When should you switch business energy?

The timing of your business energy switch can be just as important as the deal you secure. Switch too late, and you risk being rolled onto expensive out-of-contract rates. Switch at the right moment, and you can lock in a competitive fixed deal before prices move against you. 

This guide explains how business energy contracts work, what a renewal window is, how to spot the signs that now is the right time to act, and more.

In this guide to switching business energy...

• Most businesses can start the switching process between one and six months before their contract end date, sometimes longer
• Missing your renewal window can trigger expensive rollover or deemed rates
• Wholesale market timing can affect how much you lock in over the long term
• Comparing early gives you a wider choice of suppliers and tariff types. The switching process can take as little as five working days for some businesses, and does not disrupt your supply

How business energy contracts work

Unlike domestic energy, business energy contracts are negotiated directly between your business and a supplier, or through a broker or comparison service. There are no "off-the-shelf" tariffs, and there is no price cap on business energy, which means the rate you pay depends entirely on the deal you agree to and when you agree to it.

Most small and medium-sized businesses choose fixed-rate contracts to lock in a unit rate and standing charge for gas and electricity over an agreed term. Fixed contracts typically run for one, two, or three years, but longer terms may be available. At the end of that term, your contract expires, but you need to act before it ends.

If you do nothing when a contract ends, your supplier will automatically move you onto its out-of-contract rates. These are almost always more expensive than the fixed-rate deal you were on, and unlike fixed contracts, they carry no price protection if the market moves.

Contract type	What it means for your business
Fixed-rate	Unit rate locked for the contract term. Greater budget certainty, protection from price rises
Variable-rate	Rate moves with the wholesale market. Can fall, but can also rise
Out-of-contract	Default rate when a fixed deal expires. The average customer saves 35% by signing a direct contract with our partners at Bionic versus going out of contract.
Deemed rate	Applied when a business moves into premises with no energy contract in place. Usually among the highest rates available

What is a renewal window?

A renewal window is the period before your contract end date during which you are allowed to give notice to switch suppliers or renegotiate your deal. Most business energy suppliers set a notice period of between 28 and 90 days, though some contracts specify up to 120 days, so check your contract for the exact terms.

The renewal window is important for two reasons. 

1. It's time to take action: if you miss it without notifying your supplier, many contracts automatically roll over into a new fixed term at the supplier’s standard rates. These are rarely competitive. 
2. It's an opportunity to compare other options: instead of just agreeing to your existing supplier's renewal offer, run a business energy comparison to see what else is on offer.

When to start comparing quotes

Aim to begin comparing at least three to six months before your contract end date. This gives you time to gather quotes from multiple suppliers, assess tariff options, and complete the switch before your current deal expires.

Notice period: what to look for in your contract The contract end date (sometimes called the ‘expiry date’ or ‘renewal date’) The notice period. This is the minimum number of days you must give before switching Any automatic rollover clause, which locks you into a new term if notice is not given in time Early termination charges, which apply if you try to leave before the contract ends If you’re unsure of your end date, contact your current supplier or check a recent bill. Your MPAN (electricity) or MPRN (gas) number will be on your bill and is needed to switch.

What are the risks of missing your renewal date?

Failing to act within your renewal window is a common, and often expensive, mistake made by small business owners. Here is what can happen if you don't sort out a new contract to start once your current one ends.

Rollover contracts

These aren't as common as they used to be, but still something to be aware of. Some suppliers amy include an automatic rollover clause in their contracts. If you don't give notice within the specified window, the contract automatically renews, usually for another 12 months at the supplier’s standard rate. You are then locked in for a further year, often at a significantly higher rate than you could have secured by switching.

Out-of-contract rates

If your contract expires without a rollover clause, you move onto the supplier’s out-of-contract rates. These are variable, unprotected, and expensive. Figures from our partners at Bionic show that, in 2026, average out-of-contract electricity rates for SMEs are running at around 38p per kWh, with a standing charge of £2.58 per day. For gas, out-of-contract rates average at 11p per kWh with a standing charge of £3.41 per day.

Deemed rates

Deemed rates are a separate category, applied when a business moves into new premises and has not yet agreed a contract with the energy supplier. They are typically among the most expensive rates available and, like out-of-contract rates, offer no price protection. You can exit a deemed contract at any time by giving 28 days’ notice, so if you find yourself on deemed rates, act immediately.

The cost of doing nothing Consider this as an example of how costly it can be to simply ignore your energy renewal. A small business using 10,000 kWh of electricity per year on out-of-contract rates of 38p/kWh would pay around £3,800 annually. The same business on a competitive fixed deal at 25p/kWh would pay £2,500 — a difference of £1,300 per year. Comparing and switching at the right time eliminates this unnecessary cost.

Fixed vs flexible timing strategy

It not only matters when you switch, but it also matters what type of contract you switch to. Whether a fixed or variable contract is right for your business depends partly on market conditions at the time you compare.

The case for fixing now

Fixed contracts are the default choice for most SMEs because they offer predictable costs and protection against future price rises. In 2026, there is an additional argument for locking in: network charges for businesses rose significantly from April 2026, with Transmission Network Use of System (TNUoS) charges increasing by over 60% year-on-year according to the National Energy System Operator (NESO). But these non-commodity costs can still be variable, so check with your supplier or broker before agreeing a contract.

The case for flexibility

Variable and flexible contracts can suit businesses with predictable, high-volume usage that have the in-house expertise to track market movements. For most SMEs, however, the risk of variable pricing outweighs the potential upside, particularly in a volatile market.

