Savings from solar hot water

Solar water heating is one of the most efficient renewable technologies available. The payback time now makes solar water heating financially as well as environmentally viable for the majority of domestic and commercial projects.

In order to calculate the financial savings it is important to understand the costs of running a conventional heating system and make some assumptions about future energy costs. The typical output of one of our systems is provided to you in the table below.

The first factor to consider is the type of fuel and equipment you use to heat your hot water at present; from that we can estimate the efficiency of the existing system.

A working boiler only reaches its maximum efficiency once it has been running continually for a period of time (typically 5-10 minutes), this is simply down to the inefficient burning of fuel.

Electricity is 100% efficient in delivering energy into water so there are no delivery losses.

A new condensing boiler may be 95%+ efficient in winter (due to long cycle times) but efficiency in summer can fall to 40% (due to short cycle times).

Non-condensing boilers may be as little as 30% efficient in winter and 5% efficient in summer due to short cycle times.

Combination boilers are inherently inefficient at heating domestic hot water because the cycle is only for the length of time that you run the hot tap.

Other areas of energy loss are from old poorly insulated hot water cylinders and pipe work; how long does your hot water stay hot in the cylinder?

Hot water cylinders are often replaced as a part of our installation. The cylinders should have at least 60mm of rockwool insulation and all pipes should be insulated.

As a result of these inefficiencies the price you pay for 1kWh of gas to your utility company is the cost for the energy your system uses but not what you receive as useable heat. In most cases the 1kWh of energy that is used by you often results in less than 0.4kWh in usable energy.

It is reasonable to assume that if you are paying 3p per kWh for gas to your utility company the true cost of the kWh you receive as hot water at your tap is 7p per kWh or more.

Energy and fuel prices have risen dramatically over the last few years and we believe that are likely to continue to do so in the future.

A single panel domestic solar water heating systems will deliver up to 2,000 kWh per year to your taps with little or no running or maintenance costs.