Go solar with net metering — the compliant way

Net metering is a billing arrangement, not a piece of equipment. You connect a grid-tied renewable system alongside your normal supply, and the surplus your panels send back to the distribution network is credited to your account and set against the electricity you buy later. The Code's own term for you once this is in place is a customer-generator.

The important consequence is in the design brief: net metering is intended to supplement what you buy, not to run a power-selling business — the Renewable Energy (Amendment) Act, 2020 says it is not an income-generating mechanism. So the system gets sized around your own demand, and a system sized to export for profit is the wrong system.

Credits offset the electricity you draw later — at night, or on a cloudy day — so they reduce what you owe rather than paying you cash. They roll over between billing periods, and the arrangement is settled over an annual tracking period, so a surplus built in the bright months can carry into the darker ones.

Two limits worth knowing before you size a system around them. Approved taxes, levies and service charges on the electricity you consume still apply, and credits cannot be used against those. And the scheme assumes that over the year you will not export more than you import — which is another way of saying it is not designed to make you a net seller.

I can't quote a credit rate: the Code sets the mechanism, and the tariff and charges are set separately by the PURC and may be changed periodically.

The Code covers connections to the low-voltage distribution network — nominal voltage below 1 kV — which is where homes, SMEs, commercial premises and public institutions sit. In practice that means customers of ECG, NEDCo and Enclave Power.

To actually get connected, the installation has to meet the Code's technical and safety requirements, which is the part that decides most applications: anti-islanding that ceases to energise within two seconds, a visible and accessible disconnect device, correct earthing, surge protection, and an inverter certified to the relevant IEC and IEEE standards. The utility also has the right to witness commissioning and to keep a copy of the test data.

3ESL handles this as your EPC — design, install, commission and the application itself.

A net-metered system must stop energising the network within two seconds of losing utility voltage. This is anti-islanding protection, and it is not optional — it exists so a lineman working on a supposedly dead line is not killed by your inverter back-feeding it.

Coming back is deliberate too: the grid has to be stable for at least five minutes before the system resynchronises — voltage within 90–110 % of rated and frequency between 49.8 and 50.2 Hz — and on a network with automatic reclosing, the system waits at least five minutes for the recloser to normalise first.

This is the thing people are most often surprised by: a plain grid-tied net-metered system goes off during an outage, along with everything else. If you want power during dumsor you need a hybrid inverter with battery storage and a properly configured backup circuit. That is a different design, and we build both — worth saying which one you actually want early.

The Code draws two lines, both in kVA:

• Above 13.8 kVA, the inverter must be a balanced three-phase type. At or below it, single phase is allowed.
• If you already have a multiphase connection and the generating unit is larger than 4.6 kVA, it has to be split in a balanced way across all the phases.

There is also a note worth flagging early on rural or long-feeder sites: on a long feeder spur the maximum capacity may need the utility's approval, and may force a three-phase connection regardless of what the numbers above allow.

That threshold is one of the first things we check at the site assessment, because it changes the inverter selection and therefore the price.

The inverter has to be certified against the standards the Code names, not merely sold as grid-tied:

• IEC 61727 — performance, including disconnection on loss of grid and DC current injection.
• IEC 62116 — the islanding prevention test. This is the one that proves the two-second rule.
• IEC 62109-1/2 — inverter safety.
• IEC 60364-7-712 — the installation itself, for PV supply systems.
• IEEE 519 — harmonic emission limits.

And there is one requirement people miss because it sits in the power-quality section rather than the inverter section: DC current injected into the AC side must stay below 1 % of the unit's rated output current.

The operating envelope, straight from the Code:

• Frequency — no disconnection is allowed while the system is between 48.75 Hz and 51.25 Hz. That is the continuous-operation band.
• Voltage — continuous operation between 90 % and 110 % of rated voltage; no disconnection is permitted inside that range. Outside it the response times in the Code's Table 1 and Table 3 apply.
• Power factor — unity, or at least 0.98.
• Rapid voltage change — connection and disconnection must not move the voltage at the point of connection by more than 3 %.
• Voltage unbalance — a 2 % compatibility level on LV three-phase networks, or 3 % where single- and two-phase customers predominate.
• Relay tolerance — voltage settings within ±1 %, frequency within ±0.1 %.

Modern certified inverters meet all of this out of the box. It matters at design time because it constrains protection settings, and at commissioning because it is what gets tested.

The parts that most often come up on an inspection:

• A disconnect device at the point of connection or the distribution board — visible, easily accessible to service personnel, and manually operable. Not a setting inside the inverter.
• Surge protection — Type 2 SPDs between the system and the interconnection.
• IP65 enclosures for anything installed outdoors.
• Earthing per the National Electricity Distribution Code, and it must not disturb the network's own ground-fault protection coordination.
• Labelling — signage on the distribution board telling anyone working there to fully disconnect and isolate the generating facility first, and every item of equipment labelled.
• Emergency shutdown — in an emergency, all fuel inputs including the inverter's DC input and all AC voltages must be shut off, whatever mode the equipment is in, and the DC side open-circuited.

The Code is explicit that protecting the facility is the customer-generator's responsibility under all conditions — including when the system is not running.

Commissioning runs after the interconnection is installed and ready, and the utility may attend and take a copy of the test data. The tests the Code lists are:

• verification and inspections;
• production tests — response to abnormal voltage, response to abnormal frequency, and synchronisation;
• the unintentional islanding functionality test;
• the cease-to-energise functionality test.

You or your installer must supply the engineering drawings, schematics and testing certificates for the equipment and protections. The utility can also test the protection relays and controls before final approval — or at any time afterwards.

On our jobs the results go onto an instrument-recorded electrical test record and commissioning report, signed, so the evidence exists later when somebody asks. That is the same discipline whether or not the meter is a net meter.

A bi-directional meter that records import and export energy separately. All meters on the distribution network are the supplier's property even when they sit on your premises, and the supplier is responsible for designing, providing, installing, operating, maintaining, testing and sealing the meter.

So the meter is the utility's part of the job. Ours is everything on your side of it, plus getting the application through.

Ghana's net-metering rollout runs under the Scaling-Up Renewable Energy Programme (SREP), backed by the Government of Ghana with the African Development Bank, the Climate Investment Funds and Switzerland's SECO. Under that national programme, systems below 10 kWp for SMEs and private homes may attract a subsidy, and there is a national online application portal.

I'm deliberately not quoting an amount or a current status — programme terms change, and the subsidy sits outside the Net Metering Code itself, which is the document I answer from. Ask us and we will tell you where it stands this month, and whether your system falls under the threshold.