand is highest. | Hot water heating that you could transfer to off-peak hours | Hot water will still be available when the site needs it. |
| Air conditioning, chillers and building temperature | Speak to the facilities manager, HVAC contractor or BMS provider. Ask for cooling use, peak periods, comfort limits and occupancy patterns. | Cooling use that could move out of peak-rate periods | Rooms and common areas will stay within agreed comfort and ventilation limits. |
| EV chargers and parked vehicles | Speak to the fleet manager, EV charging operator or facilities team. Ask when vehicles plug in, when they leave, and how much charge they need. | Charging that could happen during cheaper periods, | The vehicles you need will be ready on time |
Increase savings by pairing with a battery and/or solar
It’s possible to make meaningful savings by adjusting how and when you use your on-site electrical assets. However, on their own, those changes rarely add up to more than a small percentage of your overall bill.
The best way to increase the saving is to install a battery with control software that reacts to:
- Your import tariff: What you pay for electricity
- Site demand: How much electricity your building needs at given moments
- Battery charge level: How much electricity your battery is storing
- Your agreed import and export limits: How much power you can take and pass back to the grid
A battery takes the same timing idea further. It can store cheaper off-peak power and release it later when hot water, cooling, EV charging or other site demand would otherwise mean buying from the grid at a higher rate.
Add solar generation and the battery can also store surplus solar power, giving the site more electricity your supplier won’t bill you for. That stored solar can then be used later, instead of buying from the grid during the most expensive parts of the day.
GridVolt’s Energy Manager controls your on-site battery to maximise savings even further. It updates 96 times a day with the latest information, deciding when the battery should charge, discharge or hold its charge. This means the site can use cheaper stored electricity when buying from the grid would cost most.
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