Cost per Kilo: Simple Accounting for Lettuce Farms

Cost per Kilo: Simple Accounting for Lettuce Farms

Cost per kilo hydroponic lettuce is the number that decides whether a farm reaches year two, and most farms do not calculate it until a buyer asks for a fixed price. The model is not complicated: add up what a cycle costs, divide by what it packed, and test the answer against a price that holds for a year. The difficulty is allocation, not arithmetic. This article sets out the cost buckets, where overhead belongs, how to allocate by batch or by square metre week, and why cycle time moves it more than any input price.

Cost per Kilo Hydroponic Lettuce: The Cost Buckets

Six buckets carry nearly all the cost in a leafy crop. Right boundaries matter more than precise numbers, because a cost in the wrong bucket is allocated to the wrong crop.

Two behave differently from the rest. Energy and labour scale with area and weeks, so a crop sitting one week longer costs more without producing more. Plants, media and packaging scale with head count and fall as pack-out rises.

Direct vs Overhead and What Sits Where

Direct costs can be traced to one batch: the plugs for that batch, the packaging it left in, the hours booked to it. Overhead cannot: rent, structure and equipment depreciation, insurance, software, management salary, and the maintenance line that keeps pumps and dosing running.

The usual mistake is leaving overhead out because it is already in the bank account. A farm that prices against direct costs only will look profitable at crop level and run short of cash at year end. The choice between contract and in-house maintenance belongs in this bucket and changes both the annual figure and how lumpy it is.

Depreciation is the part owners argue about. Structures are commonly written off over 10 to 20 years, gutters and tanks over 7 to 10, and pumps, dosing units and sensors over 3 to 5, the service life those items give in a wet, fertilised environment. Apply one method consistently, since switching mid-year moves cost per kilo without changing anything physical.

Allocation by Batch and by Square Metre Week

There are two honest ways to spread overhead; the better one depends on whether the farm runs batches or continuous weekly sowings.

• By batch: period overhead divided by the batches harvested in the period. Simple, and it distorts when batch sizes differ.
• By square metre week: the overhead pool divided by total m²-weeks grown, then charged to each crop by the area and weeks it occupied. Slower to set up, and the only method that shows why a slow crop costs more.

A third shortcut, charging overhead as a flat percentage of direct cost, is common and dangerous. It hides the fact that a 30-day crop and a 45-day crop consume very different amounts of the same fixed base. Where the farm sells more than one crop, m²-week allocation makes the mix visible.

Allocation method is a business decision, not a spreadsheet detail.

Cost per kilo is a capacity question before it is a purchasing question. A farm that shaves three days off a cycle at unchanged quality lowers cost per kilo permanently; a farm that negotiates two cents off a tray lowers it once. With limited review time, spend it on cycle time and pack-out rate first.

Cycle Time: The Quiet Multiplier

Cycle time multiplies because it moves the numerator and the denominator at once. Fewer days per crop means more crops per year from the same area, more kilos to spread fixed cost over, and less energy and labour per kilo. A crop moved from 35 days to 30 days raises annual turns by roughly 17%, which alone can take double digits off cost per kilo.

Cycle time is not free to shorten. Pushing density or temperature to finish faster raises disease pressure and lowers head weight, and the arithmetic turns against the farm when a 15% shorter cycle comes with a 15% lighter head. Track cycle time with head weight and pack-out rate, never alone; the core KPI set for yield per m² and labour hours treats the three as one group.

A Worked Example with Round Numbers

Take a 1,000 m² house running NFT lettuce at 25 plants per m², a 35-day cycle, an average head of 250 g and 90% pack-out. Plants per cycle are 25,000; gross weight is 6,250 kg; packed weight is about 5,600 kg.

Read that number as a starting point, not a benchmark. Labour in the example is about 2,000 hours a year across crop work, pack house and clean-down, which suits a compact farm with good layout; long carry distances can double it. At 30 days and 95% pack-out, the same inputs land lower.

Sensitivity: Power Price and Labour Rates

Two inputs move fast enough to justify a standing sensitivity table, and one crop variable moves faster than either.

The lesson is where effort belongs. Nutrient price rarely moves the number; pack-out rate and cycle time always do. A farm chasing discounts at 80% pack-out is optimising the smallest line in it.

Using Cost per Kilo to Price Contracts

Once cost per kilo is stable, pricing becomes a margin decision rather than a guess. A contract fixing price for twelve months transfers input risk to the grower, so the model needs a margin buffer sized to the sensitivity above and a clause revisiting price if power or labour moves beyond a stated band.

• Floor price: cost per kilo plus the buffer; refuse volume that cannot clear it.
• Cost-plus structures: suit retail programmes where the buyer accepts a reviewed cost base each season.
• Mix discipline: price by m²-week, so a slow crop is charged for the space it holds.
• Re-baseline quarterly: recompute with actual pack-out and hours, since first models are optimistic.

A cost per kilo hydroponic lettuce model also feeds the capital decision: run the same model forward with the new fixed cost and volume, which is what the ROI and payback model for hydroponic farms does with the equipment spend included. The selling side is covered in the notes on channels, contracts and pricing discipline, and the schedule that keeps the number steady is the one that keeps sowings even, as set out in the guide to crop scheduling for continuous production. Weekly recording keeps inputs honest, which is the case for written standard operating procedures.

Frequently Asked Questions

What is a realistic cost per kilo for hydroponic lettuce?
A: All-in figures commonly land between 1.00 and 2.00 per kg depending on scale, labour rate, energy price and whether the house is lit. Model yours first.

Should overhead be included in cost per kilo?
A: Yes. Excluding rent, depreciation and management is the usual reason a farm shows a crop margin and runs short of cash.

How do I allocate shared costs between lettuce and herbs?
A: Charge by square metre week: area times weeks occupied spreads the fixed base by actual use.

Which input moves cost per kilo the most?
A: Cycle time and pack-out rate. Shortening a cycle from 35 to 30 days, or lifting pack-out from 80% to 90%, outweighs most price negotiations.

How often should cost per kilo be recalculated?
A: Quarterly with actual pack-out and hours, and after any energy tariff change or shift in cycle length.

Get the Cost per Kilo Worksheet

A cost per kilo hydroponic lettuce model earns its keep when it is rebuilt each quarter with real pack-out and hours, then used to decline volume that does not clear the floor. To ask for our cost-per-kilo worksheet with the formulas already linked, send the growing area, cycle length and labour rate.

• Farm KPIs: yield per m² and labour hours
• Selling channels, contracts and pricing discipline
• ROI, cost per area and payback period