How big a solar system does a 100-cow dairy need?

A 100-cow dairy milking 2x/day with 500 gallons/day hot water uses approximately 115-130 kWh/day, requiring a 30-40 kW solar system (75-100 panels). With USDA REAP (40%), ITC (30%), and MACRS (~26%), net cost can drop to under $30,000 on a $150,000 system — payback under 1 year in most states.

Is solar cost-effective for small dairies under 50 cows?

Yes — small dairies benefit from the same REAP/ITC/MACRS incentive stack as large ones. A 50-cow dairy needs a 15-20 kW system costing $40,000-$55,000 gross. With REAP (40%) plus ITC (30%) plus MACRS (~26%), net cost can be under $5,000. Annual savings of $12,000-18,000 mean payback under 1 year. Apply to USDA REAP before installation to lock in the grant.

Solar Dairy Farm Calculator

Enter your herd size and monthly bill — get system kW, USDA REAP grant estimate, ITC + MACRS tax benefits, and payback period with and without incentives.

Dairy operation

Herd size (milking cows)?

cows

Milking sessions per day?

Water heating (gallons/day)?

gal/day

Monthly electric bill?

Roof/ground area available?

sqft

State?

USDA REAP grant (apply?)?

Enabled

Dairy solar system

92.6 kW system — 232 × 400W panels

Energy breakdown (daily)

Vacuum pump (milking)50 kWh/day

Bulk tank cooling14 kWh/day

Water heating31.3 kWh/day

Lighting + misc5 kWh/day

Total daily load100.3 kWh/day

Costs & incentives

Gross system cost$240,741

Federal ITC (30%)-$72,222

MACRS depreciation benefit-$62,593

USDA REAP grant (est.)-$96,296

Net cost with REAP$9,630

Annual savings$14,600/yr

Payback with REAP0.7 yrs

25-year NPV$244,602

Link copied to clipboard

How to Use This Calculator

Enter your herd size and milking operations

Enter the number of milking cows, milking sessions per day, and daily hot water usage. The calculator breaks down energy into four components: vacuum pump (milking), bulk tank cooling, water heating, and lighting/misc. These four loads account for 85-95% of a typical dairy operation's electricity use.

Enter your bill and available space

Enter your current monthly electricity bill to cross-check against the calculated load. If your bill is higher than the calculated dairy load, the calculator uses your bill as the sizing basis. Enter your usable roof and ground area — barn roofs, parlor roofs, and machine shed roofs all count. Each 400W panel needs approximately 22 square feet.

Enable USDA REAP for accurate net cost

Most dairy farms qualify for USDA Rural Energy for America Program (REAP) grants, which cover 25-50% of project costs up to $500,000. Enable the REAP toggle to see how it changes your net cost and payback period alongside the 30% federal ITC and MACRS depreciation benefits.

The Formula

Vacuum Pump = Cows × Sessions/day × 0.5 kWh Bulk Tank = Cows × 7 gal milk/day × 0.04 kWh/gal Water Heating = Hot Water Gallons ÷ 8 (kWh per 8 gal heated 55°F → 140°F) Misc Lighting = Cows × 0.1 kWh/day Total Daily kWh = sum of all four loads System kW = Daily kWh ÷ Peak Sun Hours ÷ 0.80 REAP Grant = System Cost × 40% (up to $500K for systems ≤100 kW) Net Cost = Gross Cost − ITC(30%) − MACRS(26%) − REAP Grant

The 0.04 kWh per gallon of milk for bulk tank cooling is a USDA-validated benchmark. Vacuum pump energy of 0.5 kWh per cow per session assumes a standard pipeline milking system; newer rotary parlors may use 30% less. MACRS 5-year depreciation provides approximately 26% tax benefit at the 21% corporate tax rate — actual benefit depends on your tax situation, consult your accountant.

Example

Riverside Dairy — 150 cows in Pennsylvania

The Millers run a 150-cow dairy in Pennsylvania, milking 2x/day. Their monthly electric bill averages $3,200. They have 18,000 sqft of south-facing barn roof and plan to apply for USDA REAP.

