How Much Energy Does It Use?

Dehumidifier Running Costs:

What are the Challenges?

For every luxury and classic car owners and collectors, understanding dehumidifier running costs are important if you are serious about protecting your cars’ which ultimately reduce the cost of care and repair.

But why consider one in the first place? As a classic and luxury car owner, you already know that your vehicle and moisture don’t mix well. But simply wiping your car down in your garage after it’s been out in wet conditions is far from enough to protect your car.

The air surrounding and inside of your car will contain a level of moisture. The amount of water the air is holding, relative to its capacity, is reflected in a percentage. This is called the Relative Humidity (RH).

The presence of moisture in the air isn’t automatically a bad thing. In fact, for things such as leather interiors, the RH to sit above 30% to stop it from drying out and cracking. On the flip side, however, an RH above 65% will encourage mould to grow. Humidity problems extend to other parts of your car, too- iron begins to rust at 50%RH while steel will begin to rust at 80%RH.

As a car owner in the UK, this isn’t good news as we have one of the highest global average RH, sitting at 80%. In warm weather, the air can hold much higher quantities of water around your car, while in cooler weather, the moisture will condense on your car, exacerbating the risk of things like rust, damp and mould. However, there are solutions out there to keep your car safe and protected.

garage dehumidifier how it works

Dehumidifier Running Costs Calulator

For the purpose of the comparison and in an attempt to make the comparison fair, we have used the average weather conditions in the UK, and these are 14oC and 80%RH which is a moisture content of 7.98g/kg.

The design of each selection is to maintain the optimal design conditions for the vehicle of 40%RH within the garage to ensure the vehicle is fully protected. For the comparison, we have used an average 4 car garage measuring 6m x 12m with a standard brick construction and tiled roof.

References for design calculations are:

  • Heating
  • Domestic Dehumidifier
  • Ventilation
  • Infrared
  • Air Conditioner
  • Car Cover

Heating a building is something we have seen attempted in order to increase the air’s capacity to hold moisture which in turn will reduce the RH within the air and the garage. To take air at 14oC and 80%RH, we would have to heat the internals of the garage to 25oC. To achieve the design of 40%RH when its 14oC outside, you would have to heat your garage to 25oC inside. Everything above 14oC outside would mean your garage is getting hotter and hotter. That’s quite a warm car. However, for fairness, the following calculations are used so we can calculate just how much energy is required to achieve the conditions.

The heat energy required to heat a building is required to overcome the losses through the following areas:

    • Air Infiltration (AI) (natural leaking of the building through gaps and cracks.)
    • Heat transmission (HT) through building materials, heat loss based on the U value of the materials.
    • AI using standard CIBSE guides the air infiltration rate for a building of this size would be 0.5ACH, and this equates to 133.2m3/h.
    • HT would be using 2w/m2K for the walls, 6.8w/m2K for the garage door and 2.8w/m2K for the roof.

Based on this the heat loss and energy requirements to heat the building when its 14oC outside and 25oC inside, you would need: 6.037kw of heat required per hour.

A refrigeration type dehumidifier (most domestic dehumidifier) relies on its ability to cool and condense moisture from the air using a cold surface. The limitation of refrigeration in this application is the lowest temperature the refrigeration coil can achieve, this being about 6oC. Due to this fact, in order to maintain 40%RH within the garage using refrigeration, you would also need to heat the space at the same time. To maintain 40%RH in the garage the area its self would have to be kept above 20oC year-round with the addition of refrigeration so not only are you trying to remove the moisture but you are also required to heat the space.

Again we are designing to 14oC outside and 80%RH. This design and energy calculation for this would require both a heating calculation and running of a refrigeration dehumidification unit. This would be as follows:

The heat energy required to heat a building is required to overcome the losses through the following areas:

  • Air Infiltration (AI), natural leaking of the building through gaps and cracks.
  • Heat transmission (HT) through building materials, heat loss based on the U value of the materials
  • AI using standard CIBSE guides the air infiltration rate for a building of this size would be 0.5ACH and this equates to 133.2m3/h.
  • HT would be using 2w/m2K for the walls, 6.8w/m2K for the garage door and 2.8w/m2K for the roof.

Based on this the heat loss and energy requirements to heat the building when its 14oC outside and you need 20oC Inside would be: 3.293kw of heat required per hour

The calculation of the volume of water required to remove from the air is:
266.4m3 volume x 1.2 (density of the air) x 0.5 (Air change rate) x (7.98g/kg – 6.01g/kg)
1000
= 0.314kg/h

The refrigeration unit required to remove 0.314kg/h of water from the air held at 20oC and 40%RH would require 1.58kw of cooling capacity.

