Alright then, let’s have some deep discussion on this.
The first step is to identify and calculate your capacity requirements based on the number of people using the hot water on a daily basis. Are you a Residential or Commercial user?
If you have 6 bathrooms in total, with 3 rain showers, a bathtub in bathroom for children and a normal shower in the parents’ and guest bathrooms, then your demand would be;
- 30 Liters Per Person Per Day for Normal Shower
- 40 Liters Per Person Per Day for Rain Shower
- If your children use the bathtub on holidays, then it would be 100 Liters for your 200 Liter bathtub, since the bathtub is never filled to the brim else the water spills out the moment someone steps in it.
Further, we factor in the design capacity, which is like the car mileage in layman’s terms. While the company may claim greater mileage, the actual use may reveal different results. Similarly, companies profess high flow rate taking into account the high pressure of water at about 4-5 bars, whereas normally, the human body can’t withstand a pressure of more than 2 bars.
Other factors such as comfort, time spent in shower and supply of water should also be considered. While a rain shower mixes scores more on the comfort scale with the air mixing with water, more water flows when taking a shower, which cuts down the time spent in shower drastically. Therefore, if you spend, say 5-6 minutes in a normal shower, you’ll probably take only 2-3 minutes in the rain shower. This will reduce your overall water consumption.
Now, before returning to calculations, an important question to consider is do you want to go for centralized hot water system or are you planning to install at point of usage. Do you want 24 hours running hot water? If yes, then go for centralized water heater with recirculation line as this will provide you the desired comfort.
What is a recirculation line?
You must have noticed that when you open the hot water tap, it takes a while before cold water gets replaced by hot water. This happens because the hot water in your pipeline has lost its heat due to the low ambient temperature. Normally, insulating the pipes helps us in reducing the temperature drop and keeps the line warm to an extent, however, it would not prevent water turning cold over long periods of non – usage. In order to prevent this, a recirculation line may be installed. This consists of an additional line connecting the very last point of hot water pipeline in your house and re-circulating it with the aid of an extremely small pump, which consumes less electricity than a bulb. It essentially keeps hot water running in the pipeline such that it is just enough to ensure the water is always warm in your pipes.
Let’s continue with the calculation part.
For a family of 6, your parents, two kids, your spouse and you, you’ll need,
||No. of liters per person
||No. of people
||Used on holidays
This water would not be consumed at once. In the mornings, you’ll probably consume this water over 2 hours, and your kids won’t be using the bathtub in morning hours on weekdays. This implies you would have sufficient recovery time for the water to warm up whenever the kids wish to use it on holidays or weekends. Therefore, the actual peak usage is approximately 380 liters over 2 hours in the morning, which roughly translates to 170 liters per hour.
Now, that you know what capacity heater you’re looking for, the next question is what kind of heaters are you going for. Still confused? We’ll break it down for you. Would you prefer an Instant or Storage type water heater?
Instant water heater is ideal for small spaces or when you want to use your space economically. Other factors to consider are whether you have high flow shower fixtures or ceiling height available to put in your water heater. While wall mounted water heaters are available in an array of colour options and could be matched with your aesthetics, if you don’t like bulky protrusion on your walls, you can go for instant or centralized water heaters. I would suggest you go for centralized water heater with a capacity of 300 liters although we had calculated the capacity as 170 liters.
However, the next question you'd ask why should you not go for Instant. Let's say you wish to draw out entire hot water I one go, then the maximum you would be able to withdraw is in the range of 60% to 80%, because the moment you will start drawing hot water, cold water will start mixing in it and thus reducing your hot water temperature. Therefore, we need a certain amount of buffer to overcome that dropping of hot water temperature.
If you opt the Electrical Instant, then in order to meet your requirement, with quite a high possibility that two rain showers may operate simultaneously, then you may need approximately
30 liters per minute of flow, which translates to an energy input of 80 KW, a highly impractical scenario.
On the other hand, Instant may work for you if your city does not have severe winters and you do not have any rain showers, then your demand of hot water in terms of liters per min would not be very high. In this case, an Instant water heater available off the shelf in market may be sufficient for your needs.
And that is how capacity plays a key role in determining what water heater systems you go with. Other than electric option, we have solar, gas and heat pump alternatives in water heater systems.
