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What will it cost? What will it save? Do the math first.
Calculators for solar, home batteries, heating and electricity bills, for homeowners in the US, UK, Canada and Australia.
Solar
Payback, panel output and system size: what solar costs and what it saves on your bill.
4 calculators →
Batteries & Backup
Size a home battery, inverter, generator or portable power station for outages and time-of-use rates.
4 calculators →
Heating & Cooling
Insulation, heat pumps, air conditioning and heater running costs.
4 calculators →
Electricity Costs
What your appliances cost to run, what you pay per kWh and your home's carbon footprint.
6 calculators →
All calculators
18 live · more added monthly| Calculator | Topic | Answers | Open |
|---|---|---|---|
| Solar Payback Calculator | Solar | How many years until solar panels pay for themselves, with export credits, price rises and... | Open → |
| Solar Panel Calculator | Solar | How many solar panels you need, what size system and how much roof space, from your electr... | Open → |
| Solar Panel Output Calculator | Solar | How many kWh a solar panel or system produces per day, month and year where you live. | Open → |
| Solar Battery Payback Calculator | Solar | How long a home battery takes to pay for itself by storing solar and shifting cheap off-pe... | Open → |
| Attic Insulation Cost Calculator | Heating & Cooling | How many inches of insulation you need to reach the recommended R-value, what it costs and... | Open → |
| Space Heater Cost Calculator | Heating & Cooling | What a space heater costs to run per hour, day and month at your electricity price. | Open → |
| AC Running Cost Calculator | Heating & Cooling | What a window, portable, mini-split or central air conditioner costs to run per hour, mont... | Open → |
| Tankless vs Tank Water Heater Calculator | Heating & Cooling | Compare running costs of gas and electric tank, tankless and heat pump water heaters, with... | Open → |
| Generator Size Calculator | Batteries & Backup | What size generator you need: running and starting watts for the appliances you want to ke... | Open → |
| Battery Runtime Calculator | Batteries & Backup | How long a portable power station or home battery will run your appliances, with or withou... | Open → |
| Home Battery Size Calculator | Batteries & Backup | How many kWh of battery backup you need for an outage, and how much power it must deliver... | Open → |
| Inverter Size Calculator | Batteries & Backup | What size inverter you need: continuous and surge watts for your appliances, plus battery... | Open → |
| LED Savings Calculator | Electricity Costs | How much switching to LED bulbs saves a year in electricity and replacement bulbs, and how... | Open → |
| Home Electricity Carbon Footprint Calculator | Electricity Costs | The CO2 from your home electricity using your country, state or province grid factor, with... | Open → |
| Electricity Cost Calculator | Electricity Costs | What any appliance costs to run per hour, day, month and year at your electricity price. | Open → |
| EV Charging Cost Calculator | Electricity Costs | What it costs to charge an electric car at home and at public chargers, per month, per mil... | Open → |
| kWh Cost Calculator | Electricity Costs | Turn kWh into money: your bill with fixed charges and tax, and the real price you pay per... | Open → |
| EV vs Gas Calculator | Electricity Costs | Compare the yearly running cost of an electric car and a petrol car, and how long the EV t... | Open → |
We show our working
Every result comes with the formula, the assumptions behind it and a worked example. If a number looks off, you can see exactly why.
- 01Enter numbers from your bill
- 02Read the result and the formula
- 03Compare it with quotes you get
Solar payback · exampleUSD
8 kW × 4.5 h × 365 × 0.810,512 kWh
× $0.182 per kWh$1,913/yr
8,000 W × $2.60$20,800
$20,800 ÷ $1,913
Payback10.9 years