{"success":true,"version":"v1","request":{"tool":"list_calculators","category":"energy"},"result":{"entity_type":"calculator_list","status":"completed","count":12,"calculators":[{"calculator_id":"hvac-btu-sizing","entity_type":"calculator","name":"HVAC BTU Sizing Calculator","category":"energy","tool_name":"estimate_hvac_btu_sizing","description":"Estimates the cooling capacity (BTU/h, tons, kW) and heating output a room needs from floor area, ceiling height, climate, sun exposure, insulation, occupants and kitchen heat, using the 20 BTU/h per ft² rule of thumb with the ENERGY STAR room air conditioner adjustments.","use_when":"You need a quick size for a window, portable or split air conditioner or a room heater before shopping, or want to sanity-check a quoted unit size.","do_not_use_when":"You need a code-grade load calculation for a whole house (ACCA Manual J / ASHRAE methods account for windows, orientation and infiltration), or the heat flow through one wall (use heat-loss).","required_inputs":["floor_area"],"optional_inputs":["area_unit","ceiling_height_ft","climate","sun_exposure","occupants","kitchen","insulation"],"urls":{"html":"https://tttkmbb.com/energy/hvac-btu-sizing","markdown":"https://tttkmbb.com/energy/hvac-btu-sizing.md","schema":"https://tttkmbb.com/api/v1/calculators/hvac-btu-sizing","api":"https://tttkmbb.com/api/v1/calculate/hvac-btu-sizing"}},{"calculator_id":"heat-loss","entity_type":"calculator","name":"Heat Loss Calculator","category":"energy","tool_name":"calculate_heat_loss","description":"Computes the steady-state conductive heat loss through a building element from its area, its thermal transmittance (U-value, or an SI or imperial R-value) and the inside–outside temperature difference, with the daily and monthly energy and the cost at an electricity price.","use_when":"You want the heat flow through a specific wall, window, roof or floor at a given insulation level, or the energy an insulation upgrade would save.","do_not_use_when":"You need a room's equipment size (use hvac-btu-sizing) or ventilation losses (use air-changes-per-hour); the formula ignores air leakage, solar gain and thermal mass.","required_inputs":["area_m2","temperature_difference_k"],"optional_inputs":["u_value_w_m2k","r_value_si","r_value_imperial","hours_per_day","electricity_price_per_kwh"],"urls":{"html":"https://tttkmbb.com/energy/heat-loss","markdown":"https://tttkmbb.com/energy/heat-loss.md","schema":"https://tttkmbb.com/api/v1/calculators/heat-loss","api":"https://tttkmbb.com/api/v1/calculate/heat-loss"}},{"calculator_id":"room-lighting","entity_type":"calculator","name":"Room Lighting Calculator","category":"energy","tool_name":"calculate_room_lighting","description":"Computes the lumens a room needs from its floor area and a target illuminance (by room type or a custom lux value) divided by a light-loss factor, then the number of bulbs and the wattage at a given luminous efficacy.","use_when":"You are choosing how many LED bulbs or fixtures a room needs, or converting a lux requirement into lumens and watts.","do_not_use_when":"You need a photometric design with fixture spacing, beam angles or uniformity (use lighting-design software), or only the running cost of the lights (use electricity-cost).","required_inputs":["floor_area_m2","room_type"],"optional_inputs":["target_lux","lumens_per_bulb","light_loss_factor","luminous_efficacy_lm_per_w"],"urls":{"html":"https://tttkmbb.com/energy/room-lighting","markdown":"https://tttkmbb.com/energy/room-lighting.md","schema":"https://tttkmbb.com/api/v1/calculators/room-lighting","api":"https://tttkmbb.com/api/v1/calculate/room-lighting"}},{"calculator_id":"circuit-load","entity_type":"calculator","name":"Circuit Load Calculator","category":"energy","tool_name":"calculate_circuit_load","description":"Adds up the appliance wattages on one branch circuit, converts them to amperes at the given voltage and power factor, compares the load with the breaker rating (applying the NEC 80 % continuous-load limit when requested) and recommends the smallest standard breaker size that fits.","use_when":"You want to know whether a set of appliances will trip a breaker, how much capacity a circuit has left, or which standard breaker size a load needs.","do_not_use_when":"You need conductor sizing or voltage drop on a long run (use wire-voltage-drop), motor inrush or generator sizing (use generator-sizing), or a whole-service load calculation per NEC Article 220; local code and a licensed electrician decide the installed breaker.","required_inputs":["loads_w"],"optional_inputs":["voltage_v","breaker_amps","continuous_load","power_factor"],"urls":{"html":"https://tttkmbb.com/energy/circuit-load","markdown":"https://tttkmbb.com/energy/circuit-load.md","schema":"https://tttkmbb.com/api/v1/calculators/circuit-load","api":"https://tttkmbb.com/api/v1/calculate/circuit-load"}},{"calculator_id":"ev-charging-time","entity_type":"calculator","name":"EV Charging Time Calculator","category":"energy","tool_name":"estimate_ev_charging_time","description":"Estimates how long an