Example result based on the prefilled values.
Electricity
NZ$696.00/yr
Gas
NZ$632.50/yr
Total
NZ$1,547.50/yr
Monthly
NZ$128.96
Continue your plan
Useful next calculations
When to use this calculator
- Before switching supplier, upgrading equipment, or comparing energy-saving changes.
- When you want to test different usage assumptions or price scenarios quickly.
- When you need a simple estimate before requesting installer or supplier quotes.
- When you are evaluating solar panels, a heat pump, or insulation and want to check the payback period before spending.
- When your tariff is about to change and you want to quickly model the impact on your annual energy bill.
A realistic New Zealand planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Electricity Per Year (kWh)
25 years
Electricity Rate (p/kWh)
5%
Gas Per Year (kWh)
25 years
Gas Rate (p/kWh)
5%
After entering these figures, review electricity, gas and total together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Electricity
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Gas
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Total
This is the headline outcome of the calculation, but it is most useful when read alongside the supporting metrics below it rather than in isolation. Try changing one input at a time and watching how this total moves to understand which driver has the biggest impact.
Monthly
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This combined energy bill calculator brings together your gas and electricity costs into a single annual and monthly estimate, reflecting the way most UK households receive and think about their energy expenditure. It applies the unit rates and standing charges you enter for each fuel separately, so it is important to enter figures from your actual tariff rather than national averages, as rates differ between suppliers, regions, and tariff types. The calculation assumes consistent monthly usage, whereas in practice gas costs are heavily front-loaded into winter months. The tool is most useful for budgeting and for comparing the impact of switching tariffs or reducing consumption. It does not model direct debit smoothing, which many suppliers use to spread costs evenly across the year regardless of seasonal variation.
Common mistakes
- !Using an assumption that is not supported by a current local quote, bill, statement or official source.
- !Treating a generic estimate as a lender, provider, payroll or tax authority decision.
- !Mixing monthly and annual inputs without converting them consistently.
- !Forgetting location-specific taxes, fees, eligibility rules or payroll deductions where they apply.
- !Testing only one scenario instead of checking how a cautious assumption changes the result.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.
- Use the result to prepare better questions for a lender, provider, adviser or employer rather than treating it as a final answer.
Frequently asked
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