Solar & Energy Calculators
14 calculators14 free calculators for solar & energy homeowners.
Attic Insulation Bags
Count the bags of blown-in fiberglass or cellulose your attic needs, and the inches to add, from its size, what's already there and your climate zone.
Attic Insulation Cost
Estimate attic insulation cost by square footage and type — blown-in fiberglass, cellulose, or spray foam — with old-insulation removal, every material compared, and a payback estimate based on ENERGY STAR energy-savings data.
Generator Installation Cost
Installing a whole-home standby generator costs $6,000–$11,000 for most houses — up to $24,000 for big homes with long hookup runs. Price your size, hookup, and fuel, permits included.
Generator Size
Find the generator size you need in watts or kilowatts: pick essentials, comfort, or the whole house, say whether you're on a well, and get the portable class or standby size that covers both the running load and the starting surge, using the utility sizing worksheet and manufacturer wattage charts.
Heating Oil Usage
Turn your oil tank's float gauge into days: how many gallons a day your house burns this month by size and weather, when to order before you hit a quarter tank, when the tank runs dry, and what the month costs. Built on supplier burn rates per square foot and the real 240-gallon fill of a 275 tank.
Holiday Lights Electricity Cost
See what your Christmas lights add to the electric bill for the season, from the bulbs and the hours, and what the same display costs in the other kind of bulb.
Microinverter vs. String Inverter
See whether microinverters or power optimizers are worth the extra cost over a string inverter. Based on your roof's shading, this estimates the extra energy they recover, the yearly and lifetime savings, and the break-even on the premium.
Natural Gas Heating Cost
See what heating your home with natural gas costs in a winter month and over the whole season, from its size, your climate, furnace and gas price.
Propane Usage
Turn your propane gauge reading into days: how many gallons a day your house is using this month, when to order a refill before you hit the 30% mark, when the tank runs dry, and what the month costs. Built on supplier usage figures by home size, scaled for mild, typical, and cold-snap weather.
Solar Battery Storage
Calculate how much battery storage you need based on your solar generation, daily usage, and backup goals. Get an instant capacity estimate and installed cost range.
Solar Panel Output Estimator
Estimate how much electricity your solar panels will produce. Enter your system size, state, and efficiency to get daily, monthly, and annual kWh output instantly.
Solar Payback Period
Calculate your solar payback period in minutes. See exactly how many years until your panels pay for themselves based on cost and savings.
Solar vs. Grid Electricity Cost
Compare the total cost of going solar versus staying on the grid over time. Enter your bill, system cost, and rate increases to see lifetime savings and payback period.
Standby Generator Runtime Cost
Calculate what a whole-house standby generator costs to run per hour, per day, and across a 3-day outage — by size, fuel, and load. Natural gas vs. propane vs. diesel at current EIA fuel prices.
About Solar & Energy Calculators
Home energy decisions carry some of the longest payback periods and biggest dollar swings of any home investment — a solar array is a 25-year commitment measured in tens of thousands of dollars, a standby generator's fuel bill during one extended outage can exceed its annual maintenance, and the gap between an efficient and inefficient home shows up on every utility bill for as long as you own the house. These calculators exist to put real numbers on those decisions before you sign anything. The solar tools estimate system payback from your actual roof, rates, and local sun rather than a salesperson's best-case brochure, and the battery storage calculator weighs backup capability against its price honestly.
The generator calculators cover both directions of the cost question: what standby power costs to run per hour and per outage across natural gas, propane, and diesel, and how fuel choice changes the math. The comparison tools — solar versus grid power, inverter options, efficiency upgrades — are built to show the break-even point, because in energy the right answer is almost always a payback question, not a product question. Every calculator cites its sources, states its assumptions plainly, and separates what is measured from what is estimated, so you can sanity-check any quote against numbers that were not produced by the person selling the equipment.
Start with the calculator closest to the bill you are trying to shrink.