The total energy required to maintain the space at 40%RH would be: 4.877kw.

Ventilation is something we commonly hear car owners are using to combat the effects of RH because it doesn’t cost anything. But while ventilation may help dry your car more efficiently, if you’ve put it away wet, bringing in air from the outside only introduces the moisture in that air into your environment. With the UK’s average RH being so high, ventilation is not an effective solution. From this, we would deduce that your ongoing running costs and upkeep cost would be the same as if you had no solution in place at all.

Classic and luxury car owners are usually more aware of the issues relating to humidity and will want to monitor their environment to ensure it’s suitable for there vehicles. An infrared thermometer is a handheld device that can provide an RH reading, allowing you to understand the conditions of your car garage. However, the thermometer only gives you the information instead of providing an actual solution. Additionally, the thermometer requires someone to operate it for a single reading, and so the RH is not continuously monitored. Therefore, your ongoing running costs and upkeep is the same as if you had no solution at all.

Air conditioners are another that commonly get cited as a potential solution. We know that air conditioners cool their surroundings, and so by default, the capacity of the air to hold moisture is reduced. Air conditioners also have a coil inside that’s designed to condense the water vapour into drainable liquid. However, removing water from the air without knowing the RH reading could result in your environment being too dry for leather interiors. Not only that, but most systems can’t effectively tackle the kind of high humidity we experience in the UK, thereby giving you the same struggles as a heating solution.

Car covers are popular, as there’s just a one-off payment. Covers are a great option for keeping dust and dirt off your car, as well as protecting the paintwork from UV rays while it’s sitting outside, but that’s far as it goes. In terms of dealing with relative humidity and actually protecting your car, it’s completely ineffective- in fact, a car cover could do more damage if the moisture condenses on it, leading to rusting and paint damage on the car.

You will be leaving yourself exposed to avoidable ongoing upkeep costs. In fairness, your total ongoing costs are relative to the number of cars you own and their value, but we can surmise that using just a car cover alone, you're ongoing costs to protect them can be valued at: Infinite.

Dehumidification with a Protect by Dehum unit

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Let's compare

With dehumidification, you are dealing with the problem at the source, high humidity is simply too much moisture in the air which is causing corrosion on the vehicle.

As our unique Dehum technology uses a desiccant rotor this is unaffected by temperature as well and can remove moisture at any condition, even down at -40oC. Because of this, the equipment focuses on what’s important for the protection of your car, there is no requirement to heat the building so we simply remove the water from the air.

The calculation of the volume of water require to remove from the air is:

266.4m3 volume x 1.2 (density of the air) x 0.5 (Air change rate) x (7.98g/kg – 3.96g/kg)
1000
= 0.642kg/h

The control of the humidity using a desiccant unit is done through absorption, as the air passes through the desiccant rotor the moisture is absorbed into the rotor and then vented to atmosphere. As the humidity is controlled in this way this means you will only ever use the required energy to remove the moisture from the air.

The unit required to hold the garage at 40%RH year-round is the AD300 and this has an installed power requirement of just 1.51kw. As the unit is controlled by our central control unit as well the unit will only ever use the energy required to keep your car protected. As you can see, it’s significantly lower than other options on the market.

The Summary

How Much Money Can You Save?

As we know, there are different approaches people use to protect the long term life of a vehicle. The only affective approach is to maintain environmental control of 40%RH to stop corrosion in its tracks and protect the vehicle indefinitely. When you are the one paying the running cost bill its important to get this right. Based on the three typical approaches on one clearly gives the results required and it’s also the most energy efficient.

The Results Are In ...

  • Heating the garage: 6.037kw
  • Refrigeration dehumidification: 4.877kw
  • Protect by Dehum solution: 1.51kw

 

Based on the system running all year round and the cost of electricity being 12p per kw the Protect by Dehum solution could save you up £4,745.74 on your annual electricity bill.

How Do you benefit?

Compared to the other ‘solutions’ on offer, non beat the desiccant dehumidifier in terms of dealing with relative humidity. 

  • Low running costs
  • Low-impact
  • Adaptable to your specifications
  • Less spent on car repairs
  • Can switch itself on and off based on the RH reading
  • Quiet
  • Energy efficient

 

Overall, a bespoke desiccant dehumidifier is the best all-round solution to protect your car from the adverse effects of humidity & keeping your running costs down. It deals with the problem at the source and gives you the control and visibility over your car’s conditions to know it’s always being kept in tip-top condition, removing the need for additional upkeep costs- something the other options cannot guarantee.

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