Off-grid planning tool

Tiny House Solar Calculator

Estimate daily energy use, battery capacity, solar panel wattage, inverter output, and a few system options that fit your numbers.

Battery capacity and inverter output are separate

Battery capacity, measured in kWh, estimates how long your power lasts. Inverter output, measured in watts or kW, estimates what can run at the same time. A large battery can still struggle if the inverter is too small for appliances that start together.

Appliances

Add the devices you expect to run in your tiny house. Presets are planning estimates and every row stays editable.

Appliance	AC watts	Startup watts	Hours/day	Qty	Daily Wh	Remove

Running total: 0 Wh per day

Enter AC watts at the outlet: this calculator models AC loads only, not 12V/USB DC devices. Startup watts are optional. If left at 0, the calculator uses normal watts for peak inverter sizing. Use whole numbers for quantity. Decimals round to the nearest whole number.

Fridge cycling: refrigerators do not pull their full wattage all day. Presets use 8 hours/day as a simple planning average.

Vampire power: always-on items like routers, chargers, clocks, and standby electronics can quietly add up over 24 hours.

System settings

Use local solar conditions and your preferred backup assumptions.

Battery backup days How many cloudy days the batteries should cover. Peak sun hours 4 is only an example starting value. For your location, enter your address in NREL's PVWatts Calculator and use the "Solar Radiation (kWh/m²/day)" result: each kWh/m²/day equals one peak sun hour. Solar delivery factor (%) 80% is an editable planning assumption for the combined path from rated panel output to appliance AC energy, including heat, wiring, charging/storage and inverter conversion. It is not a measured efficiency for your equipment. Inverter idle draw and recovery of an already depleted backup bank are not included. Changing DIY inverter efficiency changes battery sizing only; revise this combined solar factor separately for your system. DIY battery type DIY battery bank only. Sets the depth of discharge below; 80% and 50% are editorial starting points. Power stations use their own built-in rules. DIY battery depth of discharge (%) Usable share of the DIY battery before recharge. 100% is a math scenario only; follow your battery/BMS limits. DIY inverter efficiency (%) 85% is an editable planning assumption, not a measured or guaranteed value. Use the conversion efficiency without idle draw if you enter idle separately below; 100% is an idealized, loss-free scenario. Inverter on-hours per day How long the inverter or power station AC output stays switched on each day, including times nothing is running. 24 is an editable continuous-backup assumption. Can't be less than your longest appliance hours. Inverter idle draw, battery side (W, optional) Leave blank to exclude it (results will say so). 0 means a zero-allowance scenario, not proof of zero draw. Use your inverter's no-load consumption from its manual. Inverter safety margin (%) Extra room above estimated peak load.

Size solar for winter A yearly average hides the darkest months. Check this if you'll rely on solar in winter, then enter your local winter sun hours.

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Estimated results

Total daily energy 0 Wh 0 kWh per day

DIY battery bank needed 0 Wh 0 kWh needed for backup time

Solar panel size 0 W Appliance energy only.

Estimated peak load 0 W Assumes every appliance starts at the same time. Uses startup watts where entered, otherwise running watts.

Inverter output needed 0 W Based on estimated peak load plus the inverter safety margin.

Limits of these estimates:

Not modeled: battery temperature, battery aging, and the reduced capacity of lead-acid batteries at high discharge rates. Fridge and freezer hours and preset startup watts are rough averages; use measured or manufacturer-confirmed values for your appliances.

Opens your browser's print window. Choose "Save as PDF" to keep a copy. This site does not save your entries.

Power stations and kits compared with your numbers

A power station is shown as within limits only if its own energy estimate, rated AC output, and solar input all pass under the stated assumptions. Your DIY battery settings are not applied to power stations. Specs were checked in October 2026; confirm current specs and final sizing before buying.

This calculator gives a rough planning estimate only. It is not a final electrical design. Consult a qualified electrician or solar professional before buying or installing equipment. Permanent systems may need a permit under your local electrical code. The federal Residential Clean Energy Credit (Section 25D) is unavailable for new installations completed after December 31, 2025. Unused credits from earlier qualifying installations may still carry forward. State and utility incentives may differ.