What this calculator does: You enter the size and unit price of each major off-grid system (solar panels, battery bank, water storage and heating), an allowance percentage for the inverter, charge controller and wiring, optional dollar amounts for cooling and other costs, and a contingency percentage. The calculator totals everything into a budget with each category’s share of the whole.
Who it’s for: People planning an off-grid build who have sized their systems, for example with our other calculators, and want a rough first-pass budget before they start collecting quotes.
The answer it produces: A table of estimated cost by category (solar panels, battery bank, inverter/charge controller/wiring, water storage, heating, cooling and other costs if you entered them, and contingency), each category’s share, and an Estimated Total Budget.
Important limitation: The starting prices are rough do-it-yourself hardware guesses, not quotes, and the tool only adds up what you type in. It leaves out land, buildings, permits, labor, pumps and plumbing, fuel and every ongoing or replacement cost unless you type a dollar amount for them into the cooling and other-costs fields. Your total is only as good as the prices and sizes you enter.
Build Your Off-Grid Budget
Get your sizes first: the panel count from our solar calculator, a battery capacity in kilowatt-hours (the battery runtime calculator shows how long a given size will last) and a tank size from the rainwater calculator. Then replace every starting price with a real quote, and add your own figures for cooling and other costs if you have them.
Off-Grid System Cost & Budget Calculator
How the Calculation Works
When you press Calculate Total Budget, the tool first checks that every field is a number of zero or more, then does simple arithmetic in your browser:
- Solar panels. Number of panels × cost per panel.
- Battery bank. Capacity in kWh × cost per kWh.
- Inverter, charge controller and wiring. The allowance percentage (30% by default) applied to the solar and battery costs added together.
- Water storage. Tank size in gallons × cost per gallon.
- Heating system. The dollar amount you type in, used as is.
- Cooling and other costs. Two optional dollar amounts, used as is. A line appears in the results only if the amount is more than zero.
- Contingency and total. Everything above makes a subtotal. The contingency percentage is applied to that whole subtotal, and the total is the subtotal plus the contingency.
- Shares. Each line divided by the total, rounded to a whole percent.
Inputs and Assumptions
| Input | Starting value | Notes |
|---|---|---|
| Number of Solar Panels Needed | 8 | Take this from the solar calculator, which sizes with 400-watt panels. |
| Cost per Panel ($) | 300 | About $0.75 per watt for a 400-watt panel. Hardware only. |
| Battery Bank Capacity (kWh) | 10 | Usable storage in kilowatt-hours, not amp-hours. |
| Cost per kWh ($) | 400 | Battery hardware only. |
| Water Storage Tank Size (gallons) | 1,500 | The rainwater calculator’s example needs 7,200 gallons, so check yours. |
| Cost per Gallon of Storage ($) | 0.75 | Depends heavily on tank material and size. |
| Balance-of-System Allowance (% of solar + battery) | 30 | Covers the inverter, charge controller, racking, wiring, breakers and disconnects. The field suggests 0 to 200. Set it to 0 if your quotes already include those parts. |
| Estimated Heating System Cost ($) | 2,000 | Equipment such as a stove and chimney, not fuel. |
| Cooling / Ventilation ($) | 0 | Optional. For example the cost of an earth tube or fan system. |
| Other Costs ($) | 0 | Optional. Well, septic, generator, tools and similar items you want in the total. |
| Install/Contingency Buffer (%) | 20 | Applied to the whole subtotal. Must be 100 or less. |
A blank field counts as zero. A negative number or an entry the tool cannot read as a number stops the calculation with a message asking for zero or more in every field. The number of panels must be a whole number, and the buffer cannot be more than 100 percent.
And these are the assumptions built into the tool:
| Assumption | Value used |
|---|---|
| Inverter, charge controller and wiring | 30% of solar plus battery by default, editable |
| Heating | One lump sum, not linked to your heating calculation |
| Prices | One price per unit, no volume discounts, tax or shipping |
| Not included unless you type it in | Land, structures, permits, labor, cooling, pumps, plumbing, generators, and anything else you do not put in the cooling or other-costs fields |
| Never included | Fuel, maintenance, battery replacement, financing and incentives |
What the Result Means
- Each category line. The up-front purchase cost of that system, using your prices.
- Share. Where the money goes. A category with a big share is where a price change matters most. Shares are rounded, so they can add to a little over 100%.
- Cooling / Ventilation and Other Costs. Shown only if you entered an amount. They are added as you typed them, and they are part of the subtotal the contingency is applied to.
- Install/Contingency Buffer. Extra money for surprises and installation. It is a percentage of the subtotal, not a separate estimate of labor.
- Estimated Total Budget. A planning number for the items you entered. It is not a quote and not the cost of going off-grid.
- The priority-order note. The tool also prints a general suggestion to tackle water and shelter first, then power, then heating and cooling, then livestock and garden infrastructure. It is a generic rule of thumb, not a plan for your site.