Forward buying and price hedging

Larger businesses with dedicated procurement resources may be able to access forward buying arrangements, locking in a price for energy to be delivered at a future date. This is less common for SMEs but increasingly available through specialist brokers. If your business uses more than 55,000 kWh of electricity or 200,000 kWh of gas per year, it is worth exploring bespoke procurement options.

How to switch business energy: step by step

Switching business energy suppliers doesn't need to be difficult. Instead of going it alone, get the help of an energy expert who can compare a range of quotes in one go and answer any questions. Remember, non-domestic energy contracts don't offer a cooling-off period, so you need to make sure you're completely happy with the terms before you sign.

Once you agree to a contract, the process is largely handled by your new supplier, and your energy supply will not be interrupted at any point.

Here's a simple step-by-step guide to switching:

1. Check your contract end date and notice period. Log in to your supplier’s account portal or call them to confirm your contract end date and the notice period required to switch. Remember, this can be months before your contract's end date.
2. Gather your billing information. You will need your MPAN number (electricity) and MPRN number (gas), both of which are printed on your energy bill. You will also need your estimated annual consumption in kWh, your business address, and basic company details.
3. Compare quotes from multiple suppliers. Use a comparison service to get a range of quotes at once. This will save you the time and hassle of individually ringing around numerous suppliers. Your existing supplier’s renewal offer is rarely the best available rate, even if it looks competitive. Comparing takes a few minutes and costs nothing.
4. Choose your tariff and confirm the switch. Once you have selected a deal, the new supplier manages the switching process. You do not need to contact your old supplier directly as the new supplier handles the notification. Our energy experts will also be on hand to support you through the switch.
5. Take meter readings on your switch date. Record meter readings on the day your new contract starts. Send these to both your old and new suppliers to ensure accurate final and opening bills.
6. Your supply continues uninterrupted. Your new contract will start when your current one ends, meaning you're not left with an expensive contract gap. Your gas and electricity supply will not be cut off or interrupted at any point during the process.

Signs you should switch now

Not sure whether the time is right? Here are the clearest signals that you should start comparing business energy deals today.

• Your contract ends within six months. Start comparing now to give yourself the best choice of supplier and tariff before your renewal window closes.
• You’ve received a renewal notice from your current supplier. Suppliers are required to notify you before your contract ends. A renewal letter is your signal to compare quotes before accepting their offer.
• You’re on out-of-contract or deemed rates. You can switch at any time with just 28 days’ notice. Every month on an unprotected rate is an unnecessary overspend.
• You haven’t reviewed your contract in over 12 months. The energy market moves quickly. A deal that was competitive a year ago may no longer be. Set a reminder to compare at least annually.
• Your business has changed significantly. If your premises, headcount, or operating hours have changed, your energy consumption profile may have shifted. A new comparison will ensure your tariff reflects your current needs.
• You’ve seen your bills increase without explanation. Rising bills on a fixed contract can signal that you’ve rolled over onto standard rates. Check your contract status before paying more.

Frequently asked questions on switching business energy

Still unsure about when to switch business energy suppliers? Check out the answers to our most frequently asked questions.

How far in advance can I switch business energy in the UK?

Most business energy suppliers allow you to give notice and arrange a new contract at any point during your notice period. This is typically 28 to 90 days before your contract end date. But you can begin comparing quotes and agree to a new deal earlier, often three to six months before your contract expires. If you do arrange a new contract, it'll start on the day your current contract ends. Check your existing contract for your specific notice period.

What happens if I miss my renewal window?

If you miss your renewal window, your supplier may roll your contract over into a new fixed term at their standard rates, or move you onto variable out-of-contract rates. Both outcomes are typically more expensive than a competitively sourced fixed deal. If this happens, check whether you are in a rollover contract with an exit date, or on rolling out-of-contract rates, which can be exited with 28 days’ notice.

Can I switch energy mid-contract?

Switching mid-contract is not usually possible on non-domestic energy contracts. The only exceptions are usually that your business has moved premises and a change of tenancy (CoT) transfers the responsibility for the energy supply to a new occupant.

How long does switching take for businesses?

Under the Ofgem Energy Switch Guarantee, a business energy switch should be completed within five working days of the agreed start date. You can often request a specific switch date to coincide with your contract end date. Your energy supply will not be interrupted during the switching process.

Do all suppliers have the same renewal periods?

No. Notice periods vary by supplier and are set out in your contract terms. They typically range from 28 days to 90 days, although some older contracts specify longer periods of up to 120 days. Always read your contract carefully and note the notice deadline in your calendar well in advance.

Is it cheaper to switch early or wait?

Switching early is almost always beneficial because it gives you more choice and time to compare. Waiting in the hope that prices will fall carries risk. Wholesale energy prices are unpredictable, and non-commodity charges such as network costs are generally rising regardless of wholesale movements. Comparing early costs nothing and protects you from being caught out by a missed renewal window.

Can I lock in future energy prices?

Yes. Fixed-rate business energy contracts lock in your unit rate for the contract term, protecting you from price increases during that period. Some larger businesses can also access forward purchasing arrangements, agreeing prices for energy to be supplied at a future date. For most SMEs, a standard fixed-rate contract secured at comparison is the most straightforward way to achieve price certainty.

Will switching disrupt my supply?

No. Switching business energy suppliers does not affect your physical energy supply. The gas and electricity entering your premises comes through the national grid and distribution network, regardless of which supplier you are contracted with. The switch is purely an administrative process. Under the Ofgem Energy Switch Guarantee, the switch is completed within five working days, and your supply continues uninterrupted throughout.