How We Calculate Real Build Cost
Transparency is the point. Here's exactly how we arrive at every number on this site.
The Problem
Solar kit prices are misleading. A kit advertised at $289 might not include a battery or inverter — components that could cost another $750. The advertised price tells you what the manufacturer is selling, not what you'll actually spend to power anything.
We built OffGridEmpire to fix this. Every kit on this site is broken down into its component parts, checked for completeness, and priced for what it actually costs to build a working system.
Kit Decomposition
Every solar kit is decomposed into 7 standard component roles:
For each role, we record whether it's included in the kit, partially covered, or completely missing. This produces the completeness score — a simple percentage of how many required roles are covered.
Real Build Cost Formula
Only required missing components count toward real build cost. Optional upgrades (like Bluetooth monitoring for a kit that already has an LCD display) are shown separately and do not inflate the total.
Missing Component Pricing
When a kit is missing a required component, we estimate the cost to add it based on:
- Compatibility— the replacement must match the kit's voltage, chemistry, and capacity requirements
- Market pricing — we use current prices from major retailers for popular products in the required spec range
- Conservative estimates — we estimate mid-range, not the cheapest possible option, to avoid understating the real cost
Price Data Sources
All pricing data comes from legitimate sources:
- Amazon Product Advertising API (affiliate program)
- Manufacturer affiliate data feeds (ShareASale, Impact)
- Direct manufacturer partnerships
We do not scrape retailer websites. All data is obtained through official API access or affiliate program data feeds.
Update Frequency
Prices are pulled every 6-12 hours depending on the source. Every price on the site displays a last updatedtimestamp. If a price hasn't been updated in more than 24 hours, the site shows a stale data warning. Always verify the current price at the retailer before purchasing.
Cost Per Watt-Hour
For kits that include battery storage, we calculate cost per usable watt-hour as the universal comparison metric:
"Usable" accounts for depth of discharge. A 100Ah AGM battery at 50% DoD provides ~600Wh usable, while a 100Ah LiFePO4 at 100% DoD provides ~1,280Wh usable. We use manufacturer-recommended DoD for each chemistry.
Use Case Ratings
Each kit is rated for suitability across common off-grid use cases (RV, cabin, shed, emergency, homestead, marine). Ratings consider panel output, storage capacity, inverter size, portability, and expandability relative to typical power needs for each scenario.
Limitations & Disclaimers
- Prices are approximate and may differ from what you see at the retailer. Always verify before purchasing.
- Missing component cost estimates are averages. Your actual cost may be higher or lower depending on the specific product you choose.
- Real build cost does not include sales tax, installation labor, or permits.
- Use case ratings are general guidance, not engineering specifications. Consult a qualified installer for system design.
- OffGridEmpire earns affiliate commissions on qualifying purchases. This does not affect our methodology or rankings.
Frequently Asked Questions
What is 'real build cost'?
Real build cost is the total you would actually spend to have a complete, functional off-grid solar system. It includes the kit's advertised price plus the estimated cost of any required components that aren't included in the kit.
How do you determine which components are missing?
We decompose every kit into 7 standard component roles: solar panels, charge controller, battery bank, inverter, wiring, mounting hardware, and monitoring. If a kit doesn't include one of the required roles, we flag it as missing and estimate the cost to add it.
Where do the missing component prices come from?
Missing component cost estimates are based on the average market price for a compatible component of that type. For example, if a kit is missing a 12V 100Ah LiFePO4 battery, we estimate based on current prices for popular batteries in that spec range from major retailers.
How often are prices updated?
We pull prices from retailer APIs and affiliate data feeds every 6-12 hours. Every price on the site shows a 'last updated' timestamp so you can see exactly how fresh the data is. If a price is more than 24 hours old, we display a stale data warning.
What does 'completeness' mean?
Completeness is the percentage of required component roles that are included in the kit. A 100% complete kit includes everything you need to set up a functional system. A 57% complete kit is missing several critical components and will require significant additional purchases.
Do you account for taxes and shipping?
We include known shipping costs and freight surcharges when reported by the retailer. We do not estimate sales tax because it varies by state and jurisdiction. Real build cost is always shown before tax.