What size heater do I need?

Above Ground Swimming Pools
Pool dimensions (feet) Volume when filled to 6" below top rim Minimum recommended heater size
Round Pools
UK Gallons / (Litres) kW - kilowatts
12' x 3' 1,761-gal / (7,994-ltr) 4.5-kW
15' x 3' 2,752-gal / (12,494-ltr) 6-kW
15' x 4' 3,854-gal / (17,492-ltr) 9-kW
18' x 4' 5,548-gal / (25,187-ltr) 9-kW
Oval Pools 
L x W x D
UK Gallons / (Litres) kW - kilowatts
16' x 10' x 3' 2,157-gal / (9,792-ltr) 4.5-kW
24' x 12' x 4' 5,605-gal / (25,446-ltr) 9-kW
30' x 15' x 4' 9,592-gal / (43,547-ltr) 15-kW
In Ground Swimming Pools
Pool dimensions (feet) Volume when filled to 6" below top rim Minimum recommended heater size
L x W x D
UK Gallons / (Litres) kW - kilowatts
20' x 10' x 4.5' 4,983-gal / (22,620-ltr) 9-kW
24' x 12' x 4.5' 7,175-gal / (32,573-ltr) 12-kW
30' x 15' x 4.5' 11,211-gal / (50,895-ltr) 18-kW

How long will it take to get my pool to temperature?

If the heater has been correctly sized for the size of the swimming pool and type of pool construction then it should take between 24 and 48 hours of continuous running (i.e. with the red heater on light illuminated throughout this period) to initially get the swimming pool to temperature. 

Heat loss will slow the above times down so during periods of cold average ambient air temperatures it will take slightly longer than indicated above and equally during periods of high average ambient air temperatures the above indicated figures will reduce.

This initial climb from your starting temperature to your finial swimming temperature is the longest and hardest part of the heating process - once the required temperature has been achieved the heater will then only need to match the heat loss of the pool so may only need to come on for a few hours per day to top the pool back up to temperature.

How much will it cost to heat my pool?  

Assuming the cost of a unit of electricity to be 6 pence it will cost £4.32 to heat 1000-gallons (4500-Litres) of water from tap temperature to a reasonable swimming temperature. This equation makes no allowance for heat loss.

For Example: an in-ground 24' x 12' pool with an average depth of 4' holds approximately 7200-gallons. The cost to initially bring the pool to temperature using peak rate electricity will be 7.2 x 4.32 = £31.10 Note that cheap rate electricity is usually billed at less than half the peak rate tariff and could therefore reduce this bill by more than half.

The cost of maintaining the water temperature will be dependant on the level of insulation given by the pool structure, a moderately well insulated pool being used only during summer months may only require 3 hours of top up heat on average per day. At a cost of 27 pence per 1000-gallons (when the heater is sized in the ratio 1.5-kW per 1000-gallons). The religious use of a solar floating cover could dispense with the need for any top up heat being required during warm sunny days.

Please note the above information is for guidance only & running costs will vary from pool to pool and will be dependant on the following main points:

The Level Of Insulation
Average Ambient Air Temperature
Required Water Temperature N.B the greater the gap between the required water temperature and the average ambient air temperature the greater the heat loss that will be experienced.
Wind Chill (If the pool is sheltered from the wind this will also reduce the heat loss dramatically)
The Cost of a Unit of Electricity  

Do I need a solar cover?

A solar cover is an absolute minimum requirement if you wish to heat your swimming pool. Without a solar cover on the pool it can only be likened to trying to heat your house in the middle of winter, without a roof It simply will not happen!

Does insulation make a difference?

The best way of answering this question is with the below case study:

"In my garden I have a 24-ft x 12-ft x 4-ft deep, 6400-gallon oval above ground pool; this was installed in the place of a rather tired 15-ft diameter 4-ft deep 4000-gallon pool. An under ground power cable was originally installed with only enough capacity to supply a 6-kW heater. To upgrade the cable would have meant digging up a patio, and tunnelling under a wall. I thought a 6-kW heater would not be sufficient but in an attempt to rescue the situation, without upgrading the cable, I lined the pool floor and walls with 20mm thick expanded polystyrene sheet (the heavy duty version that will support 10.2 tonnes per square metre)."

"This pool has been in use now for 3 years it is heated to a constant 28ªC from mid April to mid September. During good sunny weather the heater switches off for days on end, if the solar cover is not stripped off on a daily basis the temperature can rise dramatically."

"The running costs of this pool are significantly less than its smaller non-insulated predecessor, with heat up time remaining approximately the same."

The Conclusion Is Simple; 
To Insulate A Pool Pays Dividend Upon Dividend

And will repay the purchase cost of the insulation materials usually within the first season. Allow me to go further and liken it to heating a room in your home in mid winter, leaving the doors and windows open - the house will never reach temperature. Close the 'doors & windows' on your pool (insulate it). Keep that valuable heat where you want it, don't heat the neighbourhood.

Can I plug the heater in?

The largest power output heater that can be plugged in via a standard 3-pin domestic plug is 3-kW (13-Amp). Heaters 4.5-kW and greater will need to be hard wired back to the property's main electricity meter by a qualified electrician, in the same way as an electric cooker or shower would be wired.

What size cable do I need?

As a 'rule of thumb' guide cable section should be calculated at 1mm² conductor for every 5-Amp of current drawn, this is only a general rule for cable runs up to a maximum of 20 meters.
For greater cable runs the installation electrician will have to calculate what the voltage drop will be and increase the conductor size sufficiently.

How long will the heating elements last?

The heating elements used in all Elecro heaters are of superior build quality and if correctly looked after will last for many, many years. The biggest 'threat' to the heating elements is poor water chemistry / water balance, if the water chemistry and water balance guidelines within the installation and operating manual are followed then your heating elements should last upwards of 10-years.

Can I buy directly from you?

Unfortunately we are unable to supply members of the public directly, if you wish to purchase any Elecro product please contact your preferred retailer.

If you already own a Elecro product and require spare parts then we can supply these to you directly, for further information please email your requirement to sales@elecro.co.uk or alternatively call our office on +44 (0)1438 749 474 during our opening times.

Are Elecro heaters suitable for salt water pools?

Elecro heaters with Titanium heating elements are suitable for use with salt water swimming pools. To check which model you have please check the product code on the specification plate or flow tube label. A full list of Elecro product codes can be found on the 'models' tab within the relevant product page.

If you have any queries concerning which model or version you have please email technical@elecro.co.uk

If you have a question that is not answered here please email technical@elecro.co.uk