Use Home & Energy as a calculation hub
Home-energy questions are connected. An electricity tariff changes the running cost of an appliance, a heat pump and an electric car. A building's heat demand affects both heating-system energy use and annual cost. Water use creates a water bill, while heating that water creates a separate energy cost. The most useful approach is therefore to start with the quantity you know, calculate one result, and reuse that result in the next relevant tool.
Electricity bills, appliances and everyday loads
If you already know total household consumption, start with the Electricity Cost Calculator. It accepts known kWh or meter readings and separates variable energy cost from fixed charges. If you want to understand where that consumption comes from, move to the Appliance Electricity Cost Calculator, which converts watts and operating time into kWh and cost.
For a specific high-use appliance, the Tumble Dryer Electricity Cost Calculator adds cycles per week, annual energy use and a simple comparison with an alternative dryer. For transport electricity, use the EV Charging Cost Calculator; it distinguishes vehicle energy from grid energy and can mix home and public charging prices. These tools can share the same electricity price, which makes comparisons easier to keep internally consistent.
Heating, heat pumps and hot water
For a conventional heating-cost estimate, use the Heating Cost Calculator. It starts from useful heat demand and adjusts purchased energy for system efficiency. If the home uses a heat pump, continue with the Heat Pump Electricity Cost Calculator instead of forcing a heat pump into a simple 0–100% efficiency model. The heat-pump calculator uses SCOP/COP and can separate space heating, domestic hot water and auxiliary electricity.
Domestic hot water can also be analysed on its own with the Hot Water Heating Cost Calculator. This is useful when you know litres per person, cold-water temperature and target hot-water temperature and want to separate hot-water energy from the rest of the heating bill.
Choosing heat emitters and operating temperatures
Annual energy cost is only one part of a heating decision. A room still needs enough heat output at the temperatures the system actually uses. The Underfloor Heating vs Radiator Calculator compares floor output and radiator output for the same room. The accompanying Underfloor Heating vs Radiators guide explains when each emitter type is practical in new builds, renovations and low-temperature systems.
When radiator catalogue output must be corrected for different water temperatures, use the Radiator Output Correction Factors table. It explains ΔT, correction factors and reverse sizing, so the table is useful both as a quick reference and as a bridge between a room heat requirement and a radiator selection.
Water use and water-heating energy are different calculations
The Water Cost Calculator estimates the utility bill from water volume, wastewater rate and fixed charges. It does not calculate the energy needed to heat that water. For that second step, use the Hot Water Heating Cost Calculator. Keeping these two costs separate makes it easier to see whether a change reduces the water bill, the energy bill, or both.
Solar payback and electrification decisions
If you are considering rooftop PV, the Solar Payback Calculator estimates the annual value of self-consumed generation and exported electricity before calculating simple payback. Results from other tools can help you think about when solar generation may be most valuable: appliance use, EV charging and heat-pump electricity all contribute to household electrical demand, even though the solar calculator itself deliberately stays a simple payback model rather than a full hourly energy simulation.
Learn the concepts behind the calculator results
If terms such as useful heat, kW, kWh, flow temperature, return temperature or ΔT are unfamiliar, start with Home Heating Basics in the Numbivo Academy. It connects the ideas used across the heating calculators rather than treating each formula as an isolated task. For a practical decision about emitters, continue to the underfloor heating vs radiators guide; for quick technical lookup, use the radiator correction-factor table.
Useful calculation paths
A good internal path depends on the question you are trying to answer. For a heating-system comparison, begin with annual heating cost, then calculate heat-pump electricity use, and finally check whether underfloor heating or radiators can deliver the required output. For household electricity, begin with the whole-bill calculator, then investigate individual loads with the appliance calculator or the dedicated dryer calculator. For water, calculate the water and wastewater bill first and then estimate the energy cost of hot water.
The category therefore works best as a map rather than a single giant calculator. Use one tool for one clearly defined result, keep the assumptions consistent between related calculations, and move to the guide, table or Academy page when you need to understand why the result changes.