Energy ToolsetHome Energy & Solar
Size solar panels, batteries, generators, furnaces and air conditioners, and estimate energy costs and savings.
AC BTU Calculator
Find the right air conditioner size in BTU for a room using the ENERGY STAR sizing chart, adjusted for ceiling height, sun exposure, occupants and kitchens.
Appliance Energy Hog Detector
List your appliances and how you use them, and an AI model in your browser flags likely energy hogs from age and run time. Free, private, no signup.
Attic Insulation Calculator
Work out how much R-value, depth and how many bags of blown-in cellulose, blown fiberglass or batts you need to bring your attic up to ENERGY STAR recommendations for your climate zone.
Battery Backup Use Case Classifier
Describe why you want a home battery and a text model in your browser matches it to a use case like outage backup or solar storage. Nothing is uploaded.
Battery Runtime Calculator
Estimate how long a battery, portable power station or UPS will run a load, using capacity, usable depth of discharge, inverter efficiency and an optional Peukert correction for lead-acid batteries.
Blower Door ACH50 & Natural Air Changes Calculator
Turns a blower door CFM50 reading into ACH50, estimates natural air changes per hour, compares ACH50 with the 2021 IECC limit for your climate zone, and gives the ASHRAE 62.2 total ventilation rate. For homeowners, energy auditors and builders.
Box Fill Calculator
Size electrical boxes to NEC 314.16 by counting conductors, devices, clamps, fittings and grounds. Compare the required cubic inches with a standard metal box or a marked volume and see how much room is left.
Ceiling Fan Size Calculator
Recommends a blade span for your room size, an estimated downrod length for your ceiling height, ENERGY STAR airflow and efficiency targets, and the yearly running cost of the fan. For anyone choosing a ceiling fan.
CFM Calculator
Calculate required airflow in cubic feet per minute from room volume and air changes per hour, or from a heating/cooling load and temperature difference. Includes the ASHRAE 62.2 whole-house ventilation rate and the 400 CFM per ton rule of thumb.
Conduit Fill Calculator
Check NEC conduit fill for EMT, RMC, IMC, PVC and flexible metal conduit using Chapter 9 conductor and raceway areas. Mix wire sizes and insulation types, see pass or fail, and find the smallest trade size that works.
Demand Charge Explainer
Paste the demand charge from your bill and an AI model in your browser explains what set the peak and how to lower it. Free, private, no signup.
Duct Size Calculator: Trunk and Branch Sizes from Your AC or Furnace
Already picked a 3-ton AC or an 80,000 BTU furnace? Enter it and get the round and rectangular duct size for the trunk and each branch, with velocity and noise flags.
Energy Label Photo Reader Preview
Checks an energy label photo's file type and size in your browser. It does not read the label numbers. No AI model runs; nothing is uploaded.
EV Charging Cost Calculator
Calculate the cost of charging an electric vehicle based on distance and electricity rates.
EV Charging Session Labeler
Paste an EV charging note and a text model in your browser labels it home, workplace, Level 2, DC fast or failed session. Free, private, no signup.
EV vs Gas Car Calculator
Compare ev vs gas car side by side. Make an informed decision with our free comparison tool.
Firewood Cord Calculator (Stack Size, Price & Heat Value)
Measures a firewood stack in cubic feet and cords, shows what you paid per full cord, and estimates heat content by species along with cost per million BTU. You can compare against your own electricity, propane and natural gas prices.
Furnace Size Calculator
Estimate the furnace BTU size for your home from square footage, climate zone, insulation, ceiling height and AFUE efficiency.
Generator Noise Note Classifier
Paste a generator note and an AI model in your browser lists noise readings and distances and rates how likely it bothers neighbors. Nothing is uploaded.
Generator Size Calculator
Add up running and starting watts for the appliances you need during an outage and get a recommended generator size with a safety buffer.
Heating Load Calculator (Design Heat Loss)
Estimate a building's design heat loss in watts and kilowatts from floor area, ceiling height, U-values for walls, roof, windows and floor, window share, air changes per hour and indoor and outdoor design temperatures.
Home Electrical Load & Service Size Calculator (NEC 220.82)
Applies the NEC 220.82 optional method to a single-family home to estimate service load in amps, pick the next standard service size, and show headroom for an EV charger or heat pump. For homeowners and contractors planning an upgrade.
Home Energy Savings Calculator
Estimate what solar panels, a home battery and a heat pump would save on your electric and gas bills using your own energy rates, sun region and incentives, then see the break-even year and 25-year net savings.
Home Load Audit Note Parser
Paste an appliance list or load audit and an AI model in your browser lists each load, rating and panel size for a load calculator. Nothing is uploaded.
kWh Cost Calculator
Calculate electricity cost from kWh, cost per kWh, appliance watts, daily runtime, fixed fees, and billing period.
Multi-Zone Mini Split Sizing Calculator
Estimates the cooling load of up to five rooms, rounds each to a standard ductless head (9k, 12k, 18k or 24k BTU/h), and suggests a multi-zone outdoor unit. For homeowners comparing quotes before asking an installer for a Manual J.
PC Power Supply Calculator
Add up your CPU, graphics card, drives, fans and peripherals to estimate peak system draw, the PSU wattage you should buy with headroom for GPU transient spikes, and what the PC costs to run each year.
Refrigerator Wattage Calculator
Turn the kWh per year on a refrigerator or freezer EnergyGuide label into average watts, compressor running and starting watts, daily to yearly energy cost, and the generator or inverter size it needs.
SEER Savings Calculator
Estimate how much electricity and money a higher-SEER2 air conditioner saves compared with your old SEER or SEER2 unit, with simple payback and 15-year savings. Old SEER ratings are converted to SEER2 so both systems are compared on the same basis.
Server Rack Power & Cooling Calculator
Totals the power of every device in a rack, shows amps per phase, how many circuits the 80% continuous rule requires, heat in BTU/h and tons of cooling, and a yearly electricity cost with PUE applied. For IT staff and small server room owners.
Solar Battery Size Calculator
Size a solar battery bank in kWh and amp-hours from daily energy use, days of autonomy, depth of discharge, inverter efficiency and battery temperature.
Solar Bill Before After Checker
Compare bills from before and after solar: an AI model in your browser lines up usage, export and credits as written. Private. Not financial advice.
Solar Panel Output Calculator
Estimate how many kWh your solar panels will produce per day, month and year from panel wattage, peak sun hours, system losses and roof orientation.
Solar Panel ROI Calculator
Enter what a solar installation costs and how much it should cut your monthly electric bill to see the payback period and net savings over 25 years. The federal 30% residential clean energy credit is applied only to systems placed in service in 2025 or earlier.
Solar Proposal Risk Checker
Paste solar quote or lease terms and an AI model in your browser lists price, warranty and clauses to question. Private. Not financial advice.
Solar Revenue Calculator
Multiply system size in kW by annual peak sun hours to estimate yearly production, then by your feed-in tariff or electricity rate to estimate revenue and the years needed to recover the installation cost.
Solar Sizing Calculator
Calculate the optimal solar panel size for your home or business based on energy consumption and sunlight availability.
Spray Foam Insulation Calculator (Board Feet & Kits)
Converts a target R-value and area into inches of spray foam, board feet with waste, the number of kits to buy and the material cost, and compares open cell with closed cell. For DIY buyers and contractors pricing a job.
Utility Rate Plan Summarizer
Paste a utility rate plan and an AI model in your browser lists peak hours, prices, demand charges and fees in plain English. Free, private, no signup.
Voltage Drop Calculator
Calculate voltage drop in volts and percent for DC, single-phase and three-phase circuits from wire size, material, current and one-way length. Checks the result against the NEC 3% and 5% guidance and finds the smallest wire that stays under 3%.
Wire Size Calculator
Find the smallest copper or aluminum wire that meets both NEC Table 310.16 ampacity at 75°C and your voltage-drop target, with an option for the 125% continuous-load rule. Shows whether ampacity or voltage drop sets the size.