Every assumption is visible
See the formula, the defaults and the sources behind the result. Nothing is scored behind the scenes.
Read the calculation methodologyHome energy decision engine
Know what your energy really costs.
Calculate what you use, what it costs, how long stored energy lasts, and what alternatives could save. Every assumption is shown and every default is editable.
- 1,500 W heater, 8 h/day
- $65.74/mo
- 12.0 kWh/day at $0.180/kWh
- Refrigerator at 35% duty
- $6.90/mo
- 460 kWh/year, not 24 h at nameplate
- 10 kWh battery, 690 W load
- 12 h 0 min
- 8.28 kWh actually reaches AC appliances
These three figures are computed on this page by the same engines the calculators use — no hand-typed marketing numbers.
What do you know?
Start from whatever number you already have. Each route lands on a calculator that can use it directly.
- My electricity billTurn your monthly bill into estimated energy use and compare it with common household loads.Start here
- My monthly or annual kWhPrice your consumption at your own tariff, per day, month and year.Start here
- An appliance's wattageWatts and running hours to real cost, with duty cycle applied.Start here
- My battery sizekWh or Ah in, usable energy and runtime at your load out.Start here
- My solar system sizeAnnual and monthly modelled production with a stated range.Start here
- My EV and chargerWall energy, charge cost, cost per mile and charging time.Start here
Popular calculations
Five areas, one calculation engine behind each. Solar output depends on where the panels are — enter your city, system size, tilt and orientation to estimate monthly and annual production from long-term solar data for your location.
- Electricity costsCalculate what appliances and your household cost to run.Open calculator
- Battery backupFind usable capacity, runtime and backup requirements.Open calculator
- Solar outputEstimate production from long-term solar data for your location.Open calculator
- EV chargingCalculate charging cost, wall energy and time.Open calculator
- Heat pumpsCompare electricity use and running costs against what you heat with today.Open calculator
Learn before you calculate
Worked examples, practical explanations and the physics behind the numbers — checked against the same calculation engines the tools use.
ElectricityHow many watts does a refrigerator use?
A fridge draws its rated watts only while the compressor runs — which is roughly a third of the time. That distinction decides both your bill and your backup sizing.
Read the guide
EV chargingHow long does it take to charge an electric car?
Battery size divided by charger power gives the ideal time. Everything that makes real charging slower is predictable, and most of it is not the charger.
Read the guide
SolarWhat is the best angle for solar panels?
There is no single best angle. There is an angle that maximises the year, an angle that favours winter, and the angle your roof already has — and the gap between them is usually smaller than people expect.
Read the guide
Built to show its work
Exact when it can be. Honest when it can’t.
Conversions can be exact. Solar production and heat-pump savings are estimates, so we label them accordingly.
See every default value and its sourceNo paid result rankings
Commercial relationships never change a calculation. A calculator here is allowed to conclude that an investment does not pay back.
How SnapEnergyLab stays independent