Solar energy is literally free of cost. However, it is not an instant source of energy since it takes time to harness this energy and there would be certain days when the Sun would be missing altogether. For those days, you need a backup. If you have piped gas available in your area then you may go for Solar with gas backup, since piped gas is the cheapest as far as running costs are concerned. If gas is not available, then you can go for Solar with electrical backup.
However, please note that solar would not be efficient if you undersize or oversize your system by even one step! The calculation of hot water demand per hour are replaced by hot water demand in liters per day since that is the time required for Solar water heater to heat up the entire content of water.
Through the above calculations, I would recommend 450 liters capacity of Solar water heater. 380 liters is your actual demand, minus 60 liters required for guest room since it would not be occupied regularly, which comes out to be 320 Liters. The balance 130 liters acts as a cushion.
Gas water heater is also an economical option. With no adverse characteristics, Gas water heaters are much more faster in hot water recovery and cheaper in terms of running costs. They are also much more environmentally friendly. Unlike solar, you are actually burning or using up certain fossil fuel, but you are reducing the overall impact on environment and you would also be saving on your energy consumption bills. The only precaution is that sizing needs to be precise and properly calculated so that you are in position to recover your investment.
As far as recovery of your investments is concerned, there is no fixed formula to calculate it. However, the gas fired water heater costs almost 24 to 30 paise to produce 1 liter of hot water whereas the electrical water heater consumes approximately 55-65 paise for 1 liter. On the other hand, solar is free, but there is investment cost which need to be taken care of. We're sure you can calculate that with you keen financial eye on household budgets among other things.
You might say that it depends on usage as well. The higher the usage, the more the recovery. Yes and No. No, because then in higher usage you will have to increase the capacity of the Solar water heater hence higher investment. Yes, because that incremental investment would be lesser and lesser per 50 Liter of Solar hot water capacity.
Heat Pump is even more energy friendly than Solar, however, maintenance is a huge issue. There aren’t many technicians available for this technology. Although the manufacturers say that even a normal air-conditioning guy can repair it, that doesn’t sound logical since the air-conditioning technician knows the ins and outs of summer cooling, but he doesn’t know anything about hot water system and its functioning. He may repair the heat pump, but he can’t understand the hot water system as a whole, so let’s say you call him up and say that I am not getting sufficient amount of hot water in my bathroom. He might reply that Heat Pump is working, but he has no idea why you are not getting hot water!
Well now you know what you have to do with your house. First of all you would choose your fixtures, and then you will decide on the hot water system. It’s such a simplistic topic, and yet there is acute dearth of professionals in this industry (Hot Water).
Next, we shall discuss the various heating technologies available to you for residential purpose.
Fury Electric / Point-of-use
High pressure, glass lined, for centralised operation, with recirculation pump, made in America, Rheem floor mounted, electrical water heater.
Paloma Gas Water Heater
Highly energy efficient, smaller than EPABX, capable of running rain showers at ease, can fill up entire bath tub/jacuzzi in one go, high pressure, software run, remote controlled, made in Japan, instant gas water heater.
Residential Solar Water Heater
Active split system, tanks could be placed anywhere/hidden, no visible bulky tanks, high pressure, high storage, glass lined, for centralised operation, with recirculation pump, electrical or gas backup solar water heater.
Residential Heat Pump
High pressure, glass lined, for centralised operation, with recirculation pump, made in America, Rheem floor mounted, heat pump with electrical backup.
Similarly, various heating technologies are available to you for commercial purpose.
Commercial Heavy Duty (9KW - 54 KW)
High pressure, high storage, extremely high recovery, software operated for troubleshooting, glass lined, for centralised operation, with recirculation pump, made in USA, Rheem floor mounted, electrical water heater.
Commercial Gas Heater
High pressure, high storage, extremely high recovery, software operated for troubleshooting, glass lined, for centralised operation, with recirculation pump, made in USA, Rheem universal floor mounted, gas water heater.
Commercial Solar Water Heater
Active split system, high recovery, high pressure, high storage, glass lined, for centralised operation, with recirculation pump, electrical or gas backup solar water heater.
Commercial Heat Pump
Commercial heat pump water heaters are ideal in situations such as a commercial kitchen or laundry where there is a steady simultaneous need for cool air and hot water.