GSM Limited has been established for over 30 years, based in Newent, Gloucestershire providing professional services to Commercial and Domestic customers. As a customer you are guaranteed that GSM staff will take care of your needs from fully designing systems to planning applications through to installation, commissioning and maintenance programmes. 

We were the first company in the UK to gain accreditation for Heat pumps and Solar PV under the Microgeneration Certification. We take pride on keeping up to date with the best technology and providing the most cutting-edge engineering solutions to our customers. We have a vast range of specialist installers that ensure all technologies are bought together to work in harmony.

What Can We Do?

GSM Ltd have over 30 years’ experience in the renewable energy sector and we have a real wealth of understanding of how to best integrate all the latest technologies so that they work in harmony together to provide the ultimate energy efficient home.

No Sub Contractors

All engineers, surveyors and designers are directly employed by GSM Ltd. From initial survey through to completion and handover we ensure that we are always courteous, tidy and professional in everything we do.


Every year we carry out a servicing schedule to our ever-expanding client base of heat pump installations.

We group the areas by postcode so that we can keep the costs of our serving to a minimum. 

If you should wish to be included within our servicing schedule, then please email us and a member of our team will get straight back to you.

Products We Install

Tesla Powerwall 2

Tesla Solar

At GSM ltd we believe that every household and business self are passionate about energy self sufficiency.  We believe Tesla are the main players in the future of energy production and energy storage  renewable energy. Using the you own generated energy smartly without detriment to the end user comfort. 

Time of Use Tariffs

Across the nation, electricity demand reaches a high in the late weekday afternoons (4-7pm), and then falls to a low overnight. However, to date most domestic properties have paid a single rate electricity tariff which doesn’t reflect the peaks and troughs of demand. Some domestic properties are on an Economy 7 (or Economy 10) tariff with a ‘peak’ rate (15-20p per kWh) and an ‘off-peak’ rate (7-9p per kWh). 

More suppliers are starting to trial or offer time-of-use (ToU) tariffs, with time banded tariffs reflecting demand and supply across the nation and the true ‘underlying cost’ of electricity.

As an example, here is Bulb’s smart tariff for South East England:

Time of Day Cost per kWh

Peak (Weekdays 4-7pm)


Off Peak (Weekdays 7am-4pm and 7pm-11pm, weekends 7am - 11pm)


Overnight (11pm-7am)



With the advent of smart meters, able to record half hourly electricity use, the market will gradually witness the introduction of many more such time-of-use tariffs. Clearly there are large savings (up to 34p per kWh under with Bulb) to be made by buying electricity at night and using it in the day. Time-based Controls are now in place for Powerwall 2.

The system user can choose between three different modes in the Customise tab of the Tesla app. The different modes are summarised below:

  • Self-powered This mode is purely for solar self-consumption, with no charging from the grid. It will prioritise charging from the solar at all times and discharge whenever it can to maximise self-usage.
  • Advanced - Time-based control (Balanced) Balanced mode is the same as self-powered, except you can tell Powerwall the peak and off-peak times for your tariff and the battery will DISCHARGE at peak times in preference to off-peak times to maximise savings. There is still no charging from the grid in this mode.
  • Advanced - Time-based control (Cost Saving) Cost-saving mode incorporates charging from the grid at off-peak times where possible to maximise savings, as well as charging from solar during the day.
Mode Backup Reserve Solar Self Usage %  Savings  Who should do this?
Self-powered  Configurable (0-100%) Great! OK "I want to minimise my carbon footprint"
Advanced - Time-based control (Balanced) Configurable (0-100%) Good Good


"I want to minimise my carbon footprint and I have a ToU tariff"

Advanced - Time-based control (Cost-Saving) Configurable (0-100%) OK Great! "I have a ToU tariff and want to maximise my savings"


You don’t even need a solar system to benefit from time of use charge and discharge. That said, the best savings will be realised through a combination of solar self-consumption and ToU charging and discharging.


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