Solar Power for Telecom Towers: Cutting Diesel on Off-Grid and Bad-Grid Sites

A telecom tower site has an unforgiving brief. It must be powered every hour of every day, nobody works there, and on a large share of sites in Africa there is either no grid or a grid that cannot be relied on. For decades the default answer has been a diesel generator, often two, with a battery bank to ride through the gaps. It works, and it is expensive in ways that do not all appear on the fuel invoice.

Solar with battery storage has been cutting diesel on tower sites for years, and the technology is no longer the hard part. The hard parts are knowing the real load, choosing an architecture that suits the site's power system, keeping hundreds of dispersed sites secure and maintained, and agreeing who pays for the change and who keeps the saving.

Why Tower Sites Burn Diesel

Sites fall into two groups. Off-grid sites have no utility connection, so a generator or a renewable system supplies everything. Bad-grid sites have a connection that delivers power for part of the day, at unpredictable times or voltages, and a generator fills the rest. The GSMA's work on renewable energy for mobile towers notes that many towers in these off-grid and bad-grid areas still rely on diesel, and that 88 percent of such sites continue to be powered by non-renewable sources.

The cost of that diesel has several parts.

Run hours. A generator that carries the site continuously runs every hour of the year. Every one of those hours burns fuel and brings the next oil change, filter change and overhaul closer.

Light loading. Tower sites are commonly served by generators far larger than the load, chosen for starting surges, future tenants or simply what was in stock. A diesel set running at a small fraction of its rating burns more fuel per kWh than one near its design load, and suffers wet stacking and carbon build-up over time.

Fuel logistics. Fuel has to be trucked to every site, often over poor roads, sometimes through insecure areas, and in the rainy season sometimes not at all. The delivery cost per litre at a remote site can be a large addition to the pump price.

Fuel theft. Diesel is valuable and easy to sell. Pilferage from tanks and during delivery is a persistent loss across the industry.

Maintenance visits. Every service is a vehicle, a technician and a day. Across a network of dispersed sites, the visit count is a cost in its own right.

The broader economics of solar against diesel are set out in our comparison of solar and diesel generators in Nigeria. On a tower site the case is usually stronger than on a commercial building, because the load runs through the night and the fuel has to travel so much further.

Where the diesel cost of an off-grid or bad-grid tower site comes from. Only part of it appears on the fuel invoice. Source: MIMAH engineering practice; share of non-renewable sites from the GSMA ClimateTech programme.

What the Site Load Looks Like

A tower site's load is fairly flat and runs 24 hours a day. There is no evening peak worth the name and no weekend dip, which makes it unusually predictable once it has been measured. Measured is the word that matters. Typical loads are a few kilowatts, but the range between sites is wide, and a design built on a network average or on equipment nameplates will be wrong for many individual sites.

What drives the load is well understood.

Tenants. A tower that hosts several operators carries several sets of radio and transmission equipment. Each new tenant adds load, and a design with no allowance for growth is obsolete at the next lease.

Technologies. Every additional radio technology and frequency band on the site adds radio units, and traffic affects how hard they work.

Transmission. Microwave links and their equipment add a steady load of their own.

Cooling. Often the largest variable. Equipment in an indoor shelter with air conditioning draws far more cooling power than equipment in outdoor cabinets with fans or heat exchangers, and in a hot climate the difference can dominate the site's energy use. Moving from shelter to outdoor equipment is frequently the cheapest energy saving available, before any solar is installed.

The right starting point is a logging measurement of the DC load and the AC load separately, over at least a week and preferably across seasons. Rectifier controllers often record DC load already. The generator and grid meters show the rest.

The -48 V DC Power System

Telecom equipment runs on DC, conventionally at a nominal -48 V. The European standard for the power interface at the input of ICT equipment, ETSI EN 300 132-2, defines a normal service voltage range of -40.5 V to -57.0 V at that interface.

The DC power system on a typical site has three parts. Rectifiers convert AC from the grid or the generator into -48 V DC. Batteries sit on the DC bus, floating at full charge and taking over instantly when the rectifiers stop. Distribution feeds the radio and transmission equipment through fuses or breakers. AC loads, such as shelter air conditioning and lighting, are supplied from the AC side.

That architecture suits solar well. Solar charge controllers, DC to DC converters with maximum power point tracking, can feed the array's output straight onto the -48 V bus, and the ETSI standard itself names DC to DC converters on a solar system as a source for this interface. A DC-coupled design avoids converting solar power to AC and back again through the rectifiers, which saves conversion losses and equipment. Where there is a large AC load, typically air conditioning, an inverter or an AC-coupled design may still be needed, and that is another argument for reducing the cooling load first.

Architecture Options

Generator and battery cycling. The simplest step away from continuous running. The generator runs at a healthy load to carry the site and charge the battery, then stops while the battery carries the site. No solar at all, and still a large cut in run hours.

Solar, battery and generator hybrid. The common target for off-grid sites. Solar carries the site by day and charges the battery, the battery carries the night, and the generator starts only when the battery reaches a set state of charge after poor solar days. The generator becomes a backup rather than the primary source.

