The Planning Method
- Calculate a baseline — one year, from your own meter readings, fuel use, mileage and flights.
- Identify the largest categories — in tonnes CO₂e, not in how often you think about them.
- Rank actions — by tonnes they could remove from your footprint, and by whether they are possible for you (cost, tenancy, location, timing).
- Model plausible reductions — recalculate each category with the changed input.
- Track progress — record the new readings over a year.
- Recalculate with the same method — same factors, same boundaries. Changing the factor set can move the result without any change in what you did.
Step 1 — Baseline
The Carbon Footprint calculator estimates home electricity, heating fuel, car and flights from your own inputs. Food and goods are not included; estimate them separately and label them as more uncertain. The carbon footprint guide explains boundaries, CO₂ versus CO₂e and how to avoid double counting — for example, EV charging that is already in your home electricity.
Why Percentages Depend on the Starting Point
A percentage only means something against a specific baseline. The same change removes the same tonnes from two households, but a different percentage: removing 2 t is 20% of a 10 t footprint and 40% of a 5 t footprint. A 50% cut can therefore be reachable with one or two large changes for one household and out of reach for another whose remaining emissions are mostly in categories it cannot control. Track absolute tonnes alongside the percentage.
Scenario Modelling — Worked Example
Illustrative household; every input is invented to show the method. Electricity, gas and car lines use UK Government 2025 factors (electricity 0.177 kg CO₂e/kWh, gas 0.18296 kg CO₂e/kWh gross CV, average petrol car 0.16272 and average battery-electric car 0.04047 kg CO₂e per vehicle-km). Flights, food and other are the household's own estimates, entered as round numbers.
Scenario B — replacing the gas boiler
| Category | Baseline input | Baseline t CO₂e | Scenario input | Scenario t CO₂e |
|---|---|---|---|---|
| Home electricity | 3,000 kWh | 0.53 | 3,000 kWh (+ heat pump below) | 0.53 |
| Heating | 12,000 kWh gas | 2.20 | A: 10,000 kWh gas after measured insulation | 1.83 |
| Car | 12,000 km petrol | 1.95 | 12,000 km battery-electric | 0.49 |
| Flights | own estimate | 1.50 | half the flights | 0.75 |
| Food | own estimate | 1.50 | unchanged | 1.50 |
| Other | own estimate | 1.50 | unchanged | 1.50 |
| Total | 9.18 | Scenario A | 6.60 (−28%) |
What the Scenario Shows
- Large categories dominate. In this example heating, the car and flights made up most of the baseline, so they offered most of the reduction. In a different household the order can be completely different.
- The result depends on factors. The EV and heat-pump lines depend on the electricity factor; on a grid with a higher factor they remove less. The Electricity CO₂ guide explains factor choice.
- The inputs are the uncertainty. Insulation savings, boiler efficiency and SCOP are placeholders here; use your own meter readings, a quote or a rating, and try a range.
- Reaching 50% may need categories the calculator does not model. That is a planning finding, not a failure.
Action Categories and Where to Model Them
- Electricity — use less (find loads with the DIY home energy audit), or change the factor through supply. Model with the Electricity CO₂ Calculator.
- Heating — reduce heat demand or change the heating system. The Heat Pump Savings calculator compares running costs; emissions follow from the fuel and electricity it reports.
- Driving — fewer km, sharing, or a different vehicle. See the transport carbon guide.
- Flights — fewer or shorter flights; the Flight vs Train CO₂ calculator compares a specific trip.
- Food — the food carbon guide shows how to estimate a change from quantities and lifecycle factors.
- Consumption — goods and services are usually estimated from spending and are the most uncertain line; treat changes there as rough.
No action has a fixed percentage saving: each depends on your baseline and inputs.
Tracking Progress
Record the same inputs each year — meter readings, fuel bought, odometer, flights — and run them through the same factor set. If you update to newer factors, recalculate the baseline with them too, so the change you see reflects what you did rather than a change in the dataset. The Carbon Footprint hub collects the tools; the methodology page lists the sources.