Risemead Posted January 22, 2023 Share Posted January 22, 2023 Ours is a Flat roofed new build (600 sqm), the shell will be ready by Feb'23. We plan to install MVHR (Vent Axia) & ASHP (16 & 12kW Samsung Monobloc Heat Pump & a 400/130L Pre-Plumb - 4 Zone Cylinder). We also wanted to do Solar to the max possible. Our intention is not to sell anything back to the grid and want to be kind of self-sufficient and use it from the battery storage. If we have an average usage of around 22kw, what is the solar panel size needed? I am thinking of going for around 25kw battery storage. Link to comment Share on other sites More sharing options...
JohnMo Posted January 22, 2023 Share Posted January 22, 2023 I would be addressing your insulation values if you need that much power to heat your house. Whatever PV you install will give an abundance of electric April to September and then next to nothing when you need the most. Mid winter you can goes days with zero output. Also you really need to see, what lots of solar will cost you (payment to DNO) and if they actually let you. Your best bet is G99 route to approval, which limits export below 16A. You will need to ask for permission prior to install/ switching on. If you are connected to the grid permission is mandatory irrespective of your intension to export or otherwise. Same can also be true for your battery depending on how it hooked up. Link to comment Share on other sites More sharing options...
Andehh Posted January 22, 2023 Share Posted January 22, 2023 Please post up more... Flat roof.... 600sqm...25kwh of storage.. Wowee.... Prob need around 16kw of pv to make the most of that! Your DNO needs approaching ASAP on permissions... Some can be several weeks behind on their workload.... Link to comment Share on other sites More sharing options...
Risemead Posted January 22, 2023 Author Share Posted January 22, 2023 3 hours ago, JohnMo said: I would be addressing your insulation values if you need that much power to heat your house. Whatever PV you install will give an abundance of electric April to September and then next to nothing when you need the most. Mid winter you can goes days with zero output. Also you really need to see, what lots of solar will cost you (payment to DNO) and if they actually let you. Your best bet is G99 route to approval, which limits export below 16A. You will need to ask for permission prior to install/ switching on. If you are connected to the grid permission is mandatory irrespective of your intension to export or otherwise. Same can also be true for your battery depending on how it hooked up. Our insulation is 75mm Celotex, and all three floors will have underfloor heating and triple glazing. This should keep the house warm, reducing the average energy usage to less than 20kw (I hope). Regardless of whether we export energy or not, do we still need permission from the grid? Link to comment Share on other sites More sharing options...
Risemead Posted January 22, 2023 Author Share Posted January 22, 2023 3 hours ago, Andehh said: Please post up more... Flat roof.... 600sqm...25kwh of storage.. Wowee.... Prob need around 16kw of pv to make the most of that! Your DNO needs approaching ASAP on permissions... Some can be several weeks behind on their workload.... The first floor roof space will be around 155 sqm (we do have some more flat roof on the GF but not sure if they would install there? Do you think 16kw Pv can go in 155sqm of flat roof? Link to comment Share on other sites More sharing options...
Andehh Posted January 28, 2023 Share Posted January 28, 2023 It would need to be a very big roof. Probably talking 45 odd panels, some are 1.5sqm each ish....big roof required! Also what direction, if all facing 35 degree south unshaded is a big difference vs north facing with a chimney next to them casting shade! Link to comment Share on other sites More sharing options...
Conor Posted January 28, 2023 Share Posted January 28, 2023 (edited) On 22/01/2023 at 19:39, Risemead said: Our insulation is 75mm Celotex, and all three floors will have underfloor heating and triple glazing. This should keep the house warm, reducing the average energy usage to less than 20kw (I hope). Regardless of whether we export energy or not, do we still need permission from the grid? You sure about the 75mm celotex? It's about half of what you ideally want. Our ICF walls are 250mm grey EPS which is comparable to 130-150mm PIR. What's the build up? Block cavity? I'm assuming you've a healthy budget for a little more insulation. If you insulated to the passive house standards then you be needing closer to a single 12kW heat pump. There's £6k saved from the off plus probably thousands more per year in electric, as there is no way you can run off PV in the winter for that kind of heating load. 28kW of heating over 600m² is more than double what most people here get away with. (We're 350m², 9kW) For a flat roof the spacing of panels is much grater than pitched roof and IICR you get about half the density of panels. So let's say you have 80m² of usable space (allowing for roof lights etc) then you should get about 30 panels in, and at 350w each would give you about 11pkW. Now's the time to speak to an installer / supplier and your engineer and architect about a design, as the details will determine what you can get. And of course your DNO for a beefy supply. Edited January 28, 2023 by Conor Link to comment Share on other sites More sharing options...
Risemead Posted February 17, 2023 Author Share Posted February 17, 2023 thank you, appreciate your detailed reply Link to comment Share on other sites More sharing options...
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