Solar Sizing
Energy Consumption Audit Calculator
Add up daily, monthly and annual kWh from your appliances
Updated July 12, 2026 · Live
What this tool does
Adds up the daily, monthly and annual energy use of your appliances so you can size a solar system to the load it actually has to carry.
Enter each appliance’s watts, hours per day and quantity; the calculator totals your daily, monthly and annual energy use in kWh.
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Formula Used
How the energy consumption audit works
It multiplies each appliance’s power by the hours it runs each day and by how many you have, sums those figures, and divides by 1000 to convert watt-hours to kilowatt-hours. Monthly use is the daily figure over an average 30.44-day month; annual use is the daily figure across 365 days. The running average draw in watts is the daily energy spread evenly over 24 hours.
What you enter
Enter each appliance’s watts, hours per day and quantity; the calculator totals your daily, monthly and annual energy use in kWh. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
The daily kWh figure is the number every other sizing tool starts from. Feed it into the Solar Array Sizing and Battery Bank Capacity calculators to turn a load into a panel count and a battery bank.
Safe by design
This calculator does the arithmetic of sizing — quantities, geometry and cost. It deliberately stops at the line a certified installer must sign off. It will never tell you a cable or fuse size, an earthing arrangement, a battery charge voltage, or a roof structural load: those are regulated calculations where a wrong number causes fire, electrocution or collapse. All electrical work must be carried out by a qualified, certified installer, and this page is not an installation guide.
Assumptions and limits
Nameplate wattage is a maximum, not an average — fridges, pumps and heat sources cycle on and off, so a metered reading over a week is more accurate than a plate rating. Motor-driven appliances also draw a brief surge at start-up that this steady-state total does not capture.
Using it with the rest of BuildMetricLab
This calculator is one step in planning a system. Pair it with the other solar sizing, geometry and cost tools to go from an energy figure to a panel count, a layout and a costed bill of materials. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Adds up the daily, monthly and annual energy use of your appliances so you can size a solar system to the load it actually has to carry. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or tariffs are embedded.
Frequently asked questions
How do I find an appliance’s wattage?
It is printed on the rating plate or in the manual, usually as watts (W) or as volts × amps. If only amps are given, multiply amps by the supply voltage to get watts.
Why total three appliances rather than one figure?
Grouping the big, medium and always-on loads separately makes it clear where the energy goes. Run the tool again for more appliances and add the daily kWh totals together.
Does this size my solar system on its own?
No — it produces the daily energy demand. Take that number into the array-sizing and battery-bank calculators, which turn demand into panel count and storage.
Should I use the nameplate or a measured figure?
A measured reading from a plug-in energy monitor over a full week is the most reliable, because it captures real cycling. Nameplate wattage tends to overstate continuous draw.
Spotted something off?
Calculations or display — let us know.