Big savings with heat pumps

With cash-strapped consumers tightening their belts against the backdrop of rising food, fuel and energy prices, many homeowners are considering installing a heat pump to bolster the functioning of their existing geyser. Today, there are a variety of heat pumps on the market that promise homeowners a reliable water heating source with significant energy savings and as a result, lower electricity bills at the end of the month.

Water heating currently contributes about 40% of your home’s total electricity usage. You could save a fair percentage of your monthly power bill just by retro-fitting a heat pump to your geyser.

Naturally, the heat output of the pumps changes in accordance with the ambient temperature. But even on cool days, the pumps continue to effectively produce heat at a fraction of the cost.

For example, on a mild day, a Cobra Heat Pump uses three times less electricity to produce the same amount of heat generated by a conventional electrical geyser. Cobra Heat Pumps are specifically designed for South African conditions and can successfully operate in ambient temperatures of between -5°C up to 43°C.

Many believe that heat pumps offer an attractive alternative to solar powered water heaters, as they don’t have to be installed on the roof and can be fitted neatly and compactly at the back of your house. Plus, you can install a user-friendly LCD remote display inside your home, along with your Cobra Heat Pump, which provides quick and easy access to a range of information such as the water temperature, running times and system diagnostics to ensure optimal functioning of your heat pump.

Cobra Heat Pumps are designed to heat your water to 55° and for convenience, the water can be heated to 65° using the 2Kw back-up element.

Many heat pumps boast a range of innovative and practical features.

For example, Cobra Heat Pumps have a range of innovative features, such as a steriliser function that automatically sanitises your geyser once a week to prevent the growth of harmful bacteria and viruses.

In the event of any problems with the system, a flick of the unique “cross-over” switch will put you back onto Eskom power until an installer can attend to the possible error.

The pumps can be easily retro-fitted to your existing geyser by a professional plumber.

They can also be used in conjunction with a solar water heater, and depending on the type of installation, you could qualify for an Eskom rebate.

To find out if you qualify, you can contact one of Cobra’s qualified installers who are ready to advise you on possible rebates and the correct size heat pump for your needs, as well as to arrange to professionally install the system for you – simply call 0861 212 121.

Heat pumps come in various sizes – for example, Cobra Heat Pumps are manufactured in two different sizes; a 3.0Kw which is suitable for heating between 100 to 250 litres of water, and a 4.7Kw which is suitable to heat between 200 to 500 litres of water a day. – Antonella Desi

Readers' Comments Have a comment about this article? Email us now.

I am a plumber of over 25 years experience and have installed heat pumps from Cape Town to Maputo.Firstly and most importantly, you need eskom to be producing electricity for a heat pump to work. On a proper thermo siphon solar system the hot water is free. In order for a heat pump to work efficiently, you need a large capacity of stored water, it only heats the water a few degrees as the water passes thru the heat pump, so it needs to make many “passes” to get up to 55 degrees. This is why it they are offering a “back up” to heat the water to 65 deg, with an element, which is what you would have been using anyway, so actually the saving is now not so great... For a very large house or hotel, with a hot water reticulation system and overcapacity hot water storage with very efficient insulation and on a new build, it is defiantly an option to consider but as a retro fit, its marketing hype, they got units to sell. They haven’t even mentioned that the regular servicing on this unit needs to be done by a fridge mechanic and probably a plumber, so there go any savings. It is my opinion that the best and most efficient way of saving money on heating water costs is to install a timer switch to your geyser. The cost of the timer (R 370) and the electricians labour cost (R 400) can be recovered in 2 months, from then the saving is yours. I am saving about R 400 a month on my electricity cost since installing one. It you take the cost of any of the other ways of heating water over the efficiency of the unit, ( 8 months of sunshine) and the lifespan of it (5 to 8 years), not such big savings, actually. - Guy

Heat pumps extract heat from sun-warmed air outside and transfer this to your geyser where it efficiently heats the water to be used in your home. Because the pumps simply move “free” heat from the outside air to the water, rather than generating their own heat, they can heat geyser water for up to 60% less when compared to the cost of traditional heating methods using an electrical geyser -All I say is that for someone who knows zero about a heat pump – you have written a fairly good article. I read the whole thing despite the obvious lack of knowledge. Sorry – it annoys me that your article was published – and its an advert – and no-one edited / proof read – with such an obviously incorrect statement.- Bryne

