The inverter is the heart of a solar system. It turns the panels' direct current into the alternating current your sockets use, and its type decides what happens when the grid goes off. Choosing the wrong type is one of the most common and costly mistakes in Kenyan solar.
On-grid (grid-tie) inverters
An on-grid inverter runs alongside the KPLC supply. Solar power is used first, and the grid supplies the rest.
- No battery, so it is the cheapest way to cut a daytime bill.
- It switches off during a KPLC outage. This is a safety requirement: an inverter must not feed power into lines that technicians may be working on. Many buyers are surprised to find their new solar system dark during a blackout.
- Best for offices, shops, factories and schools where most use is in daylight and outages are rare or covered by a generator.
Off-grid inverters
An off-grid system has no grid connection. Panels charge a battery, and the inverter supplies the site from the battery and the panels.
- Works anywhere, including sites far from KPLC lines.
- Needs a battery sized for the night and an array sized for the cloudy months, often with a generator for backup.
- Best for rural homes, farms, lodges, clinics and telecom sites without a grid connection. See our diesel generator vs solar hybrid article for an off-grid business example.
Hybrid inverters
A hybrid inverter combines both: it uses solar first, stores surplus in a battery, draws on the grid when needed, and keeps essential circuits running during an outage.
- Backup during outages, switching over automatically, usually within a fraction of a second.
- Flexible: it can start with a small battery and add more later, and can charge the battery from the grid at cheaper night rates if that ever makes sense.
- Best for homes and businesses with frequent outages, or that want to use solar in the evening.
Side by side
| On-grid | Off-grid | Hybrid | |
|---|---|---|---|
| Needs a KPLC connection | Yes | No | Optional, usually yes |
| Battery | None | Essential | Optional to large |
| Works during a KPLC outage | No | Not affected | Yes, on backed-up circuits |
| Relative cost | Lowest | Highest per kWh | Middle to high |
| Typical use | Daytime bill savings | Sites without grid | Savings plus backup |
Sizing the inverter
Three checks decide the size:
- The array. Inverters are usually paired with an array up to about 25% larger than their rating, because panels rarely produce their full rating in real conditions. A 5 kW inverter suits up to about 6.2 kW of panels (ten 620 W panels).
- The load it must run. For a hybrid or off-grid inverter, the continuous rating should be at least 25% above the essential load it carries during an outage or at night.
- Starting surges. Fridges, freezers and pumps draw several times their running power for a moment at start-up. Check the inverter's surge rating against the largest motor.
Common sizes are 3, 5, 6, 8 and 10 kW for homes and small businesses, and 15 kW and above, often three-phase, for larger sites.
Questions to ask the installer
- What happens to each circuit when KPLC power goes off?
- Is the inverter set so it does not export power to the grid, unless an export arrangement with Kenya Power is in place?
- Can I add batteries or panels later, and up to what size?
- Who handles warranty claims, and how long does a replacement take?
Choose with your numbers
- The free solar calculator suggests an inverter size from your array and essential load.
- Battery backup for KPLC outages and lithium vs lead-acid batteries cover the battery side.
- See how sizing works for how StimaPulse checks inverter, panel and battery compatibility.