The Eco4990ES solar inverter has a maximum continuous AC output of 4.99 kilovolt-amps (kVA), which is the same as 4.99 kilowatts (kW) at unity power factor. This figure is confirmed by the manufacturer’s technical specification, which is registered with the Microgeneration Certification Scheme (MCS). The MCS database lists the inverter under product number Eco4990ES with a rated AC power of 4.99 kVA (MCS Certified, 2026).
- Eco4990ES has a maximum continuous AC output of 4.99 kVA.
- This rating matches 4.99 kW at unity power factor.
- Pair it with up to 6.5 kWp solar array for UK homes.
The kVA rating of the Eco4990ES applies to most standard single-phase domestic solar installations in the UK. The inverter is built to pair with a solar array of up to approximately 6.5 kWp, depending on the panel configuration and local grid connection limits. However, if your home has a three-phase electrical supply, the inverter may need to be derated or a different model selected. The 4.99 kVA output is also the key figure used when applying for the Smart Export Guarantee (SEG) tariff, as it determines the maximum export capacity you can register with your energy supplier.
What the 4.99 kVA Rating Means for Your System
The 4.99 kVA rating indicates the maximum amount of alternating current (AC) power the inverter can deliver continuously. For a typical UK home, this is enough to power most daytime loads, such as a fridge, washing machine, and lighting, while exporting any surplus to the grid. The Energy Saving Trust notes that a 4 kWp solar system can generate around 3,400 kWh per year in southern England (Energy Saving Trust, 2026). The Eco4990ES inverter can handle this output without clipping, as its 4.99 kVA capacity exceeds the typical peak generation of a 4 kWp array.
How the kVA Rating Affects Grant Eligibility
Government grants, such as the Smart Export Guarantee, require the inverter to be MCS certified, which the Eco4990ES is. The 4.99 kVA rating also falls within the typical limit for domestic installations under the SEG, which caps export capacity at 5 MW per site (Ofgem, 2026). This means you can register for SEG payments without needing additional approvals. For the Boiler Upgrade Scheme, the inverter size does not directly affect eligibility, but the system must be installed by an MCS-certified installer.
Checking Your Inverter’s Exact Rating
To confirm the kVA rating for your specific unit, check the product label on the side of the inverter. It will list the rated AC power in both kVA and kW. If you have lost the label, the MCS product database provides the official specification (MCS Certified, 2026). Always match this rating with your solar panel array size to avoid inverter oversizing or undersizing, as incorrect pairing can reduce efficiency and void warranty terms.
A worked example
A typical 1930s semi-detached home in Manchester with a 4.2 kWp solar array paired with the Eco4990ES inverter would cost around £6,500 fully installed under current 0% VAT rates. The Energy Saving Trust estimates this system could save a household approximately £570 per year on electricity bills through self-consumption and Smart Export Guarantee payments. With the ECO4 scheme or a £7,500 BUS grant for eligible low-income homes, upfront costs could fall to near zero. The payback period on the full £6,500 investment is roughly 11 years, with the inverter and panels lasting 25 years. Over that lifetime, total savings including SEG income could exceed £14,000, assuming Ofgem’s typical export rate of 15p per kWh. The system’s 4.99 kVA output comfortably covers daytime loads like a fridge, washing machine, and LED lighting while exporting surplus to the grid.
| Item | Figure |
|---|---|
| Upfront cost after grants | £6,500 |
| Yearly savings | £570 |
| Payback period | 11 years |
| 25-year lifetime savings | £14,250 |
What homeowners often get wrong
The most common mistake is assuming the 4.99 kVA rating means the inverter can handle any solar array size up to 5 kWp. Here are three frequent errors to avoid.
- Matching array size to kVA exactly Many homeowners think the solar panel array must not exceed 4.99 kWp. The right answer is that the Eco4990ES can safely pair with up to 6.5 kWp of panels, giving you more generation in low light without clipping output on sunny days, missing this could limit your system’s annual yield by up to 15%.
- Ignoring the unity power factor rule Some assume the kVA and kW ratings are always the same. The correct understanding is that 4.99 kVA equals 4.99 kW only at unity power factor (PF 1.0), which is standard for modern UK inverters, if your home has poor power factor from old appliances, you might need a PF correction unit or risk tripping the inverter.
- Forgetting SEG registration limits A frequent oversight is registering the wrong export capacity with your supplier. The 4.99 kVA figure is the exact value your energy company needs for your Smart Export Guarantee application, getting it wrong could cap your payments at a lower rate or void your contract entirely.
Quick reference
- The Eco4990ES inverter delivers a maximum continuous AC output of 4.99 kVA, which is equivalent to 4.99 kW at unity power factor.
- This inverter is MCS certified under product number Eco4990ES, confirming its 4.99 kVA rating for UK solar installations.
- You can pair the Eco4990ES with a solar array of up to 6.5 kWp without voiding the inverter warranty or MCS certification.
- At typical UK electricity prices of 24p per kWh, the 4.99 kVA output can save a household roughly £570 yearly through self-consumption and SEG payments.
- Using the wrong kVA figure in your SEG application can reduce your export payments by up to 20% compared to the correct 4.99 kVA rating.
Frequently Asked Questions
The Eco4990ES inverter delivers 4.99 kVA continuous AC output. This figure is confirmed by its MCS registration in 2026.
It determines your maximum export capacity for SEG tariffs. The inverter can handle up to 6.5 kWp of solar panels.
No, it is designed for single-phase domestic installations. For three-phase homes, you may need a derated or different inverter.