Example Calculation
Using the calculator’s starting values: 8 panels at $300, a 10 kWh battery at $400 per kWh, a 30% balance-of-system allowance, a 1,500 gallon tank at $0.75 per gallon, a $2,000 heating system, no cooling or other costs and a 20% buffer.
| Category | Calculation | Cost | Share |
|---|---|---|---|
| Solar panels | 8 × $300 | $2,400 | 17% |
| Battery bank | 10 × $400 | $4,000 | 29% |
| Inverter/charge controller/wiring | 30% × ($2,400 + $4,000) | $1,920 | 14% |
| Water storage | 1,500 × $0.75 | $1,125 | 8% |
| Heating system | As entered | $2,000 | 15% |
| Install/contingency (20%) | 20% × $11,445 subtotal | $2,289 | 17% |
| Estimated Total Budget | $11,445 + $2,289 | $13,734 | 100% |
Adjusting the example for the real world. The starting prices are on the optimistic, do-it-yourself end. The U.S. Department of Energy’s 2024 benchmark for a professionally installed residential solar system is about $2.78 to $2.95 per watt, covering panels, inverter, mounting, wiring, installation labor and other soft costs. For the example’s eight 400-watt panels (3,200 watts) that is roughly $8,900 to $9,400, compared with the tool’s $2,400 for panels plus about $720, which is the 30% allowance applied to the panel cost alone. That benchmark is for grid-tied systems and is not the same as an owner-built off-grid system, but it shows the size of the gap between hardware and a finished installation.
Batteries show the same pattern. The DOE benchmark for solar plus a 13.5 kWh battery is about $1.55 to $1.64 per watt above the solar-only figure for an 8 kW system, which works out to roughly $900 to $970 per kWh of installed storage, against the tool’s $400. Water is different again. The Texas Water Development Board says storage tanks dominate the cost of a home rainwater system, and it cites $8,000 to $10,000 for storage at typical homes.
The allowance is a planning figure, not a measured one. This Old House’s off-grid cost guide lists inverters at $7,000 to $8,000 and charge controllers at $550 to $600 each, and those are prices for whole-house systems. The example’s 30% allowance is $1,920, so if you expect a large inverter, replace the percentage with quotes, and set it to 0 if your quoted prices for the panels and battery already include the inverter and controller.
See how quickly the total moves when you swap in more realistic numbers:
| Scenario | Battery cost | Tank | Buffer | Estimated Total Budget |
|---|---|---|---|---|
| Starting values | $400 per kWh | 1,500 gal | 20% | $13,734 |
| Installed-battery price | $900 per kWh | 1,500 gal | 20% | $21,534 |
| Plus the rainwater example’s tank | $900 per kWh | 7,200 gal | 20% | $26,664 |
| Plus a bigger buffer | $900 per kWh | 7,200 gal | 30% | $28,886 |
The total roughly doubled without any change to the system itself. Entering $1,500 for cooling and $5,000 for other costs, such as a well, would add $7,800 to the starting-values total once the 20% buffer is applied. That is the calculator’s main lesson: the arithmetic is easy and the prices are what matter.
How to Use the Result in a Real System
- Size before you price. Use the solar, battery runtime, heating and rainwater calculators first, so the quantities you enter come from real sizing and not guesses.
- Replace every starting price with a quote. Get two or three, and decide whether you will install things yourself or hire it out, since that changes the numbers more than anything else.
- Add what the tool leaves out. Write down land, structures, permits, cooling, water pumps and plumbing, backup generator, tools and delivery. Type the ones you can price into the cooling and other-costs fields, and add the rest to your total by hand.
- Raise the buffer for hard projects. A remote site, a first build or a lot of unknowns is a reason to go above 20%. Watch the total under two or three scenarios.
- Check incentives, but do not count on them. Programs change. The DSIRE database lists federal and state incentives, and the DOE benchmark figures above do not include subsidies.
- Budget the running costs separately. Fuel, maintenance and battery replacement do not appear here. The U.S. Energy Information Administration publishes weekly residential heating oil and propane prices during the heating season, and our heating fuel calculator and firewood calculator show how much fuel you might use.
- Phase the purchases. Use the shares to decide what to buy first and what can wait, and run the calculator again as prices change or you finish each stage.
Important Variables That Can Change the Result
- Installing it yourself or hiring it out. The largest single swing, as the DOE benchmark comparison above shows.
- Local prices and delivery. Prices vary by region, supplier and season, and remote sites pay more for freight.
- Battery type and quality. Chemistry, warranty and usable capacity all change the price per kWh.
- Real inverter and wiring costs. The 30% allowance can be changed, but it is still a percentage. It may be too low or too high for your system, especially with large loads or long wire runs.
