800W Plug-In Solar Kit Output: London vs Athens Over 19 Years
About 933 kWh a year in London and 1,458 kWh a year in Athens. That is the 19 year average (2005 to 2023) for an 800W plug-in solar kit with two JA Solar 465W panels and a Hoymiles HMS-800-2WB microinverter, modelled with the EU's PVGIS satellite data. Athens produces 56% more, but London's output is steady: even its worst year delivered 874 kWh.
How much will an 800W plug-in solar kit output over a year? Customers ask us this constantly, and the honest answer is: it depends where the sun is. To show how much location matters, we modelled the same kit in two very different places, London and Athens. Instead of a single typical year, we used 19 years of hour by hour satellite weather data, so you can see the average and the bad years as well as the good ones.
The setup we modelled
| Component | Detail |
|---|---|
| Solar panels | 2 × JA Solar JAM54D41-465/LR, 465W each, 23.3% module efficiency, N-type double glass |
| Total panel power | 930Wp (watts peak, the rating under standard laboratory test conditions) |
| Microinverter | Hoymiles HMS-800-2WB, 800VA AC output, two independent MPPT inputs, 96.7% peak efficiency |
| Mounting | Fixed, facing roughly south, at the best tilt for each city (40° in London, 32° in Athens) |
| System losses | 14%, the PVGIS standard allowance for inverter conversion, cabling, dirt and ageing |
| Weather data | PVGIS 5.3, SARAH3 satellite irradiance and ERA5 temperature, hourly, 2005 to 2023 |
Does the 23% panel efficiency change the result? Not on its own. Efficiency tells you how much power you get per square metre of panel, not per watt. Two 465W panels at 23% produce the same energy as 930W of less efficient panels; they just take up less space on a balcony, wall or patio.
London vs Athens: energy produced in 365 days
| Result (2005 to 2023) | London | Athens |
|---|---|---|
| Average energy per year | 933 kWh | 1,458 kWh |
| Average per day | 2.6 kWh | 4.0 kWh |
| Worst year | 874 kWh (2021) | 1,394 kWh (2010) |
| Best year | 1,018 kWh (2022) | 1,518 kWh (2022) |
| Year to year variation (standard deviation) | ±39 kWh | ±34 kWh |
| Sunlight on the panels per year | 1,264 kWh/m² | 2,035 kWh/m² |
| Energy per kWp installed | 1,003 kWh/kWp | 1,567 kWh/kWp |
Athens gets about 61% more sunlight on the panels, but produces 56% more energy. The difference is heat, which we explain below.
Month by month: where the gap opens up
| Month | London (kWh) | Athens (kWh) |
|---|---|---|
| January | 38 | 86 |
| February | 50 | 90 |
| March | 79 | 124 |
| April | 105 | 137 |
| May | 108 | 144 |
| June | 110 | 146 |
| July | 112 | 158 |
| August | 101 | 157 |
| September | 87 | 133 |
| October | 63 | 115 |
| November | 45 | 89 |
| December | 34 | 79 |
From April to July, London produces about 70 to 80% of what Athens does. The big difference is in winter: in December and January, Athens produces more than twice as much. If you are in the UK, roughly two thirds of your yearly energy arrives between April and September, so the kit is at its most useful in spring and summer.
See every year from 2005 to 2023
| Year | London (kWh) | Athens (kWh) |
|---|---|---|
| 2005 | 885 | 1,428 |
| 2006 | 936 | 1,447 |
| 2007 | 965 | 1,495 |
| 2008 | 904 | 1,463 |
| 2009 | 937 | 1,394 |
| 2010 | 887 | 1,394 |
| 2011 | 949 | 1,442 |
| 2012 | 918 | 1,450 |
| 2013 | 878 | 1,464 |
| 2014 | 984 | 1,410 |
| 2015 | 935 | 1,451 |
| 2016 | 917 | 1,471 |
| 2017 | 898 | 1,502 |
| 2018 | 968 | 1,451 |
| 2019 | 955 | 1,474 |
| 2020 | 987 | 1,509 |
| 2021 | 874 | 1,472 |
| 2022 | 1,018 | 1,518 |
| 2023 | 938 | 1,459 |
Why Athens is not 61% better: heat costs power
Solar panels lose a little output as they warm up. PVGIS estimates that temperature costs this kit about 4.8% of its yearly energy in London and about 8.0% in Athens, where the panels run hotter in summer. London also gains slightly (about 1.9%) from the spectrum of its diffuse, cloudy light. That is why Athens gets 61% more sunlight but only 56% more energy.