Herd150 milking cows, 2x/day

Hot water750 gal/day

Monthly bill$3,200

StatePennsylvania (4.4 PSH)

Result

System size~88 kW (220 panels)

Gross cost~$229,000

ITC (30%)-$68,700

MACRS benefit-$59,500

REAP grant (40%)-$91,600

Net cost with REAP~$9,200

Annual savings~$38,400/yr

Payback with REAP~0.2 years

25-year NPV~$640,000

With REAP grant combined with ITC and MACRS, the Miller's net cost drops to under $10,000 for an 88 kW system — an extraordinary return. Even without REAP, the payback is under 4 years. Dairy farms are one of the best solar economics cases in agriculture due to high, consistent electricity loads and multiple federal incentive stacks.

FAQ

What is USDA REAP and do dairy farms qualify? ▼

The USDA Rural Energy for America Program (REAP) provides grants of 25-50% of renewable energy project costs, up to $500,000 for solar. Dairy farms qualify as agricultural operations if they derive at least 50% of gross income from agricultural products. Most family and commercial dairies easily qualify. Applications are accepted year-round with quarterly deadlines. REAP can be combined with the 30% federal ITC and MACRS depreciation, making dairy farm solar economics among the best in commercial agriculture. Contact your state USDA Rural Development office for application details.

What are the main electricity loads on a dairy farm? ▼

The four main dairy electrical loads are: (1) Vacuum pump (25-35% of total) — powers milking units; runs during each milking session. (2) Bulk tank cooling (30-40%) — refrigerates milk from cow body temp (101°F) to below 40°F within 2 hours of milking; the single largest load on many dairies. (3) Water heating (15-25%) — hot water for equipment washing between milking sessions. (4) Lighting, ventilation, manure handling (10-20%) — fans, augers, lighting in barns and parlors. Solar panels produce during daylight, which aligns well with milking, cooling, and washing loads — direct self-consumption rates of 60-80% are common on dairies.

How do I size solar for a dairy farm? ▼

The standard approach: (1) Calculate daily kWh from herd size and operations (this calculator does that). (2) Divide by your location's peak sun hours and 80% efficiency factor to get system watts. (3) Check roof/ground space — each 400W panel needs 22 sqft. (4) For larger dairies (over 200 kW), consider ground-mounted systems in the farmyard. Most dairy operations have ample south-facing barn roof space — a 100-cow dairy needs about 40-50 kW (roughly 5,000-6,000 sqft of roof). Consult a commercial solar installer for a site-specific design, especially if considering ground mounts or pole mounts over feedlots.

What is MACRS depreciation for solar? ▼

MACRS (Modified Accelerated Cost Recovery System) allows solar assets to be depreciated over 5 years using an accelerated schedule. Combined with bonus depreciation provisions, most farms can deduct 80-100% of the system cost in the first year. At a 21% corporate tax rate, a $200,000 system generates approximately $40,000-$42,000 in tax savings. This is separate from and in addition to the 30% ITC. The ITC reduces your tax liability dollar-for-dollar; MACRS reduces your taxable income. Work with an agricultural CPA to optimize both incentives for your specific tax situation.

Is 3x/day milking worth the extra solar investment? ▼

Three-times-daily milking increases milk production 10-15% per cow and increases electricity use approximately 50% (more vacuum pump and cooling time). For the solar decision, 3x milking means a larger system but the same economics — because the extra milk revenue typically more than offsets the extra energy cost. Robotic milking systems (voluntary milking) run continuously and have variable energy profiles, but daily totals are similar to 3x conventional milking. If you're sizing solar for a dairy converting to robotic milking, add 15-20% to the 3x/day estimate for automation, computer, and ancillary loads.

Related Calculators

Embed This Calculator

Free to embed on your website. Just copy this code:

<iframe src="https://solarsizecalculator.com/solar-dairy-farm-calculator"
  width="100%" height="700" frameborder="0"
  title="Solar Dairy Farm Calculator"></iframe>