The Tools
Financial Tools for Sustainable Living and Personal Finance
Calculators for solar panels, EVs, heat pumps, and the personal finance fundamentals behind them. Real math, plain English.
Sustainable Finance
Solar, EVs, and Energy Upgrades
The financial math behind solar panels, EVs, heat pumps, and home energy upgrades.
Solar ROI Calculator
Model your system size, local electricity rates, and incentives to find your break-even and 25-year ROI.
Heat Pump vs Gas Furnace Calculator
Full cost comparison: heat pump vs gas furnace across climate zone, fuel prices, and IRA incentives.
Home Electrification Payback Calculator
Combined payback for all major gas-to-electric upgrades: heat pump, HPWH, induction range, dryer, EV charging, and solar. IRA credit stacking included.
EV Charging Cost Calculator
What it actually costs to charge an EV at home and at public stations, compared to a gas car.
Personal Finance
Investing, Debt, and Major Purchases
Calculators for investing, debt payoff, savings rate, and the big financial decisions.
Compound Interest Calculator
See how compound interest grows money over time with custom contributions, rate of return, and time horizon.
Cost of Waiting Calculator
The exact dollar cost of delaying an investment, with two scenarios that differ only in when you start.
Debt Payoff Calculator
Compare avalanche vs. snowball debt payoff side by side: payoff order, interest saved, and debt-free date.
FIRE Number Calculator
Calculate your early retirement target using the 4% rule, with adjustable withdrawal rate and projected date.
Savings Rate Calculator
Find your savings rate and see how many years each additional percentage point trims from your FIRE timeline.
Emergency Fund Calculator
Find out how much emergency fund you need (3, 4, 6, or 9 months) and a clear timeline to fully funded.
True Cost of Car Calculator
Compare gas, hybrid, and electric vehicles on full 5–10 year cost of ownership, not just the sticker price.
Retirement Readiness Planner
See whether you're on track, how far off you are, and what it would take to close the gap.
Net Worth Tracker
A clear snapshot of where you stand: assets, liabilities, and the number that matters.
Rent vs. Buy Analyzer
An honest comparison that accounts for opportunity cost, taxes, and the true cost of ownership.