Check out how very cheap and easily a gas water heater [Junkers or the Chinese replicas] can be fitted to your hot water /shower and bath/ existing system!Now you’re on subsidized, efficient fuel, and out of Eskom’s reach! - Ronald

I find it disturbing that Guy can make comments which will mislead people that are looking for genuine technical information in order to make a choice between Solar water heating or Heat pumps. He may have been plumbing for 25yrs but he is not up to speed with the latest developments. In comments that Bryne made I would like to put him right on a few points. I have installed many solar systems and heat pumps and can comment as follows. 1. If one can afford to install the right size solar water heating system(300L +) I agree that it is probably more economical than using a heat pump. The point is that most families cannot afford to install a large enough system for total daily needs, so the element has to supplement the solar. You can only get one tank of solar hot water during the day which is when most people don’t use it - water usage is in the mornings and evenings. On the days with no solar radiation electrical back–up must be used. 2. A heat pump will operate 24/7 giving savings of 66% compared to element heating with an ambient temperature of 25C and the efficiency increases with temperature. Bryne is correct in saying that the heat pump can only heat water up a few degrees at a time (5C for each pass through the heat pump) and most brands have a problem with cool water mixing with the hot when the heat pump switches on. “ITS solar” have developed and patented a method of delivering water to the geyser only when it reaches 55C, so that there is no mixing of the cooler water with the hot water in the geyser. 3.In high water usage situations a heat pump can be used much more effectively. A 3Kw heat pump if in use for 12 hours could deliver ± 900L of water using 12 x 850 watts of power in so doing which equates to 10.2units of electricity. I would summarise as follows: In a domestic situation up to 5/6 people with average usage of hot water at 70L per person per day, a system(s) of total capacity of 350/400L would be required to avoid using the back- up element. At current pricing of good quality solar systems this option would cost about R40,000 (2 x 200L systems). A house with two existing geysers of 150L or 200L which are not too far apart could be served by one 4.7Kw heat pump at a cost of about R13,000 including re-plumbing of the two geysers, installation and compliance certificates. The equation is very much in favour of the heat pump. The running cost of the heat pump is so small that over a period of a year the actual electrical consumption of the heat pump versus the average solar system equipped with a back–up element is very similar. - Tony

My major point – and problem was that the original article says that the way a heat pump works is to “extract heat from the air which has been warmed by the sun” I had simply cut and paste your paragraph – intending to highlight it. No! a HEAT PUMP WORKS BY COMPRESSING ( usually a gas – in a closed circuit) – WHICH CAUSES IT TO HEAT UP. Basic physics. This hot gas is then used to heat up the water n a “Heat Exchanger”. Tony makes good points – and at least backs it up with facts and science. All he needs to do now is to draw up a table so that variables may be inserted to enable one to make a intelligent decisions. Thanks Tony. - Bryne

The article is an advert yes, for the principal of using heat pumps. Cobra is mentioned ...so what, they probably made an advertising contribution? All the comments have some merit except that from Bryn who seems not to appreciate the principals at all. Air at all temperatures, altitude (pressure), and relative humidity contains heat of a known amount per unit volume(say M³); and yes the air got it’s heat from the sun! A heat pump is basically an air conditioning unit in principle but in reverse, atmospheric air being used to extract some of its heat instead of as a means to reject heat to atmosphere. The compressor taking gas to a liquid state causing the heat that we need to work with is just not so. That’s just an unfortunate ” loss”, although some more sophisticated units use this waste heat for other purposes. The compressed gas (now liquid) is used in the transfer of the heat from and to the air exchange units (like car radiators). The liquid holds more heat than the gas so the liquid is “Expanded” in the outdoor unit to give up its heat and this is disposed of via the outside heat exchanger. Wait a minute…don’t we have air conditioners now that cool or heat on demand??? Well say no more, just look it up on the Internet if you don’t follow the principal. - Terry