Costs
Battery storage costs
There is no honest list price for a site battery project, because the cost depends on the equipment, the duration, the delivery and the supply route. What we can give you is the full list of what to compare, and the arithmetic to do it with your own figures.
- Compare total cost, not fuel alone.
- One-off delivery and set-up costs decide short projects.
- The comparison can come out against the battery. It should say so.
What makes up the cost
A site battery project has more cost lines than a generator hire. A fair comparison lists all of them for both arrangements.
| Cost | What to ask |
|---|---|
| Battery hire or purchase | Rate, minimum term, what is included |
| Generator hire | Whether a smaller set can be used, and the new rate |
| Fuel | Litres at the generator’s real load, not its rated consumption |
| Electricity | kWh drawn from the grid for charging, at your tariff |
| Delivery and collection | Transport for a unit weighing several tonnes |
| Lifting and positioning | Crane or other lifting, and ground preparation |
| Installation and commissioning | Connection, controls set-up and testing |
| Distribution equipment | Cables, connectors and any additional switchgear |
| Maintenance and monitoring | Servicing, remote monitoring and any software charges |
| Reserve or backup | Any standby supply the project requires |
For a purchase, add financing, the unit’s value at the end of the project, warranty limits and how much use it will actually get. See buy or hire.
Compare weekly running costs
Enter your own figures below. The starting values are an illustration only: a generator burning 1,200 litres a week replaced by a battery with a smaller generator burning 450 litres.
Weekly cost comparison
The starting figures are illustrative planning inputs, not quoted prices. Replace them with your own. The result uses only what you enter.
Result from your inputs
Not included: financing, residual value, distribution equipment, standby or backup requirements, and emissions. Compare against a correctly sized generator as well as the existing one, so savings from simple right-sizing are not credited to the battery. A proposal replaces these inputs with quoted costs.
The same arithmetic, worked through
With the illustrative starting values:
| Weekly cost | Existing diesel | Battery + smaller generator |
|---|---|---|
| Fuel | 1,200 L × £1.40 = £1,680 | 450 L × £1.40 = £630 |
| Generator hire | £400 | £250 |
| Battery hire | £0 | £700 |
| Maintenance | £80 | £40 |
| Weekly total | £2,160 | £1,620 |
The battery arrangement costs £540 less per week to run. Now add £1,000 of extra one-off delivery and set-up cost:
- Over four weeks: (£540 × 4) − £1,000 = £1,160 lower cost.
- Over two weeks: (£540 × 2) − £1,000 = £80 lower cost. Barely worth the change.
Change one input. If battery hire were £1,100 a week rather than £700, the weekly difference falls to £140:
- Over four weeks: (£140 × 4) − £1,000 = £440 higher cost.
Same site, same fuel saving, opposite answer. Every figure in this example is invented for illustration. None is a quoted price.
Three mistakes that flatter a battery
Counting fuel only. Fuel saved is real, but it is not the net saving until hire, delivery and set-up are subtracted.
Assuming fuel falls in line with running hours. A generator that runs half the hours at a higher load does not burn half the fuel. Use measured consumption at realistic loads where you can.
Crediting the battery for right-sizing. If the existing generator is simply too big, a smaller generator alone would save money. Compare the battery arrangement against a correctly sized generator as well as the one on site.
What moves the result most
- Project length. One-off costs are spread over more weeks.
- How under-loaded the generator is today. The lighter the load, the more there is to save.
- Fuel price and delivered fuel cost. Including the cost of deliveries and storage.
- Whether a grid connection can do the charging. Grid electricity often costs less per kWh than generator output, and removes fuel logistics.
- The battery hire rate or purchase price. Confirmed in a proposal.
Costs that are not on an invoice
Some effects are real but hard to price: fewer refuelling visits and less fuel stored on site, fewer engine service intervals, quieter running in sensitive hours, and lower exhaust emissions where people work. Record them separately from the money comparison. They may decide a close call, but they should not be used to hide an unfavourable one.
Emissions deserve care. A battery discharging on site produces no exhaust there. If it was charged by a diesel generator, the fuel was still burned, in fewer and more efficient hours. If it was charged from the grid, the emissions depend on the grid supply.
Getting real numbers
A proposal replaces every illustrative figure on this page with a quoted one: the equipment and configuration, hire or purchase terms, delivery, commissioning and support, and who you contract with. The guide to what to include in a BESS quote lists what to ask for so that quotes can be compared like for like.
Questions buyers ask
How much does a site battery cost?
It depends on the unit, the configuration, whether you hire or buy, the project length, and delivery and commissioning at your location. We do not publish a price list because a figure without those details would mislead. A project-specific proposal sets out the costs.
Is a battery cheaper than a diesel generator?
Sometimes. It tends to be when a generator runs long hours at low load on a long project. It tends not to be on short hires, where one-off delivery and set-up costs outweigh the fuel saved. Use the comparison on this page with your own figures.
Why can the calculator show a loss?
Because that is a real outcome. If battery hire and one-off costs exceed the fuel and hire saved, the existing arrangement is cheaper, and you are better off knowing before you commit.
Are fuel savings the same as cost savings?
No. Fuel is one line. A fair comparison also includes hire or ownership of every item, electricity used for charging, delivery, installation, commissioning and maintenance.