Solar PV is being installed today! I’ve been looking at Air Source Heat Pumps (ASHPs) but have decided to put this on hold until the Solar install beds in.
These are my thoughts on this form of heating our home:
•Our Gas Boiler is 87% efficient – so 87% of the energy from the gas is converted to heat and hot water. Pretty good for a gas boiler.
•An ASHP is up to 330% efficient, so nearly 4x more efficient.
•We used around 28,000 kWh of gas last year for heating and hot water.
•The equivalent ASHP would use around 9,000kWh of electricity to provide the same level of heating and hot water.
•From a green perspective, this is obviously very good as we’re using a fraction of the energy with a ¼ of the level of CO2 used.
I was confused about the concept of the ASHP being more than 100% efficient, but with a bit of research I found the following details:
Energy efficiency is often measured by the percentage of energy that is lost during its conversion and transfer processes. When we use traditional heating methods such as boilers or electric heating strips, a significant amount of potential energy is wasted through heat loss. This is because the radiant heat produced by these methods does not solely warm the air, but also dissipates through exhaust systems and leaks. As a result, homeowners receive less heat energy than the amount of energy required to generate it.
However, there is an exception to this inefficiency in the form of air source heat pumps. These pumps concentrate available heat energy from the surrounding environment and transfer it to where it’s needed, using only electricity as input. In fact, in optimal conditions, a heat pump can transfer up to 330 percent more energy than the electricity required to power it. As such, air source heat pumps are a much more energy-efficient option compared to traditional heating methods.
Usage and Costs
•Last year we used 11,176 kWh electricity – Up from the approx 10,000 the previous year. Partially due to the Hot Tub.
•With an ASHP, this would be slightly over 20,500kWh of electricity, but obviously zero gas usage. We also wouldn’t have the standing charge for gas.
•We’re also going to see a rise in electricity usage due to car charging.
•Our gas tariff is currently 10.20p/kWh and 26.84p/day standing charge.
•Electricity is more complicated, but currently the standing charge is 48.65p/day. From 23:30-05:30 our rate is 7.5p/kWh. For the other 18 hours of the day, the rate is 38.57p/kWh.
Electricity Generation and Usage
•Our Solar Panels are hopefully going to generate around 5800kWh of “Free” electricity per year, although a lot of this will be at times we don’t need to heat the house – During the day in summer time.
•We’re going to want to use most of our electricity during the night so we’re only paying 7.5p for it as opposed to 38.5p, so we’ll need to:
•Charge the cars overnight.
•Recharge the 15kW of batteries in the loft overnight.
•Heat the hot water.
•Heat the ground floor underfloor heating right up.
•We will then have full car and house batteries that we can use to power the house and maintain the heat.
•We’ll get around 6kWh of solar energy per day in January (26.5kWh per day in July), plus the 15kWh of cheap overnight power stored in the batteries.
•We’ll still have to use some expensive electricity during the day in Winter, but hopefully this will be limited.
When to Switch
•Ban on new gas boilers from 2025 with gas supply being phased out from 2030.
•Currently a government grant of £5000 which would cover just under half of the costs. Think this ends next March.
So whilst we’re going to need to do something in the next few years, and possibly before March next year, we’re going to wait for Solar install to bed in before getting ASHP.