Walk-In Cooler Driving Up Your Electric Bill? Where the Energy Goes

A walk-in is one of the biggest electric loads in a restaurant or convenience store, and it runs every hour of every day. When its energy use climbs, the extra cost is steady and easy to miss, and the same problems that waste energy usually wear out the compressor faster.

Two things to know up front. First, long run time is normal: Heatcraft designs 35°F coolers for about 16 to 18 hours of compressor run time a day and storage freezers for 18 to 20. Second, the bill tells you something changed, not what. This page helps you find what.

Where a walk-in's energy goes

A walk-in uses electricity in four main places:

• The compressor, which does most of the work. Anything that makes the system run longer or at higher pressure raises its use.
• Fans: evaporator fans inside the box, which often run most of the time, and condenser fans outside.
• Heaters: defrost heaters on freezers, door frame and glass door anti-sweat heaters, drain line heaters and heated relief ports.
• Lighting inside the box and in glass merchandising doors.

What's usually behind a rising bill

Coils

A dirty condenser raises head pressure, and the compressor draws more power for every hour it runs. It's the most common and cheapest energy fix. See condenser coil and condensing unit overheating. Our post on how dirty condenser coils affect performance goes deeper.

Doors, gaskets and strip curtains

Every time warm, moist air gets in, the system has to cool it and then melt the frost it leaves on the coil. A door that doesn't close by itself, a torn gasket or a propped door adds that load all day. Federal efficiency rules for walk-ins made since 2009 require automatic door closers, plus strip doors, spring-hinged doors or another infiltration-reduction method, for exactly this reason. See door gaskets, door won't close and strip curtains.

Heaters that never switch off

Freezer door frames and glass merchandising doors use anti-sweat heaters to stop condensation and ice. Federal rules cap anti-sweat heaters that have no controls at 7.1 watts per square foot of door opening on freezers and 3.0 watts per square foot on coolers. Above those levels, a control has to modulate the heat based on humidity or condensation. A heater control that has failed "on," or was bypassed, runs full heat around the clock. See door frame heaters and glass display doors.

Defrost

Defrost heats the coil on purpose, then the system has to remove that heat again. More defrost than the coil needs is pure waste. Heatcraft's condensing unit manual gives two to four defrost cycles a day as typical for freezers, but the right schedule depends on the box. Demand or adaptive defrost controls can cut unneeded cycles. See defrost system.

Fan motors

Walk-ins made since 2009 must use electronically commutated (ECM) or three-phase motors for evaporator fans under 1 horsepower and under 460 volts. Condenser fan motors under 1 horsepower must be ECM, PSC or three-phase. Older boxes, and boxes repaired with cheaper replacement motors, may still have less efficient motors running all day. When a fan motor fails, replacing it with the right type matters. See evaporator fan motor and DOE rules and repairs.

Lighting

The same federal rules require interior walk-in lighting to deliver at least 40 lumens per watt, or be on a timer or sensor that shuts it off within 15 minutes of the walk-in being empty. Old lamps left on all day add both electricity and heat the system then has to remove. See lights not working for fixture issues.

Low charge

A slow refrigerant leak often shows up on the bill before it shows up as a warm box. The system runs longer to do the same job. Walk-ins holding 15 pounds or more of an HFC refrigerant also fall under EPA's leak repair rule, which requires repair when the leak rate exceeds 20% for commercial refrigeration. See refrigerant leaks and recharging.

Checks staff can do safely

1. Compare like with like. Compare this month's bill with the same month last year, not last month. Summer is always higher.
2. Watch the door. Does it close and seal by itself every time? Is it propped during stocking? Are strip curtains intact and down?
3. Check gaskets. Look for tears and gaps. Close the door on a dollar bill in several spots; if it slides out easily, the seal is weak.
4. Look at the condenser coil. Is it matted with dust, grease or debris? Is the area around it clear?
5. Feel the glass doors (on a beer cave or reach-in wall). Warm glass on a dry day may mean heaters without working control.
6. Check the lights. Are they on when nobody's inside? Do they have a sensor or timer?
7. Log run time or temperature if you have monitoring. A box that recovers slower than it used to is a warning.

What a technician will check

• Condenser and evaporator coil condition and airflow.
• Refrigerant charge, superheat and subcooling, and a leak search if the charge is low.
• Defrost schedule, termination and fail-safe settings.
• Anti-sweat heater controls and settings.
• Fan motor types and condition.
• Door closer, gasket and hinge condition.
• Compressor current against the nameplate.

When it points to replacement

Most energy waste is fixed with cleaning, gaskets, closers, heater controls and correct replacement motors. The bigger decision comes with an old system that's also leaking or on a refrigerant that's getting scarce, or a box with waterlogged panels. The repair or replace guide walks through it, and our walk-in energy efficiency page covers what newer equipment changes. JayComp designs and installs replacement systems, panels and glass doors when that's the better investment.