Energy Tariff Calculator (UK): estimate your bill & compare
Use our UK energy tariff calculator to estimate what you’d pay on different tariff types (fixed, variable, EV/time-of-use) and see what to check before you switch.
- Works with credit, prepayment and Economy 7 / smart meters
- Compares unit rates (kWh) + standing charges (per day) — not just headline prices
- Transparent assumptions, examples with numbers, and common pitfalls to avoid
Estimates are based on the details you enter and available tariffs. Rates and eligibility vary by region, meter type and payment method.
Fast answer: what an energy tariff calculator does
A UK energy tariff calculator estimates your annual (or monthly) energy cost by multiplying your expected usage (kWh) by the unit rate, then adding the standing charge for each day of the year. It’s the quickest way to compare tariffs fairly — especially when one tariff has a lower unit rate but a higher standing charge (or vice versa).
Important: your final bill can differ from an estimate due to meter reads, seasonal usage, price changes on variable tariffs, government support, and regional rate differences. Always check the supplier’s tariff information label/terms before switching.
Key inputs that change your result
- Postcode region (rates vary across Great Britain)
- Payment method (direct debit vs receipt of bill vs prepayment)
- Meter type (single-rate, Economy 7, smart/time-of-use)
What “best tariff” usually means
- Lowest estimated total cost for your usage pattern
- Tariff type that fits your risk preference (fixed vs variable)
- Eligibility you actually meet (meter, smart requirements, EV, etc.)
What to check before switching
- Exit fees and end date on your current tariff
- Standing charge and unit rates (electricity and gas)
- Switch timing and whether you need a meter change
Simple formula (annual estimate): (Usage in kWh × unit rate) + (standing charge × 365)
If you don’t know your kWh: use your last 12 months’ bills, your online account, or your smart meter/IHD history.
Energy tariff calculator: enter details to estimate costs
To generate a meaningful estimate, we ask for a few details that affect UK energy pricing: postcode (region), meter setup, payment method, and your typical annual usage. If you only know monthly spend, it’s still worth switching to kWh for accuracy.
Tip: If you have an Economy 7 meter, split your electricity usage into day and night kWh if you can. If you can’t, use your annual total and note that the estimate may be less precise.
What you’ll need (and where to find it)
Annual electricity usage (kWh)
Look for “kWh used” on your latest bill/statement, or download the last 12 months from your supplier account.
Annual gas usage (kWh)
Gas bills sometimes show m³ and kWh. If you only see m³, your supplier converts it — your account usually shows the kWh total.
Your postcode
UK energy rates vary by distribution region. Your postcode ensures you’re comparing like-for-like for your area.
Meter type & payment method
Single-rate vs Economy 7 vs smart/time-of-use, plus direct debit, pay on receipt, or prepay.
Two realistic examples (with numbers)
Scenario A: All-electric flat (no gas)
- Assumed usage
- 2,200 kWh electricity/year
- Tariff A rates (example)
- Unit 26p/kWh, standing charge 55p/day
- Estimated annual cost
- (2,200×£0.26) + (365×£0.55) = £572 + £200.75 ˜ £772.75/year
- Estimated monthly equivalent
- £772.75 ÷ 12 ˜ £64.40/month
Example rates are illustrative only. Actual rates vary by region, supplier, payment method and meter type.
Scenario B: Typical dual-fuel household (gas + electric)
- Assumed usage
- 3,100 kWh electricity/year + 12,000 kWh gas/year
- Tariff B rates (example)
- Elec: 25p/kWh + 50p/day. Gas: 6.5p/kWh + 30p/day
- Estimated annual cost
- Elec: (3,100×£0.25)+(365×£0.50)=£775+£182.50=£957.50
Gas: (12,000×£0.065)+(365×£0.30)=£780+£109.50=£889.50
Total ˜ £1,847/year - What the calculator helps with
- Seeing whether a slightly higher unit rate is offset by a lower standing charge (or vice versa) for your usage.
Illustrative only. If you’re on Economy 7 or a time-of-use tariff, split usage by day/night/off-peak where possible.
Get a tailored quote (whole-of-market comparison)
Share a few details and we’ll show estimated costs based on available tariffs for your postcode, meter type and payment method.
Compare UK tariff types (what they mean in practice)
Tariff names can sound similar, but the trade-offs are different. This table focuses on what typically matters most: price certainty, who it suits, and key watch-outs.