Solar and battery only. Possible on low-load sites with good irradiance, with enough array and battery to cover the worst weather expected. Removing the generator entirely removes the last line of defence, so the margin must be real and the monitoring good.

Bad-grid sites. Grid, battery and solar together, with the battery sized to cover the outages the grid actually delivers. The generator may be kept for long outages or removed where the records justify it.

A DC-coupled hybrid tower site. Solar feeds the -48 V bus directly through DC to DC charge controllers, avoiding a round trip through AC and the rectifiers. Source: MIMAH engineering practice; voltage range from ETSI EN 300 132-2.

Sizing Logic

The daily energy requirement starts from the measured average DC load multiplied by 24 hours, plus the AC loads and the conversion losses between the source and the equipment.

The solar array is sized to meet that daily energy in the poorest month the design has to cover, after derating for high cell temperature and for dust, and with enough surplus to recharge the battery after a poor day. An array sized for an average day leaves the generator doing the work in exactly the months it was supposed to rest.

The battery is sized for autonomy: the hours or days the site must run with no solar and no generator. On a hybrid site it also cycles every day, so cycle life at the design depth of discharge matters as much as capacity. Daily deep cycling in a hot equipment shelter is hard on lead-acid, which is why lithium iron phosphate is increasingly specified for cycling duty on tower sites. IEC 62619, the safety standard for industrial lithium batteries, names telecom among its stationary applications. Our guide to commercial battery storage covers the kW and kWh sizing and the warranty conditions in more depth.

The generator is sized to carry the site and charge the battery at a controlled rate at the same time. Its start and stop points are set by battery state of charge, with a minimum run time so it is not started for a few minutes and stopped cold. Where an oversized existing generator is being kept, its light loading becomes less of a problem once it only runs to charge the battery at a healthy load.

Remote Monitoring

A network of tower sites cannot be managed by visiting them. The monitoring system is how the owner knows what each site is doing, and it is also how a hybrid system proves its savings.

Fuel level. Continuous tank level readings show consumption and expose theft as a sudden drop that no run hours explain.

Generator run hours and starts. The direct measure of whether the hybrid is doing its job, and the trigger for condition-based servicing.

Battery state of charge, voltage and temperature. Early warning of a failing bank, a charging fault or a shelter that is running too hot.

Rectifier and solar charger alarms. Failed modules, low array output that suggests soiling or damage, and DC bus voltage events.

Site access. Door alarms and, where fitted, cameras, correlated with visits that were actually scheduled.

The data has to reach a network operations centre that acts on it. Our guide to solar monitoring systems covers what good monitoring records and how to set alarm thresholds that people do not learn to ignore.

What remote monitoring should report from every hybrid tower site. It is how the owner manages sites without visiting them, and how the hybrid proves its savings. Source: MIMAH engineering practice.

Security and Anti-Theft

Solar modules and batteries attract theft as surely as diesel does. Anti-theft fasteners, modules mounted high on the shelter roof or on raised frames, welded or tamper-resistant mounting, locked battery cabinets and secure perimeter fencing all raise the effort needed. Some lithium batteries for telecom duty include software locks that make them useless once removed from their own site. Community relations matter as much as hardware: a site that nearby residents regard as their own is harder to rob.

O&M Across Dispersed Sites

A hybrid site needs fewer visits than a diesel site, but the visits it gets have to count. Combine generator servicing, module cleaning, battery checks and a thermal inspection of DC connections into one scheduled visit, carry the spares that the monitoring suggests will be needed, and use the data to move from calendar servicing towards servicing on run hours and condition. Dust matters: an array that loses output to soiling pushes the generator back into service, and the fuel cost of that shows up long before anyone reads a cleaning report. Our solar O&M contract guide covers how to write those obligations into an agreement.

Multi-site programmes are a logistics problem as much as an engineering one. In 2025 MIMAH installed about 1.39 MW of solar across 110 sites in Sudan, in systems of 7.5 to 50 kW, and the lessons carry over directly: standardise the designs, the spares and the commissioning records, and plan routes rather than sites.

Commercial Models

Operator-owned sites. The mobile operator owns the tower and its power system, pays for the conversion, and keeps the fuel saving.

Tower companies. Independent tower companies lease space to several operators and often supply power as part of the lease. The tower company carries the energy cost, so it has the strongest direct incentive to cut diesel.

Energy as a service. An energy service company installs and owns the solar, battery and controls, and charges the site owner a fee per kWh or per month. The site owner avoids the capital cost; the service company carries the performance risk and must be able to maintain what it owns.

Towers as anchor loads. A tower's steady, creditworthy demand can anchor a small power system that also supplies the surrounding community, which is how some mini-grid projects reach viability.

MIMAH's renewable energy team works in telecom as one of its key sectors, designing off-grid and hybrid systems with battery storage and remote monitoring, and maintaining them afterwards. If you are planning a site conversion programme or want a hybrid design checked against measured load, get in touch.