N-type panels such as the JA Solar 465W have a lower temperature coefficient than older panel types, which helps in warm climates. Leaving an air gap behind the panels helps too.
Does the 800W limit waste energy from a 930W array?
Hardly at all. In the UK, a plug-in kit must stay within an 800VA output, so the Hoymiles HMS-800-2WB caps what it delivers at 800W. In theory, 930W of panels could produce more than that.
In practice, panels rarely reach their full rating outdoors because of heat, light angle and system losses. In 19 years of hourly data, the highest hour in London reached about 833W and in Athens about 871W. Output was above 800W for only around 2 hours a year in London and 5 hours a year in Athens. The energy lost to the cap was less than 0.1% in either city.
Why oversize the panels then? The extra 130W lifts output on the many hours that are not perfect: mornings, evenings, hazy days and winter. That is where a UK system earns most of its energy, so a 930W array on an 800W microinverter is a deliberate, sensible design. Hourly data averages out very short bright spells, so the real clipping loss may be slightly higher, but it remains small.
What the numbers mean for a UK home
- 933 kWh a year is about 2.6 kWh a day on average, from roughly 1 kWh a day in December to 3.6 kWh a day in July.
- A plug-in kit has no battery, so it saves most when you use the power as it is made: the fridge, freezer, router, home office equipment, and appliances such as the washing machine run during the day.
- To estimate your saving, multiply the kWh you use directly by your electricity unit rate. For example, if you used 600 kWh of the 933 kWh yourself at 25p per kWh, that would be £150 a year. Your own figure depends on your tariff and when you use electricity.
- Panels age slowly. JA Solar's warranty allows for 1% loss in the first year and 0.4% a year after that, so expect output a little below these figures as the system gets older.
Your result will differ from these figures if your panels face east or west, sit flat on the ground or upright on a balcony rail, or are shaded by trees or buildings. A balcony mount at a steep angle can produce noticeably less than the optimum tilt modelled here. Run PVGIS for your own address and angle, or ask us for help sizing the right kit.
For the rules on connecting a kit at home, read our guide Is plug-in solar legal in the UK? The 800VA rule explained. For larger systems, see how much energy you can produce at home from solar panels.
Common questions
How much electricity does an 800W plug-in solar kit produce in the UK?
With two 465W panels facing south at a good angle in London, about 933 kWh a year on average, based on 19 years of PVGIS data. Northern England and Scotland will be lower, and the south west a little higher. East or west facing, shaded or vertical panels will produce less.
Why use 19 years of data instead of one typical year?
Weather changes from year to year. Over 2005 to 2023, London ranged from 874 to 1,018 kWh and Athens from 1,394 to 1,518 kWh. Seeing the range is more useful than one number, because it tells you what a poor summer really costs.
Does the microinverter's efficiency make a big difference?
Only a small one. The Hoymiles HMS-800-2WB is rated at 96.7% peak efficiency, and inverter losses are included in the 14% system loss we used. Panel orientation, tilt and shade have a much larger effect on the yearly total.
Would a bigger microinverter produce more energy?
In this setup, barely, because the 800W cap costs less than 0.1% a year. In the UK, a plug-in kit must also stay within 800VA, so a larger inverter is not an option for plug-in use.
How do I check the yield for my own home?
Use the free PVGIS tool from the European Commission's Joint Research Centre. Enter your location, 0.93 kWp of panels, 14% system loss and your real tilt and direction. It gives monthly and yearly estimates for your exact site.
Get the kit we modelled
The VOLTACON Power 800W kit uses the same two JA Solar 465W panels and the Hoymiles HMS-800-2WB microinverter modelled in this article, with a ground mount and cabling included. The complete kit is on the ENA Type Test Register.
See the VOLTACON Power 800W plug-in solar kit
Prefer to supply your own mounting? See the 800W kit with Hoymiles HMS-800-2WB and 2 × JA Solar 465W, or the JA Solar 465W panel on its own.
Source: European Commission Joint Research Centre, PVGIS 5.3, PVGIS-SARAH3 radiation and ERA5 temperature data, hourly series 2005 to 2023, retrieved October 2026. London modelled at 51.507°N, 0.128°W (40° tilt, 6° east of south); Athens at 37.984°N, 23.728°E (32° tilt, 1° east of south); 0.93 kWp crystalline silicon, 14% system loss, free standing mounting. Results are modelled estimates, not a guarantee of output. Component figures are from the product listings on this site. This is general information, not installation advice: follow the kit instructions and your local regulations, and use a qualified electrician if you are unsure about your wiring.
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