electric vehicle takes to charge between two states of charge from its battery capacity, the charger power (capped by the onboard charger for AC charging) and the charging efficiency, plus the energy drawn from the grid and its cost.","use_when":"You want to know how long an EV needs on a home wallbox, a public AC post or a DC fast charger to reach a target charge, or what the session costs at a given electricity price.","do_not_use_when":"You need a battery's charge time from ampere-hours and charger current (use battery-charge-time) or the driving range the added energy gives (use ev-range-efficiency); DC fast charging above about 80 % tapers strongly and takes longer than this constant-power estimate.","required_inputs":["battery_capacity_kwh","charger_power_kw"],"optional_inputs":["start_percent","target_percent","max_onboard_charger_kw","charging_efficiency_percent","electricity_price_per_kwh"],"urls":{"html":"https://tttkmbb.com/energy/ev-charging-time","markdown":"https://tttkmbb.com/energy/ev-charging-time.md","schema":"https://tttkmbb.com/api/v1/calculators/ev-charging-time","api":"https://tttkmbb.com/api/v1/calculate/ev-charging-time"}},{"calculator_id":"ev-range-efficiency","entity_type":"calculator","name":"EV Range and Efficiency Calculator","category":"energy","tool_name":"calculate_ev_range_and_efficiency","description":"Converts an electric vehicle's energy consumption between Wh/km, kWh/100 km, Wh/mile, mi/kWh and km/kWh, computes the driving range from the battery capacity and usable share, and reports the EPA MPGe equivalent (33.7 kWh per US gallon of gasoline).","use_when":"You want an EV's range for a given consumption, or need to compare efficiency figures quoted in different units (European kWh/100 km, US mi/kWh or MPGe).","do_not_use_when":"You need charging time (use ev-charging-time) or running-cost comparison with a petrol car (use fuel-vs-ev-cost); real-world consumption varies with speed, temperature and heating by ±30 % or more.","required_inputs":["battery_capacity_kwh","efficiency_value","efficiency_unit"],"optional_inputs":["usable_percent"],"urls":{"html":"https://tttkmbb.com/energy/ev-range-efficiency","markdown":"https://tttkmbb.com/energy/ev-range-efficiency.md","schema":"https://tttkmbb.com/api/v1/calculators/ev-range-efficiency","api":"https://tttkmbb.com/api/v1/calculate/ev-range-efficiency"}},{"calculator_id":"fuel-vs-ev-cost","entity_type":"calculator","name":"Fuel vs EV Cost Calculator","category":"energy","tool_name":"compare_fuel_vs_ev_cost","description":"Compares the annual energy cost of a combustion car (L/100 km × fuel price) with an electric car (kWh/100 km × electricity price) over the same distance, and reports the savings, cost per km and the years needed to recover an EV price premium.","use_when":"You want to know how much an EV saves in fuel per year, the cost per kilometre of each car, or how long a higher purchase price takes to pay back from energy savings alone.","do_not_use_when":"You need total cost of ownership (insurance, maintenance, depreciation, taxes are not included), CO₂ comparison (use carbon-footprint-driving), or a single trip's fuel cost (use fuel-cost).","required_inputs":["annual_distance_km","fuel_consumption_l_per_100km","fuel_price_per_liter","ev_consumption_kwh_per_100km","electricity_price_per_kwh"],"optional_inputs":["ev_price_premium"],"urls":{"html":"https://tttkmbb.com/energy/fuel-vs-ev-cost","markdown":"https://tttkmbb.com/energy/fuel-vs-ev-cost.md","schema":"https://tttkmbb.com/api/v1/calculators/fuel-vs-ev-cost","api":"https://tttkmbb.com/api/v1/calculate/fuel-vs-ev-cost"}},{"calculator_id":"solar-payback","entity_type":"calculator","name":"Solar Payback Calculator","category":"energy","tool_name":"estimate_solar_payback","description":"Estimates the annual generation of a photovoltaic system from its size and specific yield, the first-year savings from self-consumed electricity and exported energy, the simple payback period, and a year-by-year table with panel degradation and electricity price escalation over the analysis period, including the levelised cost of the solar electricity.","use_when":"You want to judge a solar quote: how many years until the system has paid for itself, what it saves over its life, and what its electricity costs per kWh.","do_not_use_when":"You need the daily output of a panel array from irradiance (use solar-panel-output), a financed system with loan interest, or discounted cash-flow measures; results are estimates, not financial advice.","required_inputs":["system_size_kw","system_cost","electricity_price_per_kwh"],"optional_inputs":["annual_yield_kwh_per_kw","self_consumption_percent","feed_in_tariff_per_kwh","annual_degradation_percent","price_escalation_percent","analysis_years"],"urls":{"html":"https://tttkmbb.com/energy/solar-payback","markdown":"https://tttkmbb.com/energy/solar-payback.md","schema":"https://tttkmbb.com/api/v1/calculators/solar-payback","api":"https://tttkmbb.com/api/v1/calculate/solar-payback"}},{"calculator_id":"rainwater-harvesting","entity_type":"calculator","name":"Rainwater