| Tariff type | How pricing works | Often suits | Watch-outs |
|---|---|---|---|
| Fixed | Unit rates and standing charges are set for a term (e.g., 12–24 months). | People who want budget stability. | May have exit fees. If market prices fall, you may not benefit until the term ends. |
| Variable (standard/rolling) | Rates can change (often with notice). In GB, SVTs are typically influenced by the Ofgem price cap. | Those who may switch again soon or don’t want a tie-in. | Less certainty. Your estimate can change during the year. |
| Time-of-use (smart) | Different rates at different times (e.g., off-peak vs peak). Requires a compatible smart meter in many cases. | Homes that can shift usage (laundry/dishwasher overnight), EV charging. | If you can’t shift usage, you may pay more. Check peak windows and standing charges. |
| Economy 7 | Cheaper night rate for ~7 hours, higher day rate. Good fit depends on your day/night split. | Storage heaters, overnight-heavy usage. | If most usage is daytime, Economy 7 can be worse than single-rate. |
| Prepayment (PAYG) | Rates and standing charges are tariff-based; you top up as you go. | Those who prefer pay-as-you-go, some renters, budgeting needs. | Tariff availability can be narrower; check options for smart PAYG vs key/card meters. |
Decision checklist: who this calculator is for (and who it isn’t)
This calculator will help if you…
- Know your annual kWh (or can access it from bills/account)
- Want to compare tariffs fairly using rates + standing charges
- Are considering fixed vs variable and want the trade-offs clearly
- Have a smart meter / EV and want to sanity-check time-of-use options
It may not be enough on its own if you…
- Only know your monthly direct debit (this can include debt/credit)
- Have a complex setup (multiple meters, heat pump tariff constraints)
- Need support for debt, affordability, or disconnection risk (see Citizens Advice)
- Are looking for business energy (this page is for home energy only)
Renter? In most cases you can switch supplier if you pay the energy bills and your tenancy allows it, but always check your contract and speak to your landlord/agent if you’re unsure.
Costs, exclusions & common pitfalls (UK-specific)
Most switching issues come from a few predictable places. Use these checks to avoid surprises.
Standing charge can outweigh savings
Low usage homes (e.g., small flats) may not benefit from a slightly cheaper unit rate if the standing charge is higher.
Exit fees & timing
Fixed tariffs may charge exit fees. Some suppliers allow penalty-free switching in the final window before the end date—check your terms.
Direct debit ? actual usage
Your monthly direct debit can include catching up debt or building credit. For best accuracy, compare using kWh, not £/month.
Economy 7: day/night split matters
If you don’t use enough electricity overnight, the higher day rate can increase your overall cost even if the night rate is cheap.
Prepayment availability & meter changes
Some tariffs require a smart meter or a specific prepayment setup. If a meter change is needed, appointments can affect timing.
Discounts, perks and bundles
Focus on the estimated total cost first. “Perks” can be helpful, but they don’t always outweigh higher rates.
If your circumstances are urgent
If you’re struggling to pay, at risk of disconnection, or need emergency credit, use specialist support. Citizens Advice explains your options and supplier obligations.
Energy tariff calculator FAQs
1) What’s the difference between unit rate and standing charge?
The unit rate is what you pay per kWh of energy you use. The standing charge is a daily fixed cost to cover things like network and metering costs. Your total bill is the combination of both.
2) Why does my postcode change the price?
Energy distribution charges vary by region across Great Britain. Suppliers price tariffs differently depending on your electricity (and gas) network area, so the same tariff name can have different rates in different postcodes.
3) Can I switch if I’m renting?
Often, yes—if you’re the bill payer. Some tenancy agreements ask you to inform the landlord/agent or keep the property on a suitable meter type. Check your tenancy terms and don’t change anything the landlord pays for.
4) I only know what I pay each month—can I still compare?
You can, but it’s less reliable. Monthly direct debit amounts can include building up credit for winter or paying back debt. For a fair comparison, use your annual kWh from bills or your supplier account.
5) Does a fixed tariff always save money?
No. A fixed tariff mainly offers price certainty. Whether it’s cheaper depends on your rates, standing charges, exit fees, and what happens to market prices during the fixed term.
6) How does the Ofgem price cap affect my estimate?
In Great Britain, the Ofgem price cap limits the rates suppliers can charge on standard variable tariffs (and some default tariffs), based on typical usage. It doesn’t cap your total bill and doesn’t apply the same way to all fixed or specialist tariffs.
7) Do I need a smart meter for time-of-use or EV tariffs?
Usually, yes—because the tariff needs half-hourly (or similar) readings. Some suppliers may accept certain meters or require a smart meter installation before or after you join.
8) Will switching interrupt my supply?
Normally, no. Switching supplier is an administrative change and your gas/electricity should stay on. If a meter exchange is required, it’s arranged as an appointment.
9) What if I’m in credit or debt with my current supplier?
Credits are usually refunded after your final bill. If you owe money, you’ll still need to pay it. With some prepayment debt arrangements, switching may be restricted—get advice if you’re unsure.
Trust, methodology & sources
How we assess tariffs and produce estimates
1) We use your inputs: postcode region, meter type (single-rate, Economy 7, smart/time-of-use, prepay), payment method, and your stated annual kWh for electricity and gas.
2) We compare tariff costs on the same basis: estimated annual cost = (kWh × unit rate) + (standing charge × 365). For multi-rate tariffs, we use the split you provide (where applicable).
3) We surface key constraints: likely eligibility (e.g., smart meter required), contract length, and whether exit fees may apply (where provided in tariff details).
4) We highlight limitations (so you can sanity-check results): estimates don’t predict future variable-rate changes; they don’t include unknown account adjustments (debt/credit), and they depend on the accuracy of your kWh input.
Editorial independence: We aim to explain tariffs clearly and help you choose based on your household’s needs. Availability, prices and terms can change; always review supplier terms and the tariff information before you switch.
Sources (UK)
Ready to compare tariffs using your real usage?
Get a tailored estimate for your postcode, meter type and payment method. It’s the easiest way to see whether a fixed, variable or time-of-use tariff fits your household.
Estimates are indicative and based on entered usage and tariff details available at the time of comparison. Always confirm rates, fees and eligibility before switching.
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