- Tank material and size. Plastic, steel and concrete cisterns differ widely in cost per gallon, and so does what it takes to install them.
- Heating choice. A simple wood stove and a full central system are very different budgets.
- Permits and codes. Local rules can add inspections, engineered plans and required equipment.
- Incentives and financing. Neither is modeled, and both can change your out-of-pocket cost.
Common Mistakes
- Leaving the starting prices in place. They are placeholders, not market prices.
- Treating the total as a quote or a loan amount. It is a planning number.
- Forgetting the excluded items. Land, structures, permits and cooling can dwarf the systems the tool covers. Cooling and other costs count only if you enter them.
- Entering fuel cost as the heating system. The heating field is for equipment. Fuel is a yearly cost and is not in the total.
- Mixing up units. Battery size is in kilowatt-hours, not amp-hours or watts, and the panel field wants a count of panels, not total watts.
- Double counting the inverter. If your battery or panel prices already include an inverter and controller, the allowance adds them again. Set the allowance to 0 in that case.
- Setting the buffer to zero. Most builds cost more than the first estimate.
- Entering water demand instead of tank size. The field wants the size of the tank you will buy.
When This Calculator Should NOT Be Used
- As a quote, contract or loan application. Use written quotes from suppliers and installers.
- To work out payback or return on investment. It has no energy savings, fuel costs or lifespans.
- To compare off-grid with grid-tied power. It has no utility rates or connection costs.
- To budget a whole homestead. Land, the house and food production are outside its scope.
- For commercial or large systems. The percentage allowance and single prices are for small homes.
- Before you know your system sizes. Do the sizing first, or the total means very little.
Related Honey Hen Calculators
- Off-Grid Solar Calculator: the panel count for this budget.
- Battery Bank Runtime Calculator: test how long a battery size will last.
- Rainwater Catchment Calculator: the tank size for the water line.
- Off-Grid Heating Fuel Calculator: estimate the fuel your heating system will use.
- Off-Grid Home Cooling: enter the cost of a cooling system in the cooling field.
- Firewood Calculator: how much wood you might burn.
- Homestead Livestock Calculator and Garden Size Calculator: food production has its own separate budget.
- All Homestead Calculators: the full set of planning tools in one place.
Related Honey Hen Articles
- Hidden Costs Solar Installation: What to Avoid
- DIY Off-Grid Solar Installation: A Step-by-Step Guide
- DIY Affordable Off-Grid Living Tips
- Cash in the Wild: Off-Grid Living Financial Hacks
Authoritative Sources
- U.S. Department of Energy: Solar Photovoltaic System Cost Benchmarks. Cost per watt for residential solar and solar-plus-storage systems in 2024 dollars, with the components included and a note that subsidies are excluded.
- Texas Water Development Board: Rainwater Harvesting FAQ. Notes that storage tanks are the largest installation cost of a home rainwater system.
- DSIRE: Database of State Incentives for Renewables and Efficiency. A searchable database of federal and state incentives, run by the N.C. Clean Energy Technology Center.
- This Old House: Guide to Off-Grid Solar System Costs. Price ranges for off-grid panels, batteries, inverters and charge controllers.
- U.S. Energy Information Administration: Heating Oil and Propane Update. Weekly residential heating oil and propane prices during the heating season.
Off-Grid Budget Calculator FAQ
How much does it cost to go off-grid?
It varies enormously with system size, climate, land, how much you build yourself and where you live. This calculator does not give a typical cost. It adds up the sizes and prices you enter, so its answer is only as good as those inputs.
Are the default prices accurate?
They are rough do-it-yourself hardware guesses. Professional installation costs considerably more, as the DOE benchmark shows, and prices change with region, supplier and time. Replace them with quotes.
What’s not included in this budget estimate?
Land, buildings, permits, labor, water pumps and plumbing, backup generators, fuel, maintenance, battery replacement, financing and incentives are not included unless you add a dollar figure for them in the cooling or other-costs fields. Livestock and garden costs are also separate.
What is the 30% for inverter, charge controller and wiring?
An allowance calculated on your solar and battery costs combined, set to 30% by default. It is a rough placeholder that you can edit. Get real prices for these parts, and set the allowance to 0 if your quotes already include them.
What buffer percentage should I use?
The calculator starts at 20%. Use more for a remote site, a first-time build or an unclear scope. Try the total at two or three percentages to see the range.
Does the total include tax credits or incentives?
No. Incentives change over time and vary by state and program. Check the DSIRE database for what is currently available where you live.
Should I buy everything at once or phase it in?
Many homesteaders phase in major systems over a few years, prioritizing water and shelter first, then power, then refining the rest. Seeing your full estimated total up front helps you decide what to prioritize and what can wait.
This calculator provides general planning estimates using editable default unit costs, not real quotes. Actual prices vary significantly by region, supplier, and over time — get quotes from local suppliers and installers before finalizing your budget.
