Compare calculators
Both calculators run independently — change the inputs on either side to compare results.
Appliance Energy Cost Calculator
Calculate the true annual electricity cost of any appliance using its wattage, daily usage hours, days per week, your electricity rate, and the number of units. Essential for budgeting solar or identifying energy hogs.
Annual running cost
262.08 $/yr
$100-300/yr marks a major load like a space heater or old fridge. The $262 example heater costs about $22/month; cutting use 2 h/day would save around $90/yr.
Annual cost scales directly with watts, runtime, and rate; the US average residential rate is about $0.16/kWh, the basis of the verified $262/yr example for a 1500 W heater run 3 h/day.
Solar Panel System Sizing Calculator
Calculate exactly how many solar panels your home needs based on your electricity bill, local sun exposure, panel wattage, and desired offset. Ideal for homeowners planning a rooftop PV installation.
Solar panels needed
21 panels
9.33: 7-10 W per monthly kWh is the normal range for a 100% offset at 4.5-5.5 sun hours. The example (9.3 W/kWh: 21x400W panels for 900 kWh) sits here.
This is installed watts per kWh of monthly usage; the formula's own math ties panel count to your offset target, sun hours, and losses, with ~7-13 W per monthly kWh being typical.
Key differences
| Appliance Energy Cost Calculator | Solar Panel System Sizing Calculator | |
|---|---|---|
| Category | Solar Energy | Solar Energy |
| Inputs required | 5 | 5 |
| Result | Annual running cost ($/yr) | Solar panels needed (panels) |
| What it does | Calculate the true annual electricity cost of any appliance using its wattage, daily usage hours, days per week, your electricity rate, and the number of units. Essential for budgeting solar or identifying energy hogs. | Calculate exactly how many solar panels your home needs based on your electricity bill, local sun exposure, panel wattage, and desired offset. Ideal for homeowners planning a rooftop PV installation. |