Harvesting Calculator","category":"energy","tool_name":"calculate_rainwater_harvesting","description":"Computes the rainwater a roof can collect per year from its horizontal area, the annual rainfall and a runoff coefficient, the litres captured per millimetre of rain, and, given a daily demand and tank size, the days of supply a full tank covers and the share of demand the yield meets.","use_when":"You are sizing a rain barrel or cistern, or want to know how much garden or toilet-flushing water a roof can supply.","do_not_use_when":"You need a month-by-month storage simulation with overflow and dry spells, or potable-water treatment sizing; the yield is an annual average and ignores first-flush diversion and evaporation beyond the coefficient.","required_inputs":["roof_area_m2","annual_rainfall_mm"],"optional_inputs":["runoff_coefficient","daily_usage_liters","tank_size_liters"],"urls":{"html":"https://tttkmbb.com/energy/rainwater-harvesting","markdown":"https://tttkmbb.com/energy/rainwater-harvesting.md","schema":"https://tttkmbb.com/api/v1/calculators/rainwater-harvesting","api":"https://tttkmbb.com/api/v1/calculate/rainwater-harvesting"}},{"calculator_id":"water-heater-energy","entity_type":"calculator","name":"Water Heating Energy Calculator","category":"energy","tool_name":"calculate_water_heating_energy","description":"Computes the energy needed to heat a volume of water by a given temperature rise (specific heat of water 4.186 kJ/(kg·K)) at a heater efficiency, the daily and annual energy and cost for repeated heating, and the heating time for a given heater power.","use_when":"You want the energy and cost of hot water for showers, a tank or a kettle, the annual cost of a water heater, or how long a heating element takes to heat a tank.","do_not_use_when":"You need standby losses of a storage tank or heat-pump water heater performance under varying conditions (enter its COP × 100 as the efficiency for a rough estimate), or non-water fluids (use specific-heat).","required_inputs":["volume_liters","temperature_rise_c"],"optional_inputs":["efficiency_percent","energy_price_per_kwh","heatings_per_day","heater_power_kw"],"urls":{"html":"https://tttkmbb.com/energy/water-heater-energy","markdown":"https://tttkmbb.com/energy/water-heater-energy.md","schema":"https://tttkmbb.com/api/v1/calculators/water-heater-energy","api":"https://tttkmbb.com/api/v1/calculate/water-heater-energy"}},{"calculator_id":"generator-sizing","entity_type":"calculator","name":"Generator Sizing Calculator","category":"energy","tool_name":"estimate_generator_size","description":"Estimates the generator size needed for a set of loads from the total running watts, the starting surge of the largest motor (peak = running total + starting − running of that motor), a safety margin and the power factor, giving the required kW (rounded up to 0.5 kW) and kVA plus the running current at 120 V and 230 V.","use_when":"You are choosing a portable or standby generator for a home, site or event and know the running and starting watts of the equipment.","do_not_use_when":"You need branch-circuit or breaker checks (use circuit-load), inverter or battery runtime (use battery-runtime), or three-phase and transfer-switch design; the sequential-start model assumes only one motor starts at a time.","required_inputs":["running_watts_total"],"optional_inputs":["largest_motor_running_watts","largest_motor_starting_watts","safety_margin_percent","power_factor"],"urls":{"html":"https://tttkmbb.com/energy/generator-sizing","markdown":"https://tttkmbb.com/energy/generator-sizing.md","schema":"https://tttkmbb.com/api/v1/calculators/generator-sizing","api":"https://tttkmbb.com/api/v1/calculate/generator-sizing"}},{"calculator_id":"air-changes-per-hour","entity_type":"calculator","name":"Air Changes per Hour Calculator","category":"energy","tool_name":"calculate_air_changes_per_hour","description":"Computes the air changes per hour of a room from its volume (or dimensions) and the ventilation airflow in m³/h, L/s or CFM, converts the airflow between units, and gives the airflow needed to reach a target ACH, with typical design values from ASHRAE standards.","use_when":"You are checking whether a fan, HRV/ERV, air purifier or HVAC supply provides enough air changes for a room, or sizing the airflow for a target ACH.","do_not_use_when":"You need outdoor-air rates per person or per floor area (ASHRAE 62.1 tables), infiltration from a blower-door test, or the heat lost with ventilation air (use heat-loss for conduction only).","required_inputs":["airflow_value","airflow_unit"],"optional_inputs":["room_volume_m3","room_length_m","room_width_m","room_height_m","target_ach"],"urls":{"html":"https://tttkmbb.com/energy/air-changes-per-hour","markdown":"https://tttkmbb.com/energy/air-changes-per-hour.md","schema":"https://tttkmbb.com/api/v1/calculators/air-changes-per-hour","api":"https://tttkmbb.com/api/v1/calculate/air-changes-per-hour"}}]},"timestamp":"2026-09-24T03:46:49Z","next_actions":[],"links":{"docs":"https://tttkmbb.com/calculators.md"}}