Inventory management for Shopify HVAC parts stores

The inventory problems HVAC parts stores run into

• Huge variant counts across brands and sizes. A single filter line can have a dozen MERV ratings and a dozen dimensions, each a separate SKU, which makes manual reorder tracking error prone.
• Cross-compatible parts. Capacitors, contactors, and motors often fit multiple equipment brands, so demand for one SKU can spike when a competing part is out of stock elsewhere.
• Mixed fast and slow movers. Filters and belts turn over constantly while compressors and control boards sit for months, so a single reorder rule does not fit the whole catalog.
• Seasonal whiplash. Demand swings hard between cooling season and heating season, and getting caught short during the first heat wave or cold snap costs sales when contractors need parts immediately.
• Bulky or hazardous shipping. Refrigerant, compressors, and large coils often ship freight or have handling restrictions, which can stretch supplier lead times beyond what a small parts SKU would need.

Seasonality and demand

Demand follows the weather, not the calendar. AC parts like capacitors, contactors, condenser fan motors, and refrigerant accessories peak hard in late spring through summer, often spiking fast during the first real heat wave. Furnace parts like igniters, flame sensors, and gas valves peak in fall and early winter, with a similar spike at the first cold snap. Filters and universal parts sell fairly steadily year round. The practical move is to build up stock on seasonal parts before the season starts, not after the first spike hits, since suppliers get slower exactly when everyone else is also reordering the same parts.

Suppliers, lead times and minimums

Suppliers break into a few groups: OEM distributors (Carrier, Trane, Goodman, Rheem parts networks) with set case packs and sometimes minimum order values, generic aftermarket suppliers for universal parts like capacitors and contactors with lower MOQs, and overseas suppliers for commodity items like filters or basic electrical parts where overseas suppliers often take several weeks to ship. Domestic OEM distributors are usually faster but may require a minimum dollar amount per order, and case packs for things like filters or belts are common even on small orders.

Worked example

A store sells a 45uF dual run capacitor at an average of 3 units a day during summer. The supplier lead time is 7 days and the store keeps 4 safety days, so the reorder point is 3 x (7 + 4) = 33 units. The store wants 14 days of cover on top of lead time, so target stock is 3 x (7 + 14) = 63 units. On hand is 20 units with 10 already on order, so order quantity is 63 - (20 + 10) = 33 units. The supplier sells this capacitor in case packs of 10, so the order rounds up to 40 units.

Try it with your own numbers in the reorder point calculator, or size your buffer with the safety stock calculator.

A simple system to start this week

1. List every variant by brand, size, and rating so filters, capacitors, and belts are not lumped into one generic SKU.
2. Set separate lead times per supplier, including longer times for freight-shipped items like compressors and coils.
3. Build in extra safety days for parts that spike during the first heat wave or cold snap, not just an average daily rate.
4. Check each supplier's case pack size and minimum order value so suggested quantities round correctly.
5. Review and approve draft purchase orders weekly, especially in the month before each season starts.
6. Record received stock promptly, including partial shipments, so forecasts and reorder points stay accurate.

How SteadyShelf fits HVAC parts stores

SteadyShelf forecasts demand per variant, accounts for the seasonal swing between cooling and heating parts, and tells you the order-by date for each SKU based on each supplier's lead time, rounding quantities to case packs and minimums. It does not track lot numbers or expiry dates, so if you stock refrigerant or sealants with a shelf life, track those dates outside the app and use SteadyShelf only for the reorder timing and quantity. It also does not handle multi-location transfers, so stores with a separate warehouse and storefront location need to manage those moves manually.

$29/month flat, unlimited products and suppliers, 30-day free trial.

SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.

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