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
Appliance Energy Hog Detector helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
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
Battery Backup Use Case Classifier helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
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.
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.
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
Demand Charge Explainer helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
Energy Label Photo Reader Preview
Energy Label Photo Reader Preview helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
EV Charging Cost Calculator
Calculate the cost of charging an electric vehicle based on distance and electricity rates.
EV Charging Session Labeler
EV Charging Session Labeler helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
EV vs Gas Car Calculator
Compare ev vs gas car side by side. Make an informed decision with our free comparison tool.
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
Generator Noise Note Classifier helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
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 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
Home Load Audit Note Parser helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
kWh Cost Calculator
Calculate electricity cost from kWh, cost per kWh, appliance watts, daily runtime, fixed fees, and billing period.
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.
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
Solar Bill Before After Checker helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
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
Solar Proposal Risk Checker helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
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.
Utility Rate Plan Summarizer
Utility Rate Plan Summarizer helps review energy and utilities inputs locally with private local analysis, browser-side previews, and optional cached model